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scons (1)

Name

scons - a software construction tool

Synopsis

scons [options...] [name=val...] [targets...]

Description

SCONS(1)                          SCons 4.2.0                         SCONS(1)



NAME
       scons - a software construction tool

SYNOPSIS
       scons [options...] [name=val...] [targets...]

DESCRIPTION
       scons orchestrates the construction of software (and other tangible
       products such as documentation files) by determining which component
       pieces must be built or rebuilt and invoking the necessary commands to
       build them.  SCons offers many features to improve developer
       productivity such as parallel builds, caching of build artifacts,
       automatic dependency scanning, and a database of information about
       previous builds so details do not have to be recalculated each run.

       scons requires Python 3.5 or later to run; there should be no other
       dependencies or requirements.
        Support for Python 3.5 is deprecated since SCons 4.2 and will be
       dropped in a future release. The CPython project has retired 3.5:
       https://www.python.org/dev/peps/pep-0478.

       You set up an SCons build system by writing a script that describes
       things to build (targets), and, if necessary, the rules to build those
       files (actions).  SCons comes with a collection of Builder methods
       which apply premade actions for building many common software
       components such as executable programs, object files and libraries, so
       that for many software projects, only the targets and input files
       (sources) need be specified in a call to a builder.  scons thus can
       operate at a level of abstraction above that of pure files. For example
       if you specify a library target named "foo", scons keeps track of the
       actual operating system dependent filename (such as libfoo.so on a
       GNU/Linux system), and how to refer to that library in later
       construction steps that want to use it, so you don't have to specify
       that precise information yourself.  scons can also scan automatically
       for dependency information, such as header files included by source
       code files, so this does not have to be specified manually.

       When invoked, scons looks for a file named SConstruct in the current
       directory and reads the build configuration from that file (other names
       are allowed, see the section called "SConscript Files" for more
       information). The SConstruct file may specify subsidiary configuration
       files by calling the SConscript function. By convention, these
       subsidiary files are named SConscript, although any name may be used.
       As a result of this naming convention, the term SConscript files is
       used to refer generically to the complete set of configuration files
       for a project (including the SConstruct file), regardless of the actual
       file names or number of such files.

       Before reading the SConscript files, scons looks for a directory named
       site_scons in various system directories and in the directory
       containing the SConstruct file or, if specified, the directory from the
       --site-dir option instead, and prepends the ones it finds to the Python
       module search path (sys.path), thus allowing modules in such
       directories to be imported in the normal Python way in SConscript
       files. For each found site directory, (1) if it contains a file
       site_init.py that file is evaluated, and (2) if it contains a directory
       site_tools the path to that directory is prepended to the default
       toolpath. See the --site-dir and --no-site-dir options for details on
       default paths and controlling the site directories.

       SConscript files are written in the Python programming language,
       although it is normally not necessary to be a Python programmer to use
       scons effectively. SConscript files are invoked in a context that makes
       the facilities described in this manual page available in their local
       namespace without any special steps. Standard Python scripting
       capabilities such as flow control, data manipulation, and imported
       Python libraries are available to use to handle complicated build
       situations. Other Python files can be made a part of the build system,
       but they do not automatically have the SCons context and need to import
       it if they need access (described later).

       scons reads and executes all of the included SConscript files before it
       begins building any targets. To make this clear, scons prints the
       following messages about what it is doing:

           $ scons foo.out
           scons: Reading SConscript files ...
           scons: done reading SConscript files.
           scons: Building targets  ...
           cp foo.in foo.out
           scons: done building targets.
           $

       The status messages (lines beginning with the scons: tag) may be
       suppressed using the -Q option.

       scons does not automatically propagate the external environment used to
       execute scons to the commands used to build target files. This is so
       that builds will be guaranteed repeatable regardless of the environment
       variables set at the time scons is invoked. This also means that if the
       compiler or other commands that you want to use to build your target
       files are not in standard system locations, scons will not find them
       unless you explicitly include the locations into the execution
       environment by setting the path in the ENV construction variable in the
       internal construction environment:

           import os
           env = Environment(ENV={'PATH': os.environ['PATH']})

       Similarly, if the commands use specific external environment variables
       that scons does not recognize, they can be propagated into the
       execution environment:

           import os

           env = Environment(
               ENV={
                   'PATH': os.environ['PATH'],
                   'ANDROID_HOME': os.environ['ANDROID_HOME'],
                   'ANDROID_NDK_HOME': os.environ['ANDROID_NDK_HOME'],
               }
           )

       Or you may explicitly propagate the invoking user's complete external
       environment:

           import os
           env = Environment(ENV=os.environ.copy())

       This comes at the expense of making your build dependent on the user's
       environment being set correctly, but it may be more convenient for many
       configurations. It should not cause problems if done in a build setup
       which tightly controls how the environment is set up before invoking
       scons, as in many continuous integration setups.

       scons can scan known input file types automatically for dependency
       information (for example, #include preprocessor directives in C or C++
       files) and will rebuild dependent files appropriately whenever any
       "included" input file changes.  scons supports the ability to define
       new scanners to support additional input file types.

       scons is normally executed in a top-level directory containing an
       SConstruct file. When scons is invoked, the command line (including the
       contents of the SCONSFLAGS environment variable, if set) is processed.
       Command-line options (see the section called "OPTIONS") are consumed.
       Any variable argument assignments are collected, and remaining
       arguments are taken as targets to build.

       Values of variables to be passed to the SConscript files may be
       specified on the command line:

           scons debug=1

       These variables are available through the ARGUMENTS dictionary, and can
       be used in the SConscript files to modify the build in any way:

           if ARGUMENTS.get('debug', 0):
               env = Environment(CCFLAGS='-g')
           else:
               env = Environment()

       The command-line variable arguments are also available in the ARGLIST
       list, indexed by their order on the command line. This allows you to
       process them in order rather than by name, if necessary. Each ARGLIST
       entry is a tuple containing (argname, argvalue).

       See the section called "Command-Line Construction Variables" for more
       information.

       scons can maintain a cache of target (derived) files that can be shared
       between multiple builds. When derived-file caching is enabled in an
       SConscript file, any target files built by scons will be copied to the
       cache. If an up-to-date target file is found in the cache, it will be
       retrieved from the cache instead of being rebuilt locally. Caching
       behavior may be disabled and controlled in other ways by the
       --cache-force, --cache-disable, --cache-readonly, and --cache-show
       command-line options. The --random option is useful to prevent multiple
       builds from trying to update the cache simultaneously.

       By default, scons searches for known programming tools on various
       systems and initializes itself based on what is found. On Windows
       systems which identify as win32, scons searches in order for the
       Microsoft Visual C++ tools, the MinGW tool chain, the Intel compiler
       tools, and the PharLap ETS compiler. On Windows system which identify
       as cygwin (that is, if scons is invoked from a cygwin shell), the order
       changes to prefer the GCC toolchain over the MSVC tools. On OS/2
       systems, scons searches in order for the OS/2 compiler, the GCC tool
       chain, and the Microsoft Visual C++ tools, On SGI IRIX, IBM AIX,
       Hewlett Packard HP-UX, and Oracle Solaris systems, scons searches for
       the native compiler tools (MIPSpro, Visual Age, aCC, and Forte tools
       respectively) and the GCC tool chain. On all other platforms, including
       POSIX (Linux and UNIX) platforms, scons searches in order for the GCC
       tool chain, and the Intel compiler tools. These default values may be
       overridden by appropriate setting of construction variables.

   Target Selection
       SCons acts on the selected targets, whether the requested operation is
       build, no-exec or clean. Targets are selected as follows:

        1. Targets specified on the command line. These may be files,
           directories, or phony targets defined using the Alias function.
           Directory targets are scanned by scons for any targets that may be
           found with a destination in or under that directory. The targets
           listed on the command line are made available in the
           COMMAND_LINE_TARGETS list.

        2. If no targets are specified on the command line, scons will select
           those targets specified in the SConscript files via calls to the
           Default function. These are known as the default targets, and are
           made available in the DEFAULT_TARGETS list.

        3. If no targets are selected by the previous steps, scons selects the
           current directory for scanning, unless command-line options which
           affect the target scan are detected (-C, -D, -u, -U). Since targets
           thus selected were not the result of user instructions, this target
           list is not made available for direct inspection; use the
           --debug=explain option if they need to be examined.

        4.  scons always adds to the selected targets any intermediate targets
           which are necessary to build the specified ones. For example, if
           constructing a shared library or dll from C source files, scons
           will also build the object files which will make up the library.

       To ignore the default targets specified through calls to Default and
       instead build all target files in or below the current directory
       specify the current directory (.) as a command-line target:

           scons .

       To build all target files, including any files outside of the current
       directory, supply a command-line target of the root directory (on POSIX
       systems):

           scons /

       or the path name(s) of the volume(s) in which all the targets should be
       built (on Windows systems):

           scons C:\ D:\

       A subset of a hierarchical tree may be built by remaining at the
       top-level directory (where the SConstruct file lives) and specifying
       the subdirectory as the target to build:

           scons src/subdir

       or by changing directory and invoking scons with the -u option, which
       traverses up the directory hierarchy until it finds the SConstruct
       file, and then builds targets relatively to the current subdirectory
       (see also the related -D and -U options):

           cd src/subdir
           scons -u .

       In all cases, more files may be built than are requested, as scons
       needs to make sure any dependent files are built.

       Specifying "cleanup" targets in SConscript files is usually not
       necessary. The -c flag removes all selected targets:

           scons -c .

       to remove all target files in or under the current directory, or:

           scons -c build export

       to remove target files under build and export.

       Additional files or directories to remove can be specified using the
       Clean function in the SConscript files. Conversely, targets that would
       normally be removed by the -c invocation can be retained by calling the
       NoClean function with those targets.

       scons supports building multiple targets in parallel via a -j option
       that takes, as its argument, the number of simultaneous tasks that may
       be spawned:

           scons -j 4

       builds four targets in parallel, for example.

OPTIONS
       In general, scons supports the same command-line options as GNU Make
       and many of those supported by cons.

       -b
           Ignored for compatibility with non-GNU versions of Make

       -c, --clean, --remove
           Set clean mode. Clean up by removing the selected targets, well as
           any files or directories associated with a selected target through
           calls to the Clean function. Will not remove any targets which are
           marked for preservation through calls to the NoClean function.

           While clean mode removes targets rather than building them, work
           which is done directly in Python code in SConscript files will
           still be carried out. If it is important to avoid some such work
           from taking place in clean mode, it should be protected. An
           SConscript file can determine which mode is active by querying
           GetOption, as in the call if GetOption("clean"):

       --cache-debug=file
           Write debug information about derived-file caching to the specified
           file. If file is a hyphen (-), the debug information is printed to
           the standard output. The printed messages describe what
           signature-file names are being looked for in, retrieved from, or
           written to the derived-file cache specified by CacheDir.

       --cache-disable, --no-cache
           Disable derived-file caching.  scons will neither retrieve files
           from the cache nor copy files to the cache. This option can be used
           to temporarily disable the cache without modifying the build
           scripts.

       --cache-force, --cache-populate
           When using CacheDir, populate a derived-file cache by copying any
           already-existing, up-to-date derived files to the cache, in
           addition to files built by this invocation. This is useful to
           populate a new cache with all the current derived files, or to add
           to the cache any derived files recently built with caching disabled
           via the --cache-disable option.

       --cache-readonly
           Use the derived-file cache, if enabled, to retrieve files, but do
           not not update the cache with any files actually built during this
           invocation.

       --cache-show
           When using a derived-file cache show the command that would have
           been executed to build the file (or the corresponding *COMSTR
           contents if set) even if the file is retrieved from cache. Without
           this option, scons shows a cache retrieval message if the file is
           fetched from cache. This allows producing consistent output for
           build logs, regardless of whether a target file was rebuilt or
           retrieved from the cache.

       --config=mode
           Control how the Configure call should use or generate the results
           of configuration tests.  mode should be one of the following
           choices:

           auto
               SCons will use its normal dependency mechanisms to decide if a
               test must be rebuilt or not. This saves time by not running the
               same configuration tests every time you invoke scons, but will
               overlook changes in system header files or external commands
               (such as compilers) if you don't specify those dependecies
               explicitly. This is the default behavior.

           force
               If this mode is specified, all configuration tests will be
               re-run regardless of whether the cached results are out of
               date. This can be used to explicitly force the configuration
               tests to be updated in response to an otherwise unconfigured
               change in a system header file or compiler.

           cache
               If this mode is specified, no configuration tests will be rerun
               and all results will be taken from cache.  scons will report an
               error if --config=cache is specified and a necessary test does
               not have any results in the cache.


       -C directory, --directory=directory
           Run as if scons was started in directory instead of the current
           working directory. That is, change directory before searching for
           the SConstruct, Sconstruct, sconstruct, SConstruct.py,
           Sconstruct.py or sconstruct.py file or doing anything else. When
           multiple -C options are given, each subsequent non-absolute -C
           directory is interpreted relative to the preceding one. This option
           is similar to using -f directory/SConstruct, but -f does not search
           for any of the predefined SConstruct names in the specified
           directory. See also options -u, -U and -D to change the SConstruct
           search behavior when this option is used.

       -D
           Works exactly the same way as the -u option except for the way
           default targets are handled. When this option is used and no
           targets are specified on the command line, all default targets are
           built, whether or not they are below the current directory.

       --debug=type[,type...]
           Debug the build process.  type specifies the kind of debugging info
           to emit. Multiple types may be specified, separated by commas. The
           following types are recognized:

           action-timestamps
               Prints additional time profiling information. For each command,
               shows the absolute start and end times. This may be useful in
               debugging parallel builds. Implies the --debug=time option.

               Available since scons 3.1.

           count
               Print how many objects are created of the various classes used
               internally by SCons before and after reading the SConscript
               files and before and after building targets. This is not
               supported when SCons is executed with the Python -O (optimized)
               option or when the SCons modules have been compiled with
               optimization (that is, when executing from *.pyo files).

           duplicate
               Print a line for each unlink/relink (or copy) of a variant file
               from its source file. Includes debugging info for unlinking
               stale variant files, as well as unlinking old targets before
               building them.

           explain
               Print an explanation of why scons is deciding to (re-)build the
               targets it selects for building.

           findlibs
               Instruct the scanner that searches for libraries to print a
               message about each potential library name it is searching for,
               and about the actual libraries it finds.

           includes
               Print the include tree after each top-level target is built.
               This is generally used to find out what files are included by
               the sources of a given derived file:

                   $ scons --debug=includes foo.o

           memoizer
               Prints a summary of hits and misses using the Memoizer, an
               internal subsystem that counts how often SCons uses cached
               values in memory instead of recomputing them each time they're
               needed.

           memory
               Prints how much memory SCons uses before and after reading the
               SConscript files and before and after building targets.

           objects
               Prints a list of the various objects of the various classes
               used internally by SCons.

           pdb
               Re-run scons under the control of the pdb Python debugger.

           prepare
               Print a line each time any target (internal or external) is
               prepared for building.  scons prints this for each target it
               considers, even if that target is up to date (see also
               --debug=explain). This can help debug problems with targets
               that aren't being built; it shows whether scons is at least
               considering them or not.

           presub
               Print the raw command line used to build each target before the
               construction environment variables are substituted. Also shows
               which targets are being built by this command. Output looks
               something like this:

                   $ scons --debug=presub
                   Building myprog.o with action(s):
                     $SHCC $SHCFLAGS $SHCCFLAGS $CPPFLAGS $_CPPINCFLAGS -c -o $TARGET $SOURCES
                   ...

           stacktrace
               Prints an internal Python stack trace when encountering an
               otherwise unexplained error.

           time
               Prints various time profiling information:

               o   The time spent executing each individual build command

               o   The total build time (time SCons ran from beginning to end)

               o   The total time spent reading and executing SConscript files

               o   The total time SCons itself spent running (that is, not
                   counting reading and executing SConscript files)

               o   The total time spent executing all build commands

               o   The elapsed wall-clock time spent executing those build
                   commands

               o   The time spent processing each file passed to the
                   SConscript function

               (When scons is executed without the -j option, the elapsed
               wall-clock time will typically be slightly longer than the
               total time spent executing all the build commands, due to the
               SCons processing that takes place in between executing each
               command. When scons is executed with the -j option, and your
               build configuration allows good parallelization, the elapsed
               wall-clock time should be significantly smaller than the total
               time spent executing all the build commands, since multiple
               build commands and intervening SCons processing should take
               place in parallel.)


       --diskcheck=type
           Enable specific checks for whether or not there is a file on disk
           where the SCons configuration expects a directory (or vice versa)
           when searching for source and include files.  type can be an
           available diskcheck type or the special tokens all or none. A
           comma-separated string can be used to select multiple checks. The
           default setting is all.

           Current available checks are:

           match
               to check that files and directories on disk match SCons'
               expected configuration.

           Disabling some or all of these checks can provide a performance
           boost for large configurations, or when the configuration will
           check for files and/or directories across networked or shared file
           systems, at the slight increased risk of an incorrect build or of
           not handling errors gracefully.

       --duplicate=ORDER
           There are three ways to duplicate files in a build tree: hard
           links, soft (symbolic) links and copies. The default policy is to
           prefer hard links to soft links to copies. You can specify a
           different policy with this option.  ORDER must be one of
           hard-soft-copy (the default), soft-hard-copy, hard-copy, soft-copy
           or copy.  SCons will attempt to duplicate files using the
           mechanisms in the specified order.

       --enable-virtualenv
           Import virtualenv-related variables to SCons.

       --experimental=feature
           Enable experimental features and/or tools.  feature can be an
           available feature name or the special tokens all or none. A
           comma-separated string can be used to select multiple features. The
           default setting is none.

           Current available features are: ninja.

               Caution
               No Support offered for any features or tools enabled by this
               flag.
           Available since scons 4.2.

       -f file, --file=file, --makefile=file, --sconstruct=file
           Use file as the initial SConscript file. Multiple -f options may be
           specified, in which case scons will read all of the specified
           files.

       -h, --help
           Print a local help message for this project, if one is defined in
           the SConscript files (see the Help function), plus a line that
           refers to the standard SCons help message. If no local help message
           is defined, prints the standard SCons help message (as for the -H
           option) plus help for any local options defined through AddOption.
           Exits after displaying the appropriate message.

           Note that use of this option requires SCons to process the
           SConscript files, so syntax errors may cause the help message not
           to be displayed.

       --hash-chunksize=KILOBYTES
           Set the block size used when computing content signatures to
           KILOBYTES. This value determines the size of the chunks which are
           read in at once when computing signature hashes. Files below that
           size are fully stored in memory before performing the signature
           computation while bigger files are read in block-by-block. A huge
           block-size leads to high memory consumption while a very small
           block-size slows down the build considerably.

           The default value is to use a chunk size of 64 kilobytes, which
           should be appropriate for most uses.

           Available since scons 4.2.

       --hash-format=ALGORITHM
           Set the hashing algorithm used by SCons to ALGORITHM. This value
           determines the hashing algorithm used in generating content
           signatures or CacheDir keys.

           The supported list of values are: md5, sha1, and sha256. However,
           the Python interpreter used to run SCons must have the
           corresponding support available in the hashlib module to use the
           specified algorithm.

           Specifying this value changes the name of the SConsign database.
           For example, --hash-format=sha256 will create a SConsign database
           with name .sconsign_sha256.dblite.

           If this option is not specified, a hash format of md5 is used, and
           the SConsign database is .sconsign.dblite.

           Available since scons 4.2.

       -H, --help-options
           Print the standard help message about SCons command-line options
           and exit.

       -i, --ignore-errors
           Ignore all errors from commands executed to rebuild files.

       -I directory, --include-dir=directory
           Specifies a directory to search for imported Python modules. If
           several -I options are used, the directories are searched in the
           order specified.

       --ignore-virtualenv
           Suppress importing virtualenv-related variables to SCons.

       --implicit-cache
           Cache implicit dependencies. This causes scons to use the implicit
           (scanned) dependencies from the last time it was run instead of
           scanning the files for implicit dependencies. This can
           significantly speed up SCons, but with the following limitations:

           scons will not detect changes to implicit dependency search paths
           (e.g.  CPPPATH, LIBPATH) that would ordinarily cause different
           versions of same-named files to be used.

           scons will miss changes in the implicit dependencies in cases where
           a new implicit dependency is added earlier in the implicit
           dependency search path (e.g.  CPPPATH, LIBPATH) than a current
           implicit dependency with the same name.

       --implicit-deps-changed
           Forces SCons to ignore the cached implicit dependencies. This
           causes the implicit dependencies to be rescanned and recached. This
           implies --implicit-cache.

       --implicit-deps-unchanged
           Force SCons to ignore changes in the implicit dependencies. This
           causes cached implicit dependencies to always be used. This implies
           --implicit-cache.

       --install-sandbox=sandbox_path
           When using the Install builders, prepend sandbox_path to the
           installation paths such that all installed files will be placed
           under that directory. This option is unavailable if one of Install,
           InstallAs or InstallVersionedLib is not used in the SConscript
           files.

       --interactive
           Starts SCons in interactive mode. The SConscript files are read
           once and a scons>>> prompt is printed. Targets may now be rebuilt
           by typing commands at interactive prompt without having to re-read
           the SConscript files and re-initialize the dependency graph from
           scratch.

           SCons interactive mode supports the following commands:

           build [OPTIONS] [TARGETS] ...
               Builds the specified TARGETS (and their dependencies) with the
               specified SCons command-line OPTIONS.  b and scons are synonyms
               for build.

               The following SCons command-line options affect the build
               command:

                   --cache-debug=FILE
                   --cache-disable, --no-cache
                   --cache-force, --cache-populate
                   --cache-readonly
                   --cache-show
                   --debug=TYPE
                   -i, --ignore-errors
                   -j N, --jobs=N
                   -k, --keep-going
                   -n, --no-exec, --just-print, --dry-run, --recon
                   -Q
                   -s, --silent, --quiet
                   --taskmastertrace=FILE
                   --tree=OPTIONS

               Any other SCons command-line options that are specified do not
               cause errors but have no effect on the build command (mainly
               because they affect how the SConscript files are read, which
               only happens once at the beginning of interactive mode).

           clean [OPTIONS] [TARGETS] ...
               Cleans the specified TARGETS (and their dependencies) with the
               specified OPTIONS.  c is a synonym. This command is itself a
               synonym for build --clean

           exit
               Exits SCons interactive mode. You can also exit by terminating
               input (Ctrl+D UNIX or Linux systems, (Ctrl+Z on Windows
               systems).

           help [COMMAND]
               Provides a help message about the commands available in SCons
               interactive mode. If COMMAND is specified, h and ?  are
               synonyms.

           shell [COMMANDLINE]
               Executes the specified COMMANDLINE in a subshell. If no
               COMMANDLINE is specified, executes the interactive command
               interpreter specified in the SHELL environment variable (on
               UNIX and Linux systems) or the COMSPEC environment variable (on
               Windows systems).  sh and !  are synonyms.

           version
               Prints SCons version information.

           An empty line repeats the last typed command. Command-line editing
           can be used if the readline module is available.

               $ scons --interactive
               scons: Reading SConscript files ...
               scons: done reading SConscript files.
               scons>>> build -n prog
               scons>>> exit

       -j N, --jobs=N
           Specifies the maximum number of comcurrent jobs (commands) to run.
           If there is more than one -j option, the last one is effective.

       -k, --keep-going
           Continue as much as possible after an error. The target that failed
           and those that depend on it will not be remade, but other targets
           specified on the command line will still be processed.

       -m
           Ignored for compatibility with non-GNU versions of Make.

       --max-drift=SECONDS
           Set the maximum expected drift in the modification time of files to
           SECONDS. This value determines how long a file must be unmodified
           before its cached content signature will be used instead of
           calculating a new content signature (MD5 checksum) of the file's
           contents. The default value is 2 days, which means a file must have
           a modification time of at least two days ago in order to have its
           cached content signature used. A negative value means to never
           cache the content signature and to ignore the cached value if there
           already is one. A value of 0 means to always use the cached
           signature, no matter how old the file is.

       --md5-chunksize=KILOBYTES
           A deprecated synonym for --hash-chunksize.

           Deprecated since scons 4.2.

       -n, --no-exec, --just-print, --dry-run, --recon
           Set no execute mode. Print the commands that would be executed to
           build any out-of-date target files, but do not execute the
           commands.

           The output is a best effort, as SCons cannot always precisely
           determine what would be built. For example, if a file is generated
           by a builder action that is later used in the build, that file is
           not available to scan for dependencies on an unbuilt tree, or may
           contain out of date information in a built tree.

           Work which is done directly in Python code in SConscript files, as
           opposed to work done by builder actions during the build phase,
           will still be carried out. If it is important to avoid some such
           work from taking place in no execute mode, it should be protected.
           An SConscript file can determine which mode is active by querying
           GetOption, as in the call if GetOption("no_exec"):

       --no-site-dir
           Prevents the automatic addition of the standard site_scons dirs to
           sys.path. Also prevents loading the site_scons/site_init.py modules
           if they exist, and prevents adding their site_scons/site_tools dirs
           to the toolpath.

       --package-type=type
           The type or types of package to create when using the Package
           builder. In the case of multiple types, type should be a
           comma-separated string; SCons will try to build for all of those
           packages. Note this option is only available if the packaging tool
           has been enabled.

       --profile=file
           Run SCons under the Python profiler and save the results in the
           specified file. The results may be analyzed using the Python pstats
           module.

       -q, --question
           Do not run any commands, or print anything. Just return an exit
           status that is zero if the specified targets are already up to
           date, non-zero otherwise.

       -Q
           Quiets SCons status messages about reading SConscript files,
           building targets and entering directories. Commands that are
           executed to rebuild target files are still printed.

       --random
           Build dependencies in a random order. This is useful when building
           multiple trees simultaneously with caching enabled, to prevent
           multiple builds from simultaneously trying to build or retrieve the
           same target files.

       -s, --silent, --quiet
           Silent. Do not print commands that are executed to rebuild target
           files. Also suppresses SCons status messages.

       -S, --no-keep-going, --stop
           Ignored for compatibility with GNU Make

       --site-dir=dir
           Uses the named dir as the site directory rather than the default
           site_scons directories. This directory will be prepended to
           sys.path, the module dir/site_init.py will be loaded if it exists,
           and dir/site_tools will be added to the default toolpath.

           The default set of site_scons directories used when --site-dir is
           not specified depends on the system platform, as follows.
           Directories are examined in the order given, from most generic to
           most specific, so the last-executed site_init.py file is the most
           specific one (which gives it the chance to override everything
           else), and the directories are prepended to the paths, again so the
           last directory examined comes first in the resulting path.

           Windows:

                   %ALLUSERSPROFILE/Application Data/scons/site_scons
                   %USERPROFILE%/Local Settings/Application Data/scons/site_scons
                   %APPDATA%/scons/site_scons
                   %HOME%/.scons/site_scons
                   ./site_scons

           Mac OS X:

                   /Library/Application Support/SCons/site_scons
                   /opt/local/share/scons/site_scons (for MacPorts)
                   /sw/share/scons/site_scons (for Fink)
                   $HOME/Library/Application Support/SCons/site_scons
                   $HOME/.scons/site_scons
                   ./site_scons

           Solaris:

                   /opt/sfw/scons/site_scons
                   /usr/share/scons/site_scons
                   $HOME/.scons/site_scons
                   ./site_scons

           Linux, HPUX, and other Posix-like systems:

                   /usr/share/scons/site_scons
                   $HOME/.scons/site_scons
                   ./site_scons

       --stack-size=KILOBYTES
           Set the size stack used to run threads to KILOBYTES. This value
           determines the stack size of the threads used to run jobs. These
           threads execute the actions of the builders for the nodes that are
           out-of-date. This option has no effect unless the number of
           concurrent build jobs is larger than one (as set by -j N or
           --jobs=N on the command line or SetOption in a script).

           Using a stack size that is too small may cause stack overflow
           errors. This usually shows up as segmentation faults that cause
           scons to abort before building anything. Using a stack size that is
           too large will cause scons to use more memory than required and may
           slow down the entire build process. The default value is to use a
           stack size of 256 kilobytes, which should be appropriate for most
           uses. You should not need to increase this value unless you
           encounter stack overflow errors.

       -t, --touch
           Ignored for compatibility with GNU Make. (Touching a file to make
           it appear up-to-date is unnecessary when using scons.)

       --taskmastertrace=file
           Prints trace information to the specified file about how the
           internal Taskmaster object evaluates and controls the order in
           which Nodes are built. A file name of - may be used to specify the
           standard output.

       --tree=type[,type...]
           Prints a tree of the dependencies after each top-level target is
           built. This prints out some or all of the tree, in various formats,
           depending on the type specified:

           all
               Print the entire dependency tree after each top-level target is
               built. This prints out the complete dependency tree, including
               implicit dependencies and ignored dependencies.

           derived
               Restricts the tree output to only derived (target) files, not
               source files.

           linedraw
               Draw the tree output using Unicode line-drawing characters
               instead of plain ASCII text. This option acts as a modifier to
               the selected type(s). If specified alone, without any type, it
               behaves as if all had been specified.

               Available since scons 4.0.

           status
               Prints status information for each displayed node.

           prune
               Prunes the tree to avoid repeating dependency information for
               nodes that have already been displayed. Any node that has
               already been displayed will have its name printed in [square
               brackets], as an indication that the dependencies for that node
               can be found by searching for the relevant output higher up in
               the tree.

           Multiple type choices may be specified, separated by commas:

               # Prints only derived files, with status information:
               scons --tree=derived,status

               # Prints all dependencies of target, with status information
               # and pruning dependencies of already-visited Nodes:
               scons --tree=all,prune,status target

       -u, --up, --search-up
           Walks up the directory structure until an SConstruct, Sconstruct,
           sconstruct, SConstruct.py, Sconstruct.py or sconstruct.py file is
           found, and uses that as the top of the directory tree. If no
           targets are specified on the command line, only targets at or below
           the current directory will be built.

       -U
           Works exactly the same way as the -u option except for the way
           default targets are handled. When this option is used and no
           targets are specified on the command line, all default targets that
           are defined in the SConscript(s) in the current directory are
           built, regardless of what directory the resultant targets end up
           in.

       -v, --version
           Print the scons version, copyright information, list of authors,
           and any other relevant information. Then exit.

       -w, --print-directory
           Print a message containing the working directory before and after
           other processing.

       --no-print-directory
           Turn off -w, even if it was turned on implicitly.

       --warn=type, --warn=no-type
           Enable or disable (with the no- prefix) warnings.  type specifies
           the type of warnings to be enabled or disabled:

           all
               All warnings.

           cache-version
               Warnings about the derived-file cache directory specified by
               CacheDir not using the latest configuration information. These
               warnings are enabled by default.

           cache-write-error
               Warnings about errors trying to write a copy of a built file to
               a specified derived-file cache specified by CacheDir. These
               warnings are disabled by default.

           corrupt-sconsign
               Warnings about unfamiliar signature data in .sconsign files.
               These warnings are enabled by default.

           dependency
               Warnings about dependencies. These warnings are disabled by
               default.

           deprecated
               Warnings about use of currently deprecated features. These
               warnings are enabled by default. Not all deprecation warnings
               can be disabled with the --warn=no-deprecated option as some
               deprecated features which are late in the deprecation cycle may
               have been designated as mandatory warnings, and these will
               still display. Warnings for certain deprecated features may
               also be enabled or disabled individually; see below.

           duplicate-environment
               Warnings about attempts to specify a build of a target with two
               different construction environments that use the same action.
               These warnings are enabled by default.

           fortran-cxx-mix
               Warnings about linking Fortran and C++ object files in a single
               executable, which can yield unpredictable behavior with some
               compilers.

           future-deprecated
               Warnings about features that will be deprecated in the future.
               Such warnings are disabled by default. Enabling future
               deprecation warnings is recommended for projects that
               redistribute SCons configurations for other users to build, so
               that the project can be warned as soon as possible about
               to-be-deprecated features that may require changes to the
               configuration.

           link
               Warnings about link steps.

           misleading-keywords
               Warnings about the use of two commonly misspelled keywords
               targets and sources to Builder calls. The correct spelling is
               the singular form, even though target and source can themselves
               refer to lists of names or nodes.

           missing-sconscript
               Warnings about missing SConscript files. These warnings are
               enabled by default.

           no-object-count
               Warnings about the --debug=object feature not working when
               scons is run with the Python -O option or from optimized Python
               (.pyo) modules.

           no-parallel-support
               Warnings about the version of Python not being able to support
               parallel builds when the -j option is used. These warnings are
               enabled by default.

           python-version
               Warnings about running SCons with a deprecated version of
               Python. These warnings are enabled by default.

           reserved-variable
               Warnings about attempts to set the reserved construction
               variable names $CHANGED_SOURCES, $CHANGED_TARGETS, $TARGET,
               $TARGETS, $SOURCE, $SOURCES, $UNCHANGED_SOURCES or
               $UNCHANGED_TARGETS. These warnings are disabled by default.

           stack-size
               Warnings about requests to set the stack size that could not be
               honored. These warnings are enabled by default.

           target_not_build
               Warnings about a build rule not building the expected targets.
               These warnings are disabled by default.


       -Y repository, --repository=repository, --srcdir=repository
           Search the specified repository for any input and target files not
           found in the local directory hierarchy. Multiple -Y options may be
           specified, in which case the repositories are searched in the order
           specified.

SCONSCRIPT FILE REFERENCE
   SConscript Files
       The build configuration is described by one or more files, known as
       SConscript files. There must be at least one file for a valid build
       (scons will quit if it does not find one).  scons by default looks for
       this file by the name SConstruct in the directory from which you run
       scons, though if necessary, also looks for alternative file names
       Sconstruct, sconstruct, SConstruct.py, Sconstruct.py and sconstruct.py
       in that order. A different file name (which can include a pathname
       part) may be specified via the -f option. Except for the SConstruct
       file, these files are not searched for automatically; you add
       additional configuration files to the build by calling the SConscript
       function. This allows parts of the build to be conditionally included
       or excluded at run-time depending on how scons is invoked.

       Each SConscript file in a build configuration is invoked independently
       in a separate context. This provides necessary isolation so that
       different parts of the build don't accidentally step on each other. You
       have to be explicit about sharing information, by using the Export
       function or the exports argument to the SConscript function, as well as
       the Return function in a called SConscript file, and comsume shared
       information by using the Import function.

       The following sections describe the various SCons facilities that can
       be used in SConscript files. Quick links:
           Construction Environments
           Tools
           Builder Methods
           Methods and Functions to do Things
           SConscript Variables
           Construction Variables
           Configure Contexts
           Command-Line Construction Variables
           Node Objects

   Construction Environments
       A Construction Environment is the basic means by which SConscript files
       communicate build information to scons. A new construction environment
       is created using the Environment function:

           env = Environment()

       Construction environment attributes called Construction Variables may
       be set either by specifying them as keyword arguments when the object
       is created or by assigning them a value after the object is created.
       These two are nominally equivalent:

           env = Environment(FOO='foo')
           env['FOO'] = 'foo'

       Note that certain settings which affect tool detection are referenced
       only during initialization, and so need to be supplied as part of the
       call to Environment. For example, setting $MSVC_VERSION selects the
       version of Microsoft Visual C++ you wish to use, but setting it after
       the construction environment is constructed has no effect.

       As a convenience, construction variables may also be set or modified by
       the parse_flags keyword argument during object creation, which has the
       effect of the env.MergeFlags method being applied to the argument value
       after all other processing is completed. This is useful either if the
       exact content of the flags is unknown (for example, read from a control
       file) or if the flags need to be distributed to a number of
       construction variables.  env.ParseFlags describes how these arguments
       are distributed to construction variables.

           env = Environment(parse_flags='-Iinclude -DEBUG -lm')

       This example adds 'include' to the CPPPATH construction variable,
       'EBUG' to CPPDEFINES, and 'm' to LIBS.

       An existing construction environment can be duplicated by calling the
       env.Clone method. Without arguments, it will be a copy with the same
       settings. Otherwise, env.Clone takes the same arguments as Environment,
       and uses the arguments to create a modified copy.

       SCons provides a special construction environment called the Default
       Environment. The default environment is used only for global functions,
       that is, construction activities called without the context of a
       regular construction environment. See DefaultEnvironment for more
       information.

       By default, a new construction environment is initialized with a set of
       builder methods and construction variables that are appropriate for the
       current platform. The optional platform keyword argument may be used to
       specify that the construction environment should be initialized for a
       different platform:

           env = Environment(platform='cygwin')
           env = Environment(platform='os2')
           env = Environment(platform='posix')
           env = Environment(platform='win32')

       Specifying a platform initializes the appropriate construction
       variables in the environment to use and generate file names with
       prefixes and suffixes appropriate for that platform.

       Note that the win32 platform adds the SystemDrive and SystemRoot
       variables from the user's external environment to the construction
       environment's ENV dictionary. This is so that any executed commands
       that use sockets to connect with other systems (such as fetching source
       files from external CVS repository specifications like
       :pserver:anonymous@cvs.sourceforge.net:/cvsroot/scons) will work on
       Windows systems.

       The platform argument may be a function or callable object, in which
       case the Environment method will call it to update the new construction
       environment:

           def my_platform(env):
               env['VAR'] = 'xyzzy'

           env = Environment(platform=my_platform)

       The optional tools and toolpath keyword arguments affect the way tools
       available to the environment are initialized. See the section called
       "Tools" for details.

       The optional variables keyword argument allows passing a Variables
       object which will be used in the initialization of the construction
       environment See the section called "Command-Line Construction
       Variables" for details.

   Tools
       SCons has a large number of predefined tools (more properly, tool
       specifications) which are used to help initialize the construction
       environment. An scons tool is only responsible for setup. For example,
       if the SConscript file declares the need to construct an object file
       from a C-language source file by calling the Object builder, then a
       tool representing an available C compiler needs to have run first, to
       set up the builder and all the construction variables it needs in the
       associated construction environment; the tool itself is not called in
       the process of the build. Normally this happens invisibly: scons has
       per-platform lists of default tools, and it runs through those tools,
       calling the ones which are actually applicable, skipping those where
       necessary programs are not installed on the build system, or other
       preconditions are not met.

       A specific set of tools with which to initialize an environment when
       creating it may be specified using the optional keyword argument tools,
       which takes a list of tool names. This is useful to override the
       defaults, to specify non-default built-in tools, and to supply added
       tools:

           env = Environment(tools=['msvc', 'lex'])

       Tools can also be directly called by using the Tool method (see below).

       The tools argument overrides the default tool list, it does not add to
       it, so be sure to include all the tools you need. For example if you
       are building a c/c++ program you must specify a tool for at least a
       compiler and a linker, as in tools=['clang', 'link']. The tool name
       'default' can be used to retain the default list.

       If no tools argument is specified, or if tools includes 'default', then
       scons will auto-detect usable tools, using the execution environment
       value of PATH (that is, env['ENV']['PATH'] - the external evironment
       PATH from os.environ is not used) for looking up any backing programs,
       and the platform name in effect to determine the default tools for that
       platform. Changing the PATH variable after the construction environment
       is constructed will not cause the tools to be re-detected.

       Additional tools can be added to a project either by placing them in a
       site_tools subdirectory of a site directory, or in a custom location
       specified to scons by giving the toolpath keyword argument.  toolpath
       also takes a list as its value:

           env = Environment(tools=['default', 'foo'], toolpath=['tools'])

       This looks for a tool specification module foo.py in directory tools
       and in the standard locations, as well as using the ordinary default
       tools for the platform.

       Directories specified via toolpath are prepended to the existing tool
       path. The default tool path is any site_tools directories, so tools in
       a specified toolpath take priority, followed by tools in a site_tools
       directory, followed by built-in tools. For example, adding a tool
       specification module gcc.py to the toolpath directory would override
       the built-in gcc tool. The tool path is stored in the environment and
       will be used by subsequent calls to the Tool method, as well as by
       env.Clone.

           base = Environment(toolpath=['custom_path'])
           derived = base.Clone(tools=['custom_tool'])
           derived.CustomBuilder()

       A tool specification module must include two functions:

       generate(env, **kwargs)
           Modifies the environment referenced by env to set up variables so
           that the facilities represented by the tool can be executed. It may
           use any keyword arguments that the user supplies in kwargs to vary
           its initialization.

       exists(env)
           Return True if the tool can be called in the context of env.
           Usually this means looking up one or more known programs using the
           PATH from the supplied env, but the tool can make the "exists"
           decision in any way it chooses.

           Note
           At the moment, user-added tools do not automatically have their
           exists function called. As a result, it is recommended that the
           generate function be defensively coded - that is, do not rely on
           any necessary existence checks already having been performed. This
           is expected to be a temporary limitation, and the exists function
           should still be provided.

       The elements of the tools list may also be functions or callable
       objects, in which case the Environment method will call those objects
       to update the new construction environment (see Tool for more details):

           def my_tool(env):
               env['XYZZY'] = 'xyzzy'

           env = Environment(tools=[my_tool])

       The individual elements of the tools list may also themselves be lists
       or tuples of the form (toolname, kw_dict). SCons searches for the
       toolname specification file as described above, and passes kw_dict,
       which must be a dictionary, as keyword arguments to the tool's generate
       function. The generate function can use the arguments to modify the
       tool's behavior by setting up the environment in different ways or
       otherwise changing its initialization.

           # in tools/my_tool.py:
           def generate(env, **kwargs):
             # Sets MY_TOOL to the value of keyword 'arg1' '1' if not supplied
             env['MY_TOOL'] = kwargs.get('arg1', '1')

           def exists(env):
             return True

           # in SConstruct:
           env = Environment(tools=['default', ('my_tool', {'arg1': 'abc'})],
                             toolpath=['tools'])

       The tool specification (my_tool in the example) can use the PLATFORM
       variable from the construction environment it is passed to customize
       the tool for different platforms.

       Tools can be "nested" - that is, they can be located within a
       subdirectory in the toolpath. A nested tool name uses a dot to
       represent a directory separator

           # namespaced builder
           env = Environment(ENV=os.environ.copy(), tools=['SubDir1.SubDir2.SomeTool'])
           env.SomeTool(targets, sources)

           # Search Paths
           # SCons\Tool\SubDir1\SubDir2\SomeTool.py
           # SCons\Tool\SubDir1\SubDir2\SomeTool\__init__.py
           # .\site_scons\site_tools\SubDir1\SubDir2\SomeTool.py
           # .\site_scons\site_tools\SubDir1\SubDir2\SomeTool\__init__.py

       SCons supports the following tool specifications out of the box:

       386asm
           Sets construction variables for the 386ASM assembler for the Phar
           Lap ETS embedded operating system.

           Sets: $AS, $ASCOM, $ASFLAGS, $ASPPCOM, $ASPPFLAGS.

           Uses: $CC, $CPPFLAGS, $_CPPDEFFLAGS, $_CPPINCFLAGS.

       aixc++
           Sets construction variables for the IMB xlc / Visual Age C++
           compiler.

           Sets: $CXX, $CXXVERSION, $SHCXX, $SHOBJSUFFIX.

       aixcc
           Sets construction variables for the IBM xlc / Visual Age C
           compiler.

           Sets: $CC, $CCVERSION, $SHCC.

       aixf77
           Sets construction variables for the IBM Visual Age f77 Fortran
           compiler.

           Sets: $F77, $SHF77.

       aixlink
           Sets construction variables for the IBM Visual Age linker.

           Sets: $LINKFLAGS, $SHLIBSUFFIX, $SHLINKFLAGS.

       applelink
           Sets construction variables for the Apple linker (similar to the
           GNU linker).

           Sets: $APPLELINK_COMPATIBILITY_VERSION, $APPLELINK_CURRENT_VERSION,
           $APPLELINK_NO_COMPATIBILITY_VERSION, $APPLELINK_NO_CURRENT_VERSION,
           $FRAMEWORKPATHPREFIX, $LDMODULECOM, $LDMODULEFLAGS,
           $LDMODULEPREFIX, $LDMODULESUFFIX, $LINKCOM, $SHLINKCOM,
           $SHLINKFLAGS, $_APPLELINK_COMPATIBILITY_VERSION,
           $_APPLELINK_CURRENT_VERSION, $_FRAMEWORKPATH, $_FRAMEWORKS.

           Uses: $FRAMEWORKSFLAGS.

       ar
           Sets construction variables for the ar library archiver.

           Sets: $AR, $ARCOM, $ARFLAGS, $LIBPREFIX, $LIBSUFFIX, $RANLIB,
           $RANLIBCOM, $RANLIBFLAGS.

       as
           Sets construction variables for the as assembler.

           Sets: $AS, $ASCOM, $ASFLAGS, $ASPPCOM, $ASPPFLAGS.

           Uses: $CC, $CPPFLAGS, $_CPPDEFFLAGS, $_CPPINCFLAGS.

       bcc32
           Sets construction variables for the bcc32 compiler.

           Sets: $CC, $CCCOM, $CCFLAGS, $CFILESUFFIX, $CFLAGS, $CPPDEFPREFIX,
           $CPPDEFSUFFIX, $INCPREFIX, $INCSUFFIX, $SHCC, $SHCCCOM, $SHCCFLAGS,
           $SHCFLAGS, $SHOBJSUFFIX.

           Uses: $_CPPDEFFLAGS, $_CPPINCFLAGS.

       cc
           Sets construction variables for generic POSIX C compilers.

           Sets: $CC, $CCCOM, $CCFLAGS, $CFILESUFFIX, $CFLAGS, $CPPDEFPREFIX,
           $CPPDEFSUFFIX, $FRAMEWORKPATH, $FRAMEWORKS, $INCPREFIX, $INCSUFFIX,
           $SHCC, $SHCCCOM, $SHCCFLAGS, $SHCFLAGS, $SHOBJSUFFIX.

           Uses: $CCCOMSTR, $PLATFORM, $SHCCCOMSTR.

       clang
           Set construction variables for the Clang C compiler.

           Sets: $CC, $CCVERSION, $SHCCFLAGS.

       clangxx
           Set construction variables for the Clang C++ compiler.

           Sets: $CXX, $CXXVERSION, $SHCXXFLAGS, $SHOBJSUFFIX,
           $STATIC_AND_SHARED_OBJECTS_ARE_THE_SAME.

       compilation_db
           Sets up CompilationDatabase builder which generates a clang tooling
           compatible compilation database.

           Sets: $COMPILATIONDB_COMSTR, $COMPILATIONDB_PATH_FILTER,
           $COMPILATIONDB_USE_ABSPATH.

       cvf
           Sets construction variables for the Compaq Visual Fortran compiler.

           Sets: $FORTRAN, $FORTRANCOM, $FORTRANMODDIR, $FORTRANMODDIRPREFIX,
           $FORTRANMODDIRSUFFIX, $FORTRANPPCOM, $OBJSUFFIX, $SHFORTRANCOM,
           $SHFORTRANPPCOM.

           Uses: $CPPFLAGS, $FORTRANFLAGS, $SHFORTRANFLAGS, $_CPPDEFFLAGS,
           $_FORTRANINCFLAGS, $_FORTRANMODFLAG.

       cXX
           Sets construction variables for generic POSIX C++ compilers.

           Sets: $CPPDEFPREFIX, $CPPDEFSUFFIX, $CXX, $CXXCOM, $CXXFILESUFFIX,
           $CXXFLAGS, $INCPREFIX, $INCSUFFIX, $OBJSUFFIX, $SHCXX, $SHCXXCOM,
           $SHCXXFLAGS, $SHOBJSUFFIX.

           Uses: $CXXCOMSTR, $SHCXXCOMSTR.

       cyglink
           Set construction variables for cygwin linker/loader.

           Sets: $IMPLIBPREFIX, $IMPLIBSUFFIX, $LDMODULEVERSIONFLAGS,
           $LINKFLAGS, $RPATHPREFIX, $RPATHSUFFIX, $SHLIBPREFIX, $SHLIBSUFFIX,
           $SHLIBVERSIONFLAGS, $SHLINKCOM, $SHLINKFLAGS,
           $_LDMODULEVERSIONFLAGS, $_SHLIBVERSIONFLAGS.

       default
           Sets construction variables for a default list of Tool modules. Use
           default in the tools list to retain the original defaults, since
           the tools parameter is treated as a literal statement of the tools
           to be made available in that construction environment, not an
           addition.

           The list of tools selected by default is not static, but is
           dependent both on the platform and on the software installed on the
           platform. Some tools will not initialize if an underlying command
           is not found, and some tools are selected from a list of choices on
           a first-found basis. The finished tool list can be examined by
           inspecting the $TOOLS construction variable in the construction
           environment.

           On all platforms, the tools from the following list are selected if
           their respective conditions are met: filesystem;, wix, lex, yacc,
           rpcgen, swig, jar, javac, javah, rmic, dvipdf, dvips, gs, tex,
           latex, pdflatex, pdftex, tar, zip, textfile.

           On Linux systems, the default tools list selects (first-found): a C
           compiler from gcc, intelc, icc, cc; a C++ compiler from g++,
           intelc, icc, cXX; an assembler from gas, nasm, masm; a linker from
           gnulink, ilink; a Fortran compiler from gfortran, g77, ifort, ifl,
           f95, f90, f77; and a static archiver ar. It also selects all found
           from the list m4 rpm.

           On Windows systems, the default tools list selects (first-found): a
           C compiler from msvc, mingw, gcc, intelc, icl, icc, cc, bcc32; a
           C++ compiler from msvc, intelc, icc, g++, cXX, bcc32; an assembler
           from masm, nasm, gas, 386asm; a linker from mslink, gnulink, ilink,
           linkloc, ilink32; a Fortran compiler from gfortran, g77, ifl, cvf,
           f95, f90, fortran; and a static archiver from mslib, ar, tlib; It
           also selects all found from the list msvs, midl.

           On MacOS systems, the default tools list selects (first-found): a C
           compiler from gcc, cc; a C++ compiler from g++, cXX; an assembler
           as; a linker from applelink, gnulink; a Fortran compiler from
           gfortran, f95, f90, g77; and a static archiver ar. It also selects
           all found from the list m4, rpm.

           Default lists for other platforms can be found by examining the
           scons source code (see SCons/Tool/__init__.py).

       dmd
           Sets construction variables for D language compiler DMD.

           Sets: $DC, $DCOM, $DDEBUG, $DDEBUGPREFIX, $DDEBUGSUFFIX,
           $DFILESUFFIX, $DFLAGPREFIX, $DFLAGS, $DFLAGSUFFIX, $DINCPREFIX,
           $DINCSUFFIX, $DLIB, $DLIBCOM, $DLIBDIRPREFIX, $DLIBDIRSUFFIX,
           $DLIBFLAGPREFIX, $DLIBFLAGSUFFIX, $DLIBLINKPREFIX, $DLIBLINKSUFFIX,
           $DLINK, $DLINKCOM, $DLINKFLAGPREFIX, $DLINKFLAGS, $DLINKFLAGSUFFIX,
           $DPATH, $DRPATHPREFIX, $DRPATHSUFFIX, $DVERPREFIX, $DVERSIONS,
           $DVERSUFFIX, $SHDC, $SHDCOM, $SHDLIBVERSIONFLAGS, $SHDLINK,
           $SHDLINKCOM, $SHDLINKFLAGS.

       docbook
           This tool tries to make working with Docbook in SCons a little
           easier. It provides several toolchains for creating different
           output formats, like HTML or PDF. Contained in the package is a
           distribution of the Docbook XSL stylesheets as of version 1.76.1.
           As long as you don't specify your own stylesheets for
           customization, these official versions are picked as
           default...which should reduce the inevitable setup hassles for you.

           Implicit dependencies to images and XIncludes are detected
           automatically if you meet the HTML requirements. The additional
           stylesheet utils/xmldepend.xsl by Paul DuBois is used for this
           purpose.

           Note, that there is no support for XML catalog resolving offered!
           This tool calls the XSLT processors and PDF renderers with the
           stylesheets you specified, that's it. The rest lies in your hands
           and you still have to know what you're doing when resolving names
           via a catalog.

           For activating the tool "docbook", you have to add its name to the
           Environment constructor, like this

               env = Environment(tools=['docbook'])

           On its startup, the docbook tool tries to find a required xsltproc
           processor, and a PDF renderer, e.g.  fop. So make sure that these
           are added to your system's environment PATH and can be called
           directly without specifying their full path.

           For the most basic processing of Docbook to HTML, you need to have
           installed

           o   the Python lxml binding to libxml2, or

           o   a standalone XSLT processor, currently detected are xsltproc,
               saxon, saxon-xslt and xalan.

           Rendering to PDF requires you to have one of the applications fop
           or xep installed.

           Creating a HTML or PDF document is very simple and straightforward.
           Say

               env = Environment(tools=['docbook'])
               env.DocbookHtml('manual.html', 'manual.xml')
               env.DocbookPdf('manual.pdf', 'manual.xml')

           to get both outputs from your XML source manual.xml. As a shortcut,
           you can give the stem of the filenames alone, like this:

               env = Environment(tools=['docbook'])
               env.DocbookHtml('manual')
               env.DocbookPdf('manual')

           and get the same result. Target and source lists are also
           supported:

               env = Environment(tools=['docbook'])
               env.DocbookHtml(['manual.html','reference.html'], ['manual.xml','reference.xml'])

           or even

               env = Environment(tools=['docbook'])
               env.DocbookHtml(['manual','reference'])


               Important
               Whenever you leave out the list of sources, you may not specify
               a file extension! The Tool uses the given names as file stems,
               and adds the suffixes for target and source files accordingly.
           The rules given above are valid for the Builders DocbookHtml,
           DocbookPdf, DocbookEpub, DocbookSlidesPdf and DocbookXInclude. For
           the DocbookMan transformation you can specify a target name, but
           the actual output names are automatically set from the refname
           entries in your XML source.

           The Builders DocbookHtmlChunked, DocbookHtmlhelp and
           DocbookSlidesHtml are special, in that:

            1. they create a large set of files, where the exact names and
               their number depend on the content of the source file, and

            2. the main target is always named index.html, i.e. the output
               name for the XSL transformation is not picked up by the
               stylesheets.

           As a result, there is simply no use in specifying a target HTML
           name. So the basic syntax for these builders is always:

               env = Environment(tools=['docbook'])
               env.DocbookHtmlhelp('manual')

           If you want to use a specific XSL file, you can set the additional
           xsl parameter to your Builder call as follows:

               env.DocbookHtml('other.html', 'manual.xml', xsl='html.xsl')

           Since this may get tedious if you always use the same local naming
           for your customized XSL files, e.g.  html.xsl for HTML and pdf.xsl
           for PDF output, a set of variables for setting the default XSL name
           is provided. These are:

               DOCBOOK_DEFAULT_XSL_HTML
               DOCBOOK_DEFAULT_XSL_HTMLCHUNKED
               DOCBOOK_DEFAULT_XSL_HTMLHELP
               DOCBOOK_DEFAULT_XSL_PDF
               DOCBOOK_DEFAULT_XSL_EPUB
               DOCBOOK_DEFAULT_XSL_MAN
               DOCBOOK_DEFAULT_XSL_SLIDESPDF
               DOCBOOK_DEFAULT_XSL_SLIDESHTML

           and you can set them when constructing your environment:

               env = Environment(
                   tools=['docbook'],
                   DOCBOOK_DEFAULT_XSL_HTML='html.xsl',
                   DOCBOOK_DEFAULT_XSL_PDF='pdf.xsl',
               )
               env.DocbookHtml('manual')  # now uses html.xsl

           Sets: $DOCBOOK_DEFAULT_XSL_EPUB, $DOCBOOK_DEFAULT_XSL_HTML,
           $DOCBOOK_DEFAULT_XSL_HTMLCHUNKED, $DOCBOOK_DEFAULT_XSL_HTMLHELP,
           $DOCBOOK_DEFAULT_XSL_MAN, $DOCBOOK_DEFAULT_XSL_PDF,
           $DOCBOOK_DEFAULT_XSL_SLIDESHTML, $DOCBOOK_DEFAULT_XSL_SLIDESPDF,
           $DOCBOOK_FOP, $DOCBOOK_FOPCOM, $DOCBOOK_FOPFLAGS, $DOCBOOK_XMLLINT,
           $DOCBOOK_XMLLINTCOM, $DOCBOOK_XMLLINTFLAGS, $DOCBOOK_XSLTPROC,
           $DOCBOOK_XSLTPROCCOM, $DOCBOOK_XSLTPROCFLAGS,
           $DOCBOOK_XSLTPROCPARAMS.

           Uses: $DOCBOOK_FOPCOMSTR, $DOCBOOK_XMLLINTCOMSTR,
           $DOCBOOK_XSLTPROCCOMSTR.

       dvi
           Attaches the DVI builder to the construction environment.

       dvipdf
           Sets construction variables for the dvipdf utility.

           Sets: $DVIPDF, $DVIPDFCOM, $DVIPDFFLAGS.

           Uses: $DVIPDFCOMSTR.

       dvips
           Sets construction variables for the dvips utility.

           Sets: $DVIPS, $DVIPSFLAGS, $PSCOM, $PSPREFIX, $PSSUFFIX.

           Uses: $PSCOMSTR.

       f03
           Set construction variables for generic POSIX Fortran 03 compilers.

           Sets: $F03, $F03COM, $F03FLAGS, $F03PPCOM, $SHF03, $SHF03COM,
           $SHF03FLAGS, $SHF03PPCOM, $_F03INCFLAGS.

           Uses: $F03COMSTR, $F03PPCOMSTR, $SHF03COMSTR, $SHF03PPCOMSTR.

       f08
           Set construction variables for generic POSIX Fortran 08 compilers.

           Sets: $F08, $F08COM, $F08FLAGS, $F08PPCOM, $SHF08, $SHF08COM,
           $SHF08FLAGS, $SHF08PPCOM, $_F08INCFLAGS.

           Uses: $F08COMSTR, $F08PPCOMSTR, $SHF08COMSTR, $SHF08PPCOMSTR.

       f77
           Set construction variables for generic POSIX Fortran 77 compilers.

           Sets: $F77, $F77COM, $F77FILESUFFIXES, $F77FLAGS, $F77PPCOM,
           $F77PPFILESUFFIXES, $FORTRAN, $FORTRANCOM, $FORTRANFLAGS, $SHF77,
           $SHF77COM, $SHF77FLAGS, $SHF77PPCOM, $SHFORTRAN, $SHFORTRANCOM,
           $SHFORTRANFLAGS, $SHFORTRANPPCOM, $_F77INCFLAGS.

           Uses: $F77COMSTR, $F77PPCOMSTR, $FORTRANCOMSTR, $FORTRANPPCOMSTR,
           $SHF77COMSTR, $SHF77PPCOMSTR, $SHFORTRANCOMSTR, $SHFORTRANPPCOMSTR.

       f90
           Set construction variables for generic POSIX Fortran 90 compilers.

           Sets: $F90, $F90COM, $F90FLAGS, $F90PPCOM, $SHF90, $SHF90COM,
           $SHF90FLAGS, $SHF90PPCOM, $_F90INCFLAGS.

           Uses: $F90COMSTR, $F90PPCOMSTR, $SHF90COMSTR, $SHF90PPCOMSTR.

       f95
           Set construction variables for generic POSIX Fortran 95 compilers.

           Sets: $F95, $F95COM, $F95FLAGS, $F95PPCOM, $SHF95, $SHF95COM,
           $SHF95FLAGS, $SHF95PPCOM, $_F95INCFLAGS.

           Uses: $F95COMSTR, $F95PPCOMSTR, $SHF95COMSTR, $SHF95PPCOMSTR.

       fortran
           Set construction variables for generic POSIX Fortran compilers.

           Sets: $FORTRAN, $FORTRANCOM, $FORTRANFLAGS, $SHFORTRAN,
           $SHFORTRANCOM, $SHFORTRANFLAGS, $SHFORTRANPPCOM.

           Uses: $FORTRANCOMSTR, $FORTRANPPCOMSTR, $SHFORTRANCOMSTR,
           $SHFORTRANPPCOMSTR.

       g++
           Set construction variables for the g++ C++ compiler.

           Sets: $CXX, $CXXVERSION, $SHCXXFLAGS, $SHOBJSUFFIX.

       g77
           Set construction variables for the g77 Fortran compiler. Calls the
           f77 Tool module to set variables.

       gas
           Sets construction variables for the gas assembler. Calls the as
           tool.

           Sets: $AS.

       gcc
           Set construction variables for the gcc C compiler.

           Sets: $CC, $CCVERSION, $SHCCFLAGS.

       gdc
           Sets construction variables for the D language compiler GDC.

           Sets: $DC, $DCOM, $DDEBUG, $DDEBUGPREFIX, $DDEBUGSUFFIX,
           $DFILESUFFIX, $DFLAGPREFIX, $DFLAGS, $DFLAGSUFFIX, $DINCPREFIX,
           $DINCSUFFIX, $DLIB, $DLIBCOM, $DLIBDIRPREFIX, $DLIBDIRSUFFIX,
           $DLIBFLAGPREFIX, $DLIBFLAGSUFFIX, $DLIBLINKPREFIX, $DLIBLINKSUFFIX,
           $DLINK, $DLINKCOM, $DLINKFLAGPREFIX, $DLINKFLAGS, $DLINKFLAGSUFFIX,
           $DPATH, $DRPATHPREFIX, $DRPATHSUFFIX, $DVERPREFIX, $DVERSIONS,
           $DVERSUFFIX, $SHDC, $SHDCOM, $SHDLIBVERSIONFLAGS, $SHDLINK,
           $SHDLINKCOM, $SHDLINKFLAGS.

       gettext
           This is actually a toolset, which supports internationalization and
           localization of software being constructed with SCons. The toolset
           loads following tools:



           o    xgettext - to extract internationalized messages from source
               code to POT file(s),

           o    msginit - may be optionally used to initialize PO files,

           o    msgmerge - to update PO files, that already contain translated
               messages,

           o    msgfmt - to compile textual PO file to binary installable MO
               file.

           When you enable gettext, it internally loads all abovementioned
           tools, so you're encouraged to see their individual documentation.

           Each of the above tools provides its own builder(s) which may be
           used to perform particular activities related to software
           internationalization. You may be however interested in top-level
           Translate builder.

           To use gettext tools add 'gettext' tool to your environment:

                 env = Environment( tools = ['default', 'gettext'] )

       gfortran
           Sets construction variables for the GNU F95/F2003 GNU compiler.

           Sets: $F77, $F90, $F95, $FORTRAN, $SHF77, $SHF77FLAGS, $SHF90,
           $SHF90FLAGS, $SHF95, $SHF95FLAGS, $SHFORTRAN, $SHFORTRANFLAGS.

       gnulink
           Set construction variables for GNU linker/loader.

           Sets: $LDMODULEVERSIONFLAGS, $RPATHPREFIX, $RPATHSUFFIX,
           $SHLIBVERSIONFLAGS, $SHLINKFLAGS, $_LDMODULESONAME, $_SHLIBSONAME.

       gs
           This Tool sets the required construction variables for working with
           the Ghostscript software. It also registers an appropriate Action
           with the PDF Builder, such that the conversion from PS/EPS to PDF
           happens automatically for the TeX/LaTeX toolchain. Finally, it adds
           an explicit Gs Builder for Ghostscript to the environment.

           Sets: $GS, $GSCOM, $GSFLAGS.

           Uses: $GSCOMSTR.

       hpc++
           Set construction variables for the compilers aCC on HP/UX systems.

       hpcc
           Set construction variables for aCC compilers on HP/UX systems.
           Calls the cXX tool for additional variables.

           Sets: $CXX, $CXXVERSION, $SHCXXFLAGS.

       hplink
           Sets construction variables for the linker on HP/UX systems.

           Sets: $LINKFLAGS, $SHLIBSUFFIX, $SHLINKFLAGS.

       icc
           Sets construction variables for the icc compiler on OS/2 systems.

           Sets: $CC, $CCCOM, $CFILESUFFIX, $CPPDEFPREFIX, $CPPDEFSUFFIX,
           $CXXCOM, $CXXFILESUFFIX, $INCPREFIX, $INCSUFFIX.

           Uses: $CCFLAGS, $CFLAGS, $CPPFLAGS, $_CPPDEFFLAGS, $_CPPINCFLAGS.

       icl
           Sets construction variables for the Intel C/C++ compiler. Calls the
           intelc Tool module to set its variables.

       ifl
           Sets construction variables for the Intel Fortran compiler.

           Sets: $FORTRAN, $FORTRANCOM, $FORTRANPPCOM, $SHFORTRANCOM,
           $SHFORTRANPPCOM.

           Uses: $CPPFLAGS, $FORTRANFLAGS, $_CPPDEFFLAGS, $_FORTRANINCFLAGS.

       ifort
           Sets construction variables for newer versions of the Intel Fortran
           compiler for Linux.

           Sets: $F77, $F90, $F95, $FORTRAN, $SHF77, $SHF77FLAGS, $SHF90,
           $SHF90FLAGS, $SHF95, $SHF95FLAGS, $SHFORTRAN, $SHFORTRANFLAGS.

       ilink
           Sets construction variables for the ilink linker on OS/2 systems.

           Sets: $LIBDIRPREFIX, $LIBDIRSUFFIX, $LIBLINKPREFIX, $LIBLINKSUFFIX,
           $LINK, $LINKCOM, $LINKFLAGS.

       ilink32
           Sets construction variables for the Borland ilink32 linker.

           Sets: $LIBDIRPREFIX, $LIBDIRSUFFIX, $LIBLINKPREFIX, $LIBLINKSUFFIX,
           $LINK, $LINKCOM, $LINKFLAGS.

       install
           Sets construction variables for file and directory installation.

           Sets: $INSTALL, $INSTALLSTR.

       intelc
           Sets construction variables for the Intel C/C++ compiler (Linux and
           Windows, version 7 and later). Calls the gcc or msvc (on Linux and
           Windows, respectively) tool to set underlying variables.

           Sets: $AR, $CC, $CXX, $INTEL_C_COMPILER_VERSION, $LINK.

       jar
           Sets construction variables for the jar utility.

           Sets: $JAR, $JARCOM, $JARFLAGS, $JARSUFFIX.

           Uses: $JARCOMSTR.

       javac
           Sets construction variables for the javac compiler.

           Sets: $JAVABOOTCLASSPATH, $JAVAC, $JAVACCOM, $JAVACFLAGS,
           $JAVACLASSPATH, $JAVACLASSSUFFIX, $JAVAINCLUDES, $JAVASOURCEPATH,
           $JAVASUFFIX.

           Uses: $JAVACCOMSTR.

       javah
           Sets construction variables for the javah tool.

           Sets: $JAVACLASSSUFFIX, $JAVAH, $JAVAHCOM, $JAVAHFLAGS.

           Uses: $JAVACLASSPATH, $JAVAHCOMSTR.

       latex
           Sets construction variables for the latex utility.

           Sets: $LATEX, $LATEXCOM, $LATEXFLAGS.

           Uses: $LATEXCOMSTR.

       ldc
           Sets construction variables for the D language compiler LDC2.

           Sets: $DC, $DCOM, $DDEBUG, $DDEBUGPREFIX, $DDEBUGSUFFIX,
           $DFILESUFFIX, $DFLAGPREFIX, $DFLAGS, $DFLAGSUFFIX, $DINCPREFIX,
           $DINCSUFFIX, $DLIB, $DLIBCOM, $DLIBDIRPREFIX, $DLIBDIRSUFFIX,
           $DLIBFLAGPREFIX, $DLIBFLAGSUFFIX, $DLIBLINKPREFIX, $DLIBLINKSUFFIX,
           $DLINK, $DLINKCOM, $DLINKFLAGPREFIX, $DLINKFLAGS, $DLINKFLAGSUFFIX,
           $DPATH, $DRPATHPREFIX, $DRPATHSUFFIX, $DVERPREFIX, $DVERSIONS,
           $DVERSUFFIX, $SHDC, $SHDCOM, $SHDLIBVERSIONFLAGS, $SHDLINK,
           $SHDLINKCOM, $SHDLINKFLAGS.

       lex
           Sets construction variables for the lex lexical analyser.

           Sets: $LEX, $LEXCOM, $LEXFLAGS, $LEXUNISTD.

           Uses: $LEXCOMSTR.

       link
           Sets construction variables for generic POSIX linkers. This is a
           "smart" linker tool which selects a compiler to complete the
           linking based on the types of source files.

           Sets: $LDMODULE, $LDMODULECOM, $LDMODULEFLAGS,
           $LDMODULENOVERSIONSYMLINKS, $LDMODULEPREFIX, $LDMODULESUFFIX,
           $LDMODULEVERSION, $LDMODULEVERSIONFLAGS, $LIBDIRPREFIX,
           $LIBDIRSUFFIX, $LIBLINKPREFIX, $LIBLINKSUFFIX, $LINK, $LINKCOM,
           $LINKFLAGS, $SHLIBSUFFIX, $SHLINK, $SHLINKCOM, $SHLINKFLAGS,
           $__LDMODULEVERSIONFLAGS, $__SHLIBVERSIONFLAGS.

           Uses: $LDMODULECOMSTR, $LINKCOMSTR, $SHLINKCOMSTR.

       linkloc
           Sets construction variables for the LinkLoc linker for the Phar Lap
           ETS embedded operating system.

           Sets: $LIBDIRPREFIX, $LIBDIRSUFFIX, $LIBLINKPREFIX, $LIBLINKSUFFIX,
           $LINK, $LINKCOM, $LINKFLAGS, $SHLINK, $SHLINKCOM, $SHLINKFLAGS.

           Uses: $LINKCOMSTR, $SHLINKCOMSTR.

       m4
           Sets construction variables for the m4 macro processor.

           Sets: $M4, $M4COM, $M4FLAGS.

           Uses: $M4COMSTR.

       masm
           Sets construction variables for the Microsoft assembler.

           Sets: $AS, $ASCOM, $ASFLAGS, $ASPPCOM, $ASPPFLAGS.

           Uses: $ASCOMSTR, $ASPPCOMSTR, $CPPFLAGS, $_CPPDEFFLAGS,
           $_CPPINCFLAGS.

       midl
           Sets construction variables for the Microsoft IDL compiler.

           Sets: $MIDL, $MIDLCOM, $MIDLFLAGS.

           Uses: $MIDLCOMSTR.

       mingw
           Sets construction variables for MinGW (Minimal Gnu on Windows).

           Sets: $AS, $CC, $CXX, $LDMODULECOM, $LIBPREFIX, $LIBSUFFIX,
           $OBJSUFFIX, $RC, $RCCOM, $RCFLAGS, $RCINCFLAGS, $RCINCPREFIX,
           $RCINCSUFFIX, $SHCCFLAGS, $SHCXXFLAGS, $SHLINKCOM, $SHLINKFLAGS,
           $SHOBJSUFFIX, $WINDOWSDEFPREFIX, $WINDOWSDEFSUFFIX.

           Uses: $RCCOMSTR, $SHLINKCOMSTR.

       msgfmt
           This scons tool is a part of scons gettext toolset. It provides
           scons interface to msgfmt(1) command, which generates binary
           message catalog (MO) from a textual translation description (PO).

           Sets: $MOSUFFIX, $MSGFMT, $MSGFMTCOM, $MSGFMTCOMSTR, $MSGFMTFLAGS,
           $POSUFFIX.

           Uses: $LINGUAS_FILE.

       msginit
           This scons tool is a part of scons gettext toolset. It provides
           scons interface to msginit(1) program, which creates new PO file,
           initializing the meta information with values from user's
           environment (or options).

           Sets: $MSGINIT, $MSGINITCOM, $MSGINITCOMSTR, $MSGINITFLAGS,
           $POAUTOINIT, $POCREATE_ALIAS, $POSUFFIX, $POTSUFFIX,
           $_MSGINITLOCALE.

           Uses: $LINGUAS_FILE, $POAUTOINIT, $POTDOMAIN.

       msgmerge
           This scons tool is a part of scons gettext toolset. It provides
           scons interface to msgmerge(1) command, which merges two Uniform
           style .po files together.

           Sets: $MSGMERGE, $MSGMERGECOM, $MSGMERGECOMSTR, $MSGMERGEFLAGS,
           $POSUFFIX, $POTSUFFIX, $POUPDATE_ALIAS.

           Uses: $LINGUAS_FILE, $POAUTOINIT, $POTDOMAIN.

       mslib
           Sets construction variables for the Microsoft mslib library
           archiver.

           Sets: $AR, $ARCOM, $ARFLAGS, $LIBPREFIX, $LIBSUFFIX.

           Uses: $ARCOMSTR.

       mslink
           Sets construction variables for the Microsoft linker.

           Sets: $LDMODULE, $LDMODULECOM, $LDMODULEFLAGS, $LDMODULEPREFIX,
           $LDMODULESUFFIX, $LIBDIRPREFIX, $LIBDIRSUFFIX, $LIBLINKPREFIX,
           $LIBLINKSUFFIX, $LINK, $LINKCOM, $LINKFLAGS, $REGSVR, $REGSVRCOM,
           $REGSVRFLAGS, $SHLINK, $SHLINKCOM, $SHLINKFLAGS, $WINDOWSDEFPREFIX,
           $WINDOWSDEFSUFFIX, $WINDOWSEXPPREFIX, $WINDOWSEXPSUFFIX,
           $WINDOWSPROGMANIFESTPREFIX, $WINDOWSPROGMANIFESTSUFFIX,
           $WINDOWSSHLIBMANIFESTPREFIX, $WINDOWSSHLIBMANIFESTSUFFIX,
           $WINDOWS_INSERT_DEF.

           Uses: $LDMODULECOMSTR, $LINKCOMSTR, $REGSVRCOMSTR, $SHLINKCOMSTR.

       mssdk
           Sets variables for Microsoft Platform SDK and/or Windows SDK. Note
           that unlike most other Tool modules, mssdk does not set
           construction variables, but sets the environment variables in the
           environment SCons uses to execute the Microsoft toolchain:
           %INCLUDE%, %LIB%, %LIBPATH% and %PATH%.

           Uses: $MSSDK_DIR, $MSSDK_VERSION, $MSVS_VERSION.

       msvc
           Sets construction variables for the Microsoft Visual C/C++
           compiler.

           Sets: $BUILDERS, $CC, $CCCOM, $CCFLAGS, $CCPCHFLAGS, $CCPDBFLAGS,
           $CFILESUFFIX, $CFLAGS, $CPPDEFPREFIX, $CPPDEFSUFFIX, $CXX, $CXXCOM,
           $CXXFILESUFFIX, $CXXFLAGS, $INCPREFIX, $INCSUFFIX, $OBJPREFIX,
           $OBJSUFFIX, $PCHCOM, $PCHPDBFLAGS, $RC, $RCCOM, $RCFLAGS, $SHCC,
           $SHCCCOM, $SHCCFLAGS, $SHCFLAGS, $SHCXX, $SHCXXCOM, $SHCXXFLAGS,
           $SHOBJPREFIX, $SHOBJSUFFIX.

           Uses: $CCCOMSTR, $CXXCOMSTR, $PCH, $PCHSTOP, $PDB, $SHCCCOMSTR,
           $SHCXXCOMSTR.

       msvs
           Sets construction variables for Microsoft Visual Studio.

           Sets: $MSVSBUILDCOM, $MSVSCLEANCOM, $MSVSENCODING, $MSVSPROJECTCOM,
           $MSVSREBUILDCOM, $MSVSSCONS, $MSVSSCONSCOM, $MSVSSCONSCRIPT,
           $MSVSSCONSFLAGS, $MSVSSOLUTIONCOM.

       mwcc
           Sets construction variables for the Metrowerks CodeWarrior
           compiler.

           Sets: $CC, $CCCOM, $CFILESUFFIX, $CPPDEFPREFIX, $CPPDEFSUFFIX,
           $CXX, $CXXCOM, $CXXFILESUFFIX, $INCPREFIX, $INCSUFFIX,
           $MWCW_VERSION, $MWCW_VERSIONS, $SHCC, $SHCCCOM, $SHCCFLAGS,
           $SHCFLAGS, $SHCXX, $SHCXXCOM, $SHCXXFLAGS.

           Uses: $CCCOMSTR, $CXXCOMSTR, $SHCCCOMSTR, $SHCXXCOMSTR.

       mwld
           Sets construction variables for the Metrowerks CodeWarrior linker.

           Sets: $AR, $ARCOM, $LIBDIRPREFIX, $LIBDIRSUFFIX, $LIBLINKPREFIX,
           $LIBLINKSUFFIX, $LINK, $LINKCOM, $SHLINK, $SHLINKCOM, $SHLINKFLAGS.

       nasm
           Sets construction variables for the nasm Netwide Assembler.

           Sets: $AS, $ASCOM, $ASFLAGS, $ASPPCOM, $ASPPFLAGS.

           Uses: $ASCOMSTR, $ASPPCOMSTR.

       ninja
           Sets up Ninja builder which generates a ninja build file, and then
           optionally runs ninja.

               Note
               This is an experimental feature.

               This functionality is subject to change and/or removal without
               deprecation cycle.
           Sets: $IMPLICIT_COMMAND_DEPENDENCIES, $NINJA_ALIAS_NAME,
           $NINJA_COMPDB_EXPAND, $NINJA_DIR, $NINJA_DISABLE_AUTO_RUN,
           $NINJA_ENV_VAR_CACHE, $NINJA_FILE_NAME,
           $NINJA_GENERATED_SOURCE_SUFFIXES, $NINJA_MSVC_DEPS_PREFIX,
           $NINJA_POOL, $NINJA_REGENERATE_DEPS, $NINJA_SYNTAX,
           $_NINJA_REGENERATE_DEPS_FUNC, $__NINJA_NO.

           Uses: $AR, $ARCOM, $ARFLAGS, $CC, $CCCOM, $CCFLAGS, $CXX, $CXXCOM,
           $ESCAPE, $LINK, $LINKCOM, $PLATFORM, $PRINT_CMD_LINE_FUNC,
           $PROGSUFFIX, $RANLIB, $RANLIBCOM, $SHCCCOM, $SHCXXCOM, $SHLINK,
           $SHLINKCOM.

       packaging
           Sets construction variables for the Package Builder. If this tool
           is enabled, the --package-type command-line option is also enabled.

       pdf
           Sets construction variables for the Portable Document Format
           builder.

           Sets: $PDFPREFIX, $PDFSUFFIX.

       pdflatex
           Sets construction variables for the pdflatex utility.

           Sets: $LATEXRETRIES, $PDFLATEX, $PDFLATEXCOM, $PDFLATEXFLAGS.

           Uses: $PDFLATEXCOMSTR.

       pdftex
           Sets construction variables for the pdftex utility.

           Sets: $LATEXRETRIES, $PDFLATEX, $PDFLATEXCOM, $PDFLATEXFLAGS,
           $PDFTEX, $PDFTEXCOM, $PDFTEXFLAGS.

           Uses: $PDFLATEXCOMSTR, $PDFTEXCOMSTR.

       python
           Loads the Python source scanner into the invoking environment. When
           loaded, the scanner will attempt to find implicit dependencies for
           any Python source files in the list of sources provided to an
           Action that uses this environment.

           Available since scons 4.0..

       qt
           Sets construction variables for building Qt applications.

           Sets: $QTDIR, $QT_AUTOSCAN, $QT_BINPATH, $QT_CPPPATH, $QT_LIB,
           $QT_LIBPATH, $QT_MOC, $QT_MOCCXXPREFIX, $QT_MOCCXXSUFFIX,
           $QT_MOCFROMCXXCOM, $QT_MOCFROMCXXFLAGS, $QT_MOCFROMHCOM,
           $QT_MOCFROMHFLAGS, $QT_MOCHPREFIX, $QT_MOCHSUFFIX, $QT_UIC,
           $QT_UICCOM, $QT_UICDECLFLAGS, $QT_UICDECLPREFIX, $QT_UICDECLSUFFIX,
           $QT_UICIMPLFLAGS, $QT_UICIMPLPREFIX, $QT_UICIMPLSUFFIX,
           $QT_UISUFFIX.

       rmic
           Sets construction variables for the rmic utility.

           Sets: $JAVACLASSSUFFIX, $RMIC, $RMICCOM, $RMICFLAGS.

           Uses: $RMICCOMSTR.

       rpcgen
           Sets construction variables for building with RPCGEN.

           Sets: $RPCGEN, $RPCGENCLIENTFLAGS, $RPCGENFLAGS,
           $RPCGENHEADERFLAGS, $RPCGENSERVICEFLAGS, $RPCGENXDRFLAGS.

       sgiar
           Sets construction variables for the SGI library archiver.

           Sets: $AR, $ARCOMSTR, $ARFLAGS, $LIBPREFIX, $LIBSUFFIX, $SHLINK,
           $SHLINKFLAGS.

           Uses: $ARCOMSTR, $SHLINKCOMSTR.

       sgic++
           Sets construction variables for the SGI C++ compiler.

           Sets: $CXX, $CXXFLAGS, $SHCXX, $SHOBJSUFFIX.

       sgicc
           Sets construction variables for the SGI C compiler.

           Sets: $CXX, $SHOBJSUFFIX.

       sgilink
           Sets construction variables for the SGI linker.

           Sets: $LINK, $RPATHPREFIX, $RPATHSUFFIX, $SHLINKFLAGS.

       sunar
           Sets construction variables for the Sun library archiver.

           Sets: $AR, $ARCOM, $ARFLAGS, $LIBPREFIX, $LIBSUFFIX.

           Uses: $ARCOMSTR.

       sunc++
           Sets construction variables for the Sun C++ compiler.

           Sets: $CXX, $CXXVERSION, $SHCXX, $SHCXXFLAGS, $SHOBJPREFIX,
           $SHOBJSUFFIX.

       suncc
           Sets construction variables for the Sun C compiler.

           Sets: $CXX, $SHCCFLAGS, $SHOBJPREFIX, $SHOBJSUFFIX.

       sunf77
           Set construction variables for the Sun f77 Fortran compiler.

           Sets: $F77, $FORTRAN, $SHF77, $SHF77FLAGS, $SHFORTRAN,
           $SHFORTRANFLAGS.

       sunf90
           Set construction variables for the Sun f90 Fortran compiler.

           Sets: $F90, $FORTRAN, $SHF90, $SHF90FLAGS, $SHFORTRAN,
           $SHFORTRANFLAGS.

       sunf95
           Set construction variables for the Sun f95 Fortran compiler.

           Sets: $F95, $FORTRAN, $SHF95, $SHF95FLAGS, $SHFORTRAN,
           $SHFORTRANFLAGS.

       sunlink
           Sets construction variables for the Sun linker.

           Sets: $RPATHPREFIX, $RPATHSUFFIX, $SHLINKFLAGS.

       swig
           Sets construction variables for the SWIG interface generator.

           Sets: $SWIG, $SWIGCFILESUFFIX, $SWIGCOM, $SWIGCXXFILESUFFIX,
           $SWIGDIRECTORSUFFIX, $SWIGFLAGS, $SWIGINCPREFIX, $SWIGINCSUFFIX,
           $SWIGPATH, $SWIGVERSION, $_SWIGINCFLAGS.

           Uses: $SWIGCOMSTR.

       tar
           Sets construction variables for the tar archiver.

           Sets: $TAR, $TARCOM, $TARFLAGS, $TARSUFFIX.

           Uses: $TARCOMSTR.

       tex
           Sets construction variables for the TeX formatter and typesetter.

           Sets: $BIBTEX, $BIBTEXCOM, $BIBTEXFLAGS, $LATEX, $LATEXCOM,
           $LATEXFLAGS, $MAKEINDEX, $MAKEINDEXCOM, $MAKEINDEXFLAGS, $TEX,
           $TEXCOM, $TEXFLAGS.

           Uses: $BIBTEXCOMSTR, $LATEXCOMSTR, $MAKEINDEXCOMSTR, $TEXCOMSTR.

       textfile
           Set construction variables for the Textfile and Substfile builders.

           Sets: $LINESEPARATOR, $SUBSTFILEPREFIX, $SUBSTFILESUFFIX,
           $TEXTFILEPREFIX, $TEXTFILESUFFIX.

           Uses: $SUBST_DICT.

       tlib
           Sets construction variables for the Borlan tib library archiver.

           Sets: $AR, $ARCOM, $ARFLAGS, $LIBPREFIX, $LIBSUFFIX.

           Uses: $ARCOMSTR.

       xgettext
           This scons tool is a part of scons gettext toolset. It provides
           scons interface to xgettext(1) program, which extracts
           internationalized messages from source code. The tool provides
           POTUpdate builder to make PO Template files.

           Sets: $POTSUFFIX, $POTUPDATE_ALIAS, $XGETTEXTCOM, $XGETTEXTCOMSTR,
           $XGETTEXTFLAGS, $XGETTEXTFROM, $XGETTEXTFROMPREFIX,
           $XGETTEXTFROMSUFFIX, $XGETTEXTPATH, $XGETTEXTPATHPREFIX,
           $XGETTEXTPATHSUFFIX, $_XGETTEXTDOMAIN, $_XGETTEXTFROMFLAGS,
           $_XGETTEXTPATHFLAGS.

           Uses: $POTDOMAIN.

       yacc
           Sets construction variables for the yacc parse generator.

           Sets: $YACC, $YACCCOM, $YACCFLAGS, $YACCHFILESUFFIX,
           $YACCHXXFILESUFFIX, $YACCVCGFILESUFFIX.

           Uses: $YACCCOMSTR.

       zip
           Sets construction variables for the zip archiver.

           Sets: $ZIP, $ZIPCOM, $ZIPCOMPRESSION, $ZIPFLAGS, $ZIPSUFFIX.

           Uses: $ZIPCOMSTR.

   Builder Methods
       You tell scons what to build by calling Builders, functions which take
       particular action(s) to produce a particular result type
       (conventionally described by the builder name such as Program) when
       given source files of a particular type. Calling a builder defines one
       or more targets to the build system; whether the targets are actually
       built on a given invocation is determined by command-line options,
       target selection rules, and whether SCons determines the target(s) are
       out of date.

       SCons defines a number of builders, and you can also write your own.
       Builders are attached to a construction environment as methods, and the
       available builder methods are listed as key-value pairs in the BUILDERS
       attribute of the construction environment. The available builders can
       be displayed like this for debugging purposes:

           env = Environment()
           print("Builders:", list(env['BUILDERS']))

       Builder methods take two required arguments: target and source. Either
       can be passed as a scalar or as a list. The target and source arguments
       can be specified either as positional arguments, in which case target
       comes first, or as keyword arguments, using target= and source=.
       Although both arguments are nominally required, if there is a single
       source and the target can be inferred the target argument can be
       omitted (see below). Builder methods also take a variety of keyword
       arguments, described below.

       The builder may add other targets beyond those requested if indicated
       by an Emitter (see the section called "Builder Objects" and, for
       example, $PROGEMITTER for more information).

       Because long lists of file names can lead to a lot of quoting, scons
       supplies a Split global function and a same-named environment method
       that splits a single string into a list, using strings of white-space
       characters as the delimiter. (similar to the Python string split
       method, but succeeds even if the input isn't a string.)

       The following are equivalent examples of calling the Program builder
       method:

           env.Program('bar', ['bar.c', 'foo.c'])
           env.Program('bar', Split('bar.c foo.c'))
           env.Program('bar', env.Split('bar.c foo.c'))
           env.Program(source=['bar.c', 'foo.c'], target='bar')
           env.Program(target='bar', source=Split('bar.c foo.c'))
           env.Program(target='bar', source=env.Split('bar.c foo.c'))
           env.Program('bar', source='bar.c foo.c'.split())

       Python follows the POSIX pathname convention for path strings: if a
       string begins with the operating system pathname separator (on Windows
       both the slash and backslash separator work, and any leading drive
       specifier is ignored for the determination) it is considered an
       absolute path, otherwise it is a relative path. If the path string
       contains no separator characters, it is searched for as a file in the
       current directory. If it contains separator characters, the search
       follows down from the starting point, which is the top of the directory
       tree for an absolute path and the current directory for a relative
       path.

       scons recognizes a third way to specify path strings: if the string
       begins with the # character it is top-relative - it works like a
       relative path but the search follows down from the directory containing
       the top-level SConstruct rather than from the current directory. The #
       is allowed to be followed by a pathname separator, which is ignored if
       found in that position. Top-relative paths only work in places where
       scons will interpret the path (see some examples below). To be used in
       other contexts the string will need to be converted to a relative or
       absolute path first.

       target and source can be absolute, relative, or top-relative. Relative
       pathnames are searched considering the directory of the SConscript file
       currently being processed as the "current directory".

       Examples:

           # The comments describing the targets that will be built
           # assume these calls are in a SConscript file in the
           # a subdirectory named "subdir".

           # Builds the program "subdir/foo" from "subdir/foo.c":
           env.Program('foo', 'foo.c')

           # Builds the program "/tmp/bar" from "subdir/bar.c":
           env.Program('/tmp/bar', 'bar.c')

           # An initial '#' or '#/' are equivalent; the following
           # calls build the programs "foo" and "bar" (in the
           # top-level SConstruct directory) from "subdir/foo.c" and
           # "subdir/bar.c", respectively:
           env.Program('#foo', 'foo.c')
           env.Program('#/bar', 'bar.c')

           # Builds the program "other/foo" (relative to the top-level
           # SConstruct directory) from "subdir/foo.c":
           env.Program('#other/foo', 'foo.c')

           # This will not work, only SCons interfaces understand '#',
           # os.path.exists is pure Python:
           if os.path.exists('#inc/foo.h'):
               env.Append(CPPPATH='#inc')

       When the target shares the same base name as the source and only the
       suffix varies, and if the builder method has a suffix defined for the
       target file type, then the target argument may be omitted completely,
       and scons will deduce the target file name from the source file name.
       The following examples all build the executable program bar (on POSIX
       systems) or bar.exe (on Windows systems) from the bar.c source file:

           env.Program(target='bar', source='bar.c')
           env.Program('bar', source='bar.c')
           env.Program(source='bar.c')
           env.Program('bar.c')

       As a convenience, a srcdir keyword argument may be specified when
       calling a Builder. When specified, all source file strings that are not
       absolute paths or top-relative paths will be interpreted relative to
       the specified srcdir. The following example will build the build/prog
       (or build/prog.exe on Windows) program from the files src/f1.c and
       src/f2.c:

           env.Program('build/prog', ['f1.c', 'f2.c'], srcdir='src')

       Keyword arguments that are not specifically recognized are treated as
       construction variable overrides, which replace or add those variables
       on a limited basis. These overrides will only be in effect when
       building the target of the builder call, and will not affect other
       parts of the build. For example, if you want to specify some libraries
       needed by just one program:

           env.Program('hello', 'hello.c', LIBS=['gl', 'glut'])

       or generate a shared library with a non-standard suffix:

           env.SharedLibrary(
               target='word',
               source='word.cpp',
               SHLIBSUFFIX='.ocx',
               LIBSUFFIXES=['.ocx'],
           )

       Note that both the $SHLIBSUFFIX and $LIBSUFFIXES variables must be set
       if you want scons to search automatically for dependencies on the
       non-standard library names; see the descriptions below of these
       variables for more information.

       The optional parse_flags keyword argument is recognized by builders.
       This works similarly to the env.MergeFlags method, where the argument
       value is broken into individual settings and merged into the
       appropriate construction variables.

           env.Program('hello', 'hello.c', parse_flags='-Iinclude -DEBUG -lm')

       This example adds 'include' to CPPPATH, 'EBUG' to CPPDEFINES, and 'm'
       to LIBS.

       Although the builder methods defined by scons are, in fact, methods of
       a construction environment object, many may also be called without an
       explicit environment:

           Program('hello', 'hello.c')
           SharedLibrary('word', 'word.cpp')

       If called this way, methods will internally use the default environment
       that consists of the tools and values that scons has determined are
       appropriate for the local system.

       Builder methods that can be called without an explicit environment
       (indicated in the listing of builders without a leading env.) may be
       called from custom Python modules that you import into an SConscript
       file by adding the following to the Python module:

           from SCons.Script import *

       Builder methods return a NodeList, a list-like object whose elements
       are Nodes, SCons' internal representation of build targets or sources.
       See the section called "File and Directory Nodes" for more information.
       The returned NodeList object can be passed to other builder methods as
       source(s) or passed to any SCons function or method where a filename
       would normally be accepted.

       For example, to add a specific preprocessor define when compiling one
       specific object file but not the others:

           bar_obj_list = env.StaticObject('bar.c', CPPDEFINES='-DBAR')
           env.Program("prog", ['foo.c', bar_obj_list, 'main.c'])

       Using a Node as in this example makes for a more portable build by
       avoiding having to specify a platform-specific object suffix when
       calling the Program builder method.

       The NodeList object is also convenient to pass to the Default function,
       for the same reason of avoiding a platform-specific name:

           tgt = env.Program("prog", ["foo.c", "bar.c", "main.c"])
           Default(tgt)

       Builder calls will automatically "flatten" lists passed as source and
       target, so they are free to contain elements which are themselves
       lists, such as bar_obj_list returned by the StaticObject call above. If
       you need to manipulate a list of lists returned by builders directly in
       Python code, you can either build a new list by hand:

           foo = Object('foo.c')
           bar = Object('bar.c')
           objects = ['begin.o'] + foo + ['middle.o'] + bar + ['end.o']
           for obj in objects:
               print(str(obj))

       Or you can use the Flatten function supplied by scons to create a list
       containing just the Nodes, which may be more convenient:

           foo = Object('foo.c')
           bar = Object('bar.c')
           objects = Flatten(['begin.o', foo, 'middle.o', bar, 'end.o'])
           for obj in objects:
               print(str(obj))

       SCons builder calls return a list-like object, not an actual Python
       list, so it is not appropriate to use the Python add operator (+ or +=)
       to append builder results to a Python list. Because the list and the
       object are different types, Python will not update the original list in
       place, but will instead create a new NodeList object containing the
       concatenation of the list elements and the builder results. This will
       cause problems for any other Python variables in your SCons
       configuration that still hold on to a reference to the original list.
       Instead, use the Python list extend method to make sure the list is
       updated in-place. Example:

           object_files = []

           # Do NOT use += here:
           #    object_files += Object('bar.c')
           #
           # It will not update the object_files list in place.
           #
           # Instead, use the list extend method:
           object_files.extend(Object('bar.c'))

       The path name for a Node's file may be used by passing the Node to
       Python's builtin str function:

           bar_obj_list = env.StaticObject('bar.c', CPPDEFINES='-DBAR')
           print("The path to bar_obj is:", str(bar_obj_list[0]))

       Note that because the Builder call returns a NodeList, you have to
       access the first element in the list, (bar_obj_list[0] in the example)
       to get at the Node that actually represents the object file.

       Builder calls support a chdir keyword argument that specifies that the
       Builder's action(s) should be executed after changing directory. If the
       chdir argument is a string or a directory Node, scons will change to
       the specified directory. If the chdir is not a string or Node and is
       non-zero, then scons will change to the target file's directory.

           # scons will change to the "sub" subdirectory
           # before executing the "cp" command.
           env.Command('sub/dir/foo.out', 'sub/dir/foo.in',
                       "cp dir/foo.in dir/foo.out",
                       chdir='sub')

           # Because chdir is not a string, scons will change to the
           # target's directory ("sub/dir") before executing the
           # "cp" command.
           env.Command('sub/dir/foo.out', 'sub/dir/foo.in',
                       "cp foo.in foo.out",
                       chdir=1)

       Note that SCons will not automatically modify its expansion of
       construction variables like $TARGET and $SOURCE when using the chdir
       keyword argument--that is, the expanded file names will still be
       relative to the top-level directory where SConstruct was found, and
       consequently incorrect relative to the chdir directory. If you use the
       chdir keyword argument, you will typically need to supply a different
       command line using expansions like ${TARGET.file} and ${SOURCE.file} to
       use just the filename portion of the targets and source.

       When trying to handle errors that may occur in a builder method,
       consider that the corresponding Action is executed at a different time
       than the SConscript file statement calling the builder. It is not
       useful to wrap a builder call in a try block, since success in the
       builder call is not the same as the builder itself succeeding. If
       necessary, a Builder's Action should be coded to exit with a useful
       exception message indicating the problem in the SConscript files -
       programmatically recovering from build errors is rarely useful.

       scons predefines the following builder methods. Depending on the setup
       of a particular construction environment and on the type and software
       installation status of the underlying system, not all builders may be
       available to that construction environment.

       CFile(), env.CFile()
           Builds a C source file given a lex (.l) or yacc (.y) input file.
           The suffix specified by the $CFILESUFFIX construction variable (.c
           by default) is automatically added to the target if it is not
           already present. Example:

               # builds foo.c
               env.CFile(target = 'foo.c', source = 'foo.l')
               # builds bar.c
               env.CFile(target = 'bar', source = 'bar.y')

       Command(), env.Command()
           The Command "Builder" is actually a function that looks like a
           Builder, but takes a required third argument, which is the action
           to take to construct the target from the source, used for "one-off"
           builds where a full builder is not needed. Thus it does not follow
           the builder calling rules described at the start of this section.
           See instead the Command function description for the calling syntax
           and details.

       CompilationDatabase(), env.CompilationDatabase()

           CompilationDatabase is a special builder which adds a target to
           create a JSON formatted compilation database compatible with clang
           tooling (see the LLVM specification[1]). This database is suitable
           for consumption by various tools and editors who can use it to
           obtain build and dependency information which otherwise would be
           internal to SCons. The builder does not require any source files to
           be specified, rather it arranges to emit information about all of
           the C, C++ and assembler source/output pairs identified in the
           build that are not excluded by the optional filter
           $COMPILATIONDB_PATH_FILTER. The target is subject to the usual
           SCons target selection rules.

           If called with no arguments, the builder will default to a target
           name of compile_commands.json.

           If called with a single positional argument, scons will "deduce"
           the target name from that source argument, giving it the same name,
           and then ignore the source. This is the usual way to call the
           builder if a non-default target name is wanted.

           If called with either the target= or source= keyword arguments, the
           value of the argument is taken as the target name. If called with
           both, the target= value is used and source= is ignored. If called
           with multiple sources, the source list will be ignored, since there
           is no way to deduce what the intent was; in this case the default
           target name will be used.

               Note
               You must load the compilation_db tool prior to specifying any
               part of your build or some source/output files will not show up
               in the compilation database.
           Available since scons 4.0.

       CXXFile(), env.CXXFile()
           Builds a C++ source file given a lex (.ll) or yacc (.yy) input
           file. The suffix specified by the $CXXFILESUFFIX construction
           variable (.cc by default) is automatically added to the target if
           it is not already present. Example:

               # builds foo.cc
               env.CXXFile(target = 'foo.cc', source = 'foo.ll')
               # builds bar.cc
               env.CXXFile(target = 'bar', source = 'bar.yy')

       DocbookEpub(), env.DocbookEpub()
           A pseudo-Builder, providing a Docbook toolchain for EPUB output.

               env = Environment(tools=['docbook'])
               env.DocbookEpub('manual.epub', 'manual.xml')

           or simply

               env = Environment(tools=['docbook'])
               env.DocbookEpub('manual')

       DocbookHtml(), env.DocbookHtml()
           A pseudo-Builder, providing a Docbook toolchain for HTML output.

               env = Environment(tools=['docbook'])
               env.DocbookHtml('manual.html', 'manual.xml')

           or simply

               env = Environment(tools=['docbook'])
               env.DocbookHtml('manual')

       DocbookHtmlChunked(), env.DocbookHtmlChunked()
           A pseudo-Builder providing a Docbook toolchain for chunked HTML
           output. It supports the base.dir parameter. The chunkfast.xsl file
           (requires "EXSLT") is used as the default stylesheet. Basic syntax:

               env = Environment(tools=['docbook'])
               env.DocbookHtmlChunked('manual')

           where manual.xml is the input file.

           If you use the root.filename parameter in your own stylesheets you
           have to specify the new target name. This ensures that the
           dependencies get correct, especially for the cleanup via "scons
           -c":

               env = Environment(tools=['docbook'])
               env.DocbookHtmlChunked('mymanual.html', 'manual', xsl='htmlchunk.xsl')

           Some basic support for the base.dir parameter is provided. You can
           add the base_dir keyword to your Builder call, and the given prefix
           gets prepended to all the created filenames:

               env = Environment(tools=['docbook'])
               env.DocbookHtmlChunked('manual', xsl='htmlchunk.xsl', base_dir='output/')

           Make sure that you don't forget the trailing slash for the base
           folder, else your files get renamed only!

       DocbookHtmlhelp(), env.DocbookHtmlhelp()
           A pseudo-Builder, providing a Docbook toolchain for HTMLHELP
           output. Its basic syntax is:

               env = Environment(tools=['docbook'])
               env.DocbookHtmlhelp('manual')

           where manual.xml is the input file.

           If you use the root.filename parameter in your own stylesheets you
           have to specify the new target name. This ensures that the
           dependencies get correct, especially for the cleanup via "scons
           -c":

               env = Environment(tools=['docbook'])
               env.DocbookHtmlhelp('mymanual.html', 'manual', xsl='htmlhelp.xsl')

           Some basic support for the base.dir parameter is provided. You can
           add the base_dir keyword to your Builder call, and the given prefix
           gets prepended to all the created filenames:

               env = Environment(tools=['docbook'])
               env.DocbookHtmlhelp('manual', xsl='htmlhelp.xsl', base_dir='output/')

           Make sure that you don't forget the trailing slash for the base
           folder, else your files get renamed only!

       DocbookMan(), env.DocbookMan()
           A pseudo-Builder, providing a Docbook toolchain for Man page
           output. Its basic syntax is:

               env = Environment(tools=['docbook'])
               env.DocbookMan('manual')

           where manual.xml is the input file. Note, that you can specify a
           target name, but the actual output names are automatically set from
           the refname entries in your XML source.

       DocbookPdf(), env.DocbookPdf()
           A pseudo-Builder, providing a Docbook toolchain for PDF output.

               env = Environment(tools=['docbook'])
               env.DocbookPdf('manual.pdf', 'manual.xml')

           or simply

               env = Environment(tools=['docbook'])
               env.DocbookPdf('manual')

       DocbookSlidesHtml(), env.DocbookSlidesHtml()
           A pseudo-Builder, providing a Docbook toolchain for HTML slides
           output.

               env = Environment(tools=['docbook'])
               env.DocbookSlidesHtml('manual')

           If you use the titlefoil.html parameter in your own stylesheets you
           have to give the new target name. This ensures that the
           dependencies get correct, especially for the cleanup via "scons
           -c":

               env = Environment(tools=['docbook'])
               env.DocbookSlidesHtml('mymanual.html','manual', xsl='slideshtml.xsl')

           Some basic support for the base.dir parameter is provided. You can
           add the base_dir keyword to your Builder call, and the given prefix
           gets prepended to all the created filenames:

               env = Environment(tools=['docbook'])
               env.DocbookSlidesHtml('manual', xsl='slideshtml.xsl', base_dir='output/')

           Make sure that you don't forget the trailing slash for the base
           folder, else your files get renamed only!

       DocbookSlidesPdf(), env.DocbookSlidesPdf()
           A pseudo-Builder, providing a Docbook toolchain for PDF slides
           output.

               env = Environment(tools=['docbook'])
               env.DocbookSlidesPdf('manual.pdf', 'manual.xml')

           or simply

               env = Environment(tools=['docbook'])
               env.DocbookSlidesPdf('manual')

       DocbookXInclude(), env.DocbookXInclude()
           A pseudo-Builder, for resolving XIncludes in a separate processing
           step.

               env = Environment(tools=['docbook'])
               env.DocbookXInclude('manual_xincluded.xml', 'manual.xml')

       DocbookXslt(), env.DocbookXslt()
           A pseudo-Builder, applying a given XSL transformation to the input
           file.

               env = Environment(tools=['docbook'])
               env.DocbookXslt('manual_transformed.xml', 'manual.xml', xsl='transform.xslt')

           Note, that this builder requires the xsl parameter to be set.

       DVI(), env.DVI()
           Builds a .dvi file from a .tex, .ltx or .latex input file. If the
           source file suffix is .tex, scons will examine the contents of the
           file; if the string \documentclass or \documentstyle is found, the
           file is assumed to be a LaTeX file and the target is built by
           invoking the $LATEXCOM command line; otherwise, the $TEXCOM command
           line is used. If the file is a LaTeX file, the DVI builder method
           will also examine the contents of the .aux file and invoke the
           $BIBTEX command line if the string bibdata is found, start
           $MAKEINDEX to generate an index if a .ind file is found and will
           examine the contents .log file and re-run the $LATEXCOM command if
           the log file says it is necessary.

           The suffix .dvi (hard-coded within TeX itself) is automatically
           added to the target if it is not already present. Examples:

               # builds from aaa.tex
               env.DVI(target = 'aaa.dvi', source = 'aaa.tex')
               # builds bbb.dvi
               env.DVI(target = 'bbb', source = 'bbb.ltx')
               # builds from ccc.latex
               env.DVI(target = 'ccc.dvi', source = 'ccc.latex')

       Gs(), env.Gs()
           A Builder for explicitly calling the gs executable. Depending on
           the underlying OS, the different names gs, gsos2 and gswin32c are
           tried.

               env = Environment(tools=['gs'])
               env.Gs(
                   'cover.jpg',
                   'scons-scons.pdf',
                   GSFLAGS='-dNOPAUSE -dBATCH -sDEVICE=jpeg -dFirstPage=1 -dLastPage=1 -q',
               )

       Install(), env.Install()
           Installs one or more source files or directories in the specified
           target, which must be a directory. The names of the specified
           source files or directories remain the same within the destination
           directory. The sources may be given as a string or as a node
           returned by a builder.

               env.Install(target='/usr/local/bin', source=['foo', 'bar'])

           Note that if target paths chosen for the Install builder (and the
           related InstallAs and InstallVersionedLib builders) are outside the
           project tree, such as in the example above, they may not be
           selected for "building" by default, since in the absence of other
           instructions scons builds targets that are underneath the top
           directory (the directory that contains the SConstruct file, usually
           the current directory). Use command line targets or the Default
           function in this case.

           If the --install-sandbox command line option is given, the target
           directory will be prefixed by the directory path specified. This is
           useful to test installs without installing to a "live" location in
           the system.

           See also FindInstalledFiles. For more thoughts on installation, see
           the User Guide (particularly the section on Command-Line Targets
           and the chapters on Installing Files and on Alias Targets).

       InstallAs(), env.InstallAs()
           Installs one or more source files or directories to specific names,
           allowing changing a file or directory name as part of the
           installation. It is an error if the target and source arguments
           list different numbers of files or directories.

               env.InstallAs(target='/usr/local/bin/foo',
                             source='foo_debug')
               env.InstallAs(target=['../lib/libfoo.a', '../lib/libbar.a'],
                             source=['libFOO.a', 'libBAR.a'])

           See the note under Install.

       InstallVersionedLib(), env.InstallVersionedLib()
           Installs a versioned shared library. The symlinks appropriate to
           the architecture will be generated based on symlinks of the source
           library.

               env.InstallVersionedLib(target='/usr/local/bin/foo',
                                       source='libxyz.1.5.2.so')

           See the note under Install.

       Jar(), env.Jar()
           Builds a Java archive (.jar) file from the specified list of
           sources. Any directories in the source list will be searched for
           .class files). Any .java files in the source list will be compiled
           to .class files by calling the Java Builder.

           If the $JARCHDIR value is set, the jar command will change to the
           specified directory using the -C option. If $JARCHDIR is not set
           explicitly, SCons will use the top of any subdirectory tree in
           which Java .class were built by the Java Builder.

           If the contents any of the source files begin with the string
           Manifest-Version, the file is assumed to be a manifest and is
           passed to the jar command with the m option set.

               env.Jar(target = 'foo.jar', source = 'classes')

               env.Jar(target = 'bar.jar',
                       source = ['bar1.java', 'bar2.java'])

       Java(), env.Java()
           Builds one or more Java class files. The sources may be any
           combination of explicit .java files, or directory trees which will
           be scanned for .java files.

           SCons will parse each source .java file to find the classes
           (including inner classes) defined within that file, and from that
           figure out the target .class files that will be created. The class
           files will be placed underneath the specified target directory.

           SCons will also search each Java file for the Java package name,
           which it assumes can be found on a line beginning with the string
           package in the first column; the resulting .class files will be
           placed in a directory reflecting the specified package name. For
           example, the file Foo.java defining a single public Foo class and
           containing a package name of sub.dir will generate a corresponding
           sub/dir/Foo.class class file.

           Examples:

               env.Java(target = 'classes', source = 'src')
               env.Java(target = 'classes', source = ['src1', 'src2'])
               env.Java(target = 'classes', source = ['File1.java', 'File2.java'])


           Java source files can use the native encoding for the underlying
           OS. Since SCons compiles in simple ASCII mode by default, the
           compiler will generate warnings about unmappable characters, which
           may lead to errors as the file is processed further. In this case,
           the user must specify the LANG environment variable to tell the
           compiler what encoding is used. For portibility, it's best if the
           encoding is hard-coded so that the compile will work if it is done
           on a system with a different encoding.

               env = Environment()
               env['ENV']['LANG'] = 'en_GB.UTF-8'


       JavaH(), env.JavaH()
           Builds C header and source files for implementing Java native
           methods. The target can be either a directory in which the header
           files will be written, or a header file name which will contain all
           of the definitions. The source can be the names of .class files,
           the names of .java files to be compiled into .class files by
           calling the Java builder method, or the objects returned from the
           Java builder method.

           If the construction variable $JAVACLASSDIR is set, either in the
           environment or in the call to the JavaH builder method itself, then
           the value of the variable will be stripped from the beginning of
           any .class file names.

           Examples:

               # builds java_native.h
               classes = env.Java(target="classdir", source="src")
               env.JavaH(target="java_native.h", source=classes)

               # builds include/package_foo.h and include/package_bar.h
               env.JavaH(target="include", source=["package/foo.class", "package/bar.class"])

               # builds export/foo.h and export/bar.h
               env.JavaH(
                   target="export",
                   source=["classes/foo.class", "classes/bar.class"],
                   JAVACLASSDIR="classes",
               )

       Library(), env.Library()
           A synonym for the StaticLibrary builder method.

       LoadableModule(), env.LoadableModule()
           On most systems, this is the same as SharedLibrary. On Mac OS X
           (Darwin) platforms, this creates a loadable module bundle.

       M4(), env.M4()
           Builds an output file from an M4 input file. This uses a default
           $M4FLAGS value of -E, which considers all warnings to be fatal and
           stops on the first warning when using the GNU version of m4.
           Example:

               env.M4(target = 'foo.c', source = 'foo.c.m4')

       Moc(), env.Moc()
           Builds an output file from a moc input file. Moc input files are
           either header files or cxx files. This builder is only available
           after using the tool 'qt'. See the $QTDIR variable for more
           information. Example:

               env.Moc('foo.h') # generates moc_foo.cc
               env.Moc('foo.cpp') # generates foo.moc

       MOFiles(), env.MOFiles()
           This builder belongs to msgfmt tool. The builder compiles PO files
           to MO files.


           Example 1. Create pl.mo and en.mo by compiling pl.po and en.po:

                 # ...
                 env.MOFiles(['pl', 'en'])


           Example 2. Compile files for languages defined in LINGUAS file:

                 # ...
                 env.MOFiles(LINGUAS_FILE = 1)


           Example 3. Create pl.mo and en.mo by compiling pl.po and en.po plus
           files for languages defined in LINGUAS file:

                 # ...
                 env.MOFiles(['pl', 'en'], LINGUAS_FILE = 1)


           Example 4. Compile files for languages defined in LINGUAS file
           (another version):

                 # ...
                 env['LINGUAS_FILE'] = 1
                 env.MOFiles()

       MSVSProject(), env.MSVSProject()
           Builds a Microsoft Visual Studio project file, and by default
           builds a solution file as well.

           This builds a Visual Studio project file, based on the version of
           Visual Studio that is configured (either the latest installed
           version, or the version specified by $MSVS_VERSION in the
           Environment constructor). For Visual Studio 6, it will generate a
           .dsp file. For Visual Studio 7, 8, and 9, it will generate a
           .vcproj file. For Visual Studio 10 and later, it will generate a
           .vcxproj file.

           By default, this also generates a solution file for the specified
           project, a .dsw file for Visual Studio 6 or a .sln file for Visual
           Studio 7 and later. This behavior may be disabled by specifying
           auto_build_solution=0 when you call MSVSProject, in which case you
           presumably want to build the solution file(s) by calling the
           MSVSSolution Builder (see below).

           The MSVSProject builder takes several lists of filenames to be
           placed into the project file. These are currently limited to srcs,
           incs, localincs, resources, and misc. These are pretty
           self-explanatory, but it should be noted that these lists are added
           to the $SOURCES construction variable as strings, NOT as SCons File
           Nodes. This is because they represent file names to be added to the
           project file, not the source files used to build the project file.

           The above filename lists are all optional, although at least one
           must be specified for the resulting project file to be non-empty.

           In addition to the above lists of values, the following values may
           be specified:

           target
               The name of the target .dsp or .vcproj file. The correct suffix
               for the version of Visual Studio must be used, but the
               $MSVSPROJECTSUFFIX construction variable will be defined to the
               correct value (see example below).

           variant
               The name of this particular variant. For Visual Studio 7
               projects, this can also be a list of variant names. These are
               typically things like "Debug" or "Release", but really can be
               anything you want. For Visual Studio 7 projects, they may also
               specify a target platform separated from the variant name by a
               | (vertical pipe) character: Debug|Xbox. The default target
               platform is Win32. Multiple calls to MSVSProject with different
               variants are allowed; all variants will be added to the project
               file with their appropriate build targets and sources.

           cmdargs
               Additional command line arguments for the different variants.
               The number of cmdargs entries must match the number of variant
               entries, or be empty (not specified). If you give only one, it
               will automatically be propagated to all variants.

           cppdefines
               Preprocessor definitions for the different variants. The number
               of cppdefines entries must match the number of variant entries,
               or be empty (not specified). If you give only one, it will
               automatically be propagated to all variants. If you don't give
               this parameter, SCons will use the invoking environment's
               CPPDEFINES entry for all variants.

           cppflags
               Compiler flags for the different variants. If a /std:c++ flag
               is found then /Zc:__cplusplus is appended to the flags if not
               already found, this ensures that intellisense uses the /std:c++
               switch. The number of cppflags entries must match the number of
               variant entries, or be empty (not specified). If you give only
               one, it will automatically be propagated to all variants. If
               you don't give this parameter, SCons will combine the invoking
               environment's CCFLAGS, CXXFLAGS, CPPFLAGS entries for all
               variants.

           cpppaths
               Compiler include paths for the different variants. The number
               of cpppaths entries must match the number of variant entries,
               or be empty (not specified). If you give only one, it will
               automatically be propagated to all variants. If you don't give
               this parameter, SCons will use the invoking environment's
               CPPPATH entry for all variants.

           buildtarget
               An optional string, node, or list of strings or nodes (one per
               build variant), to tell the Visual Studio debugger what output
               target to use in what build variant. The number of buildtarget
               entries must match the number of variant entries.

           runfile
               The name of the file that Visual Studio 7 and later will run
               and debug. This appears as the value of the Output field in the
               resulting Visual Studio project file. If this is not specified,
               the default is the same as the specified buildtarget value.

           Note that because SCons always executes its build commands from the
           directory in which the SConstruct file is located, if you generate
           a project file in a different directory than the SConstruct
           directory, users will not be able to double-click on the file name
           in compilation error messages displayed in the Visual Studio
           console output window. This can be remedied by adding the Visual
           C/C++ /FC compiler option to the $CCFLAGS variable so that the
           compiler will print the full path name of any files that cause
           compilation errors.

           Example usage:

               barsrcs = ['bar.cpp']
               barincs = ['bar.h']
               barlocalincs = ['StdAfx.h']
               barresources = ['bar.rc','resource.h']
               barmisc = ['bar_readme.txt']

               dll = env.SharedLibrary(target='bar.dll',
                                       source=barsrcs)
               buildtarget = [s for s in dll if str(s).endswith('dll')]
               env.MSVSProject(target='Bar' + env['MSVSPROJECTSUFFIX'],
                               srcs=barsrcs,
                               incs=barincs,
                               localincs=barlocalincs,
                               resources=barresources,
                               misc=barmisc,
                               buildtarget=buildtarget,
                               variant='Release')


           Starting with version 2.4 of SCons it is also possible to specify
           the optional argument DebugSettings, which creates files for
           debugging under Visual Studio:

           DebugSettings
               A dictionary of debug settings that get written to the
               .vcproj.user or the .vcxproj.user file, depending on the
               version installed. As it is done for cmdargs (see above), you
               can specify a DebugSettings dictionary per variant. If you give
               only one, it will be propagated to all variants.

           Currently, only Visual Studio v9.0 and Visual Studio version v11
           are implemented, for other versions no file is generated. To
           generate the user file, you just need to add a DebugSettings
           dictionary to the environment with the right parameters for your
           MSVS version. If the dictionary is empty, or does not contain any
           good value, no file will be generated.

           Following is a more contrived example, involving the setup of a
           project for variants and DebugSettings:

               # Assuming you store your defaults in a file
               vars = Variables('variables.py')
               msvcver = vars.args.get('vc', '9')

               # Check command args to force one Microsoft Visual Studio version
               if msvcver == '9' or msvcver == '11':
                 env = Environment(MSVC_VERSION=msvcver+'.0', MSVC_BATCH=False)
               else:
                 env = Environment()

               AddOption('--userfile', action='store_true', dest='userfile', default=False,
                         help="Create Visual Studio Project user file")

               #
               # 1. Configure your Debug Setting dictionary with options you want in the list
               # of allowed options, for instance if you want to create a user file to launch
               # a specific application for testing your dll with Microsoft Visual Studio 2008 (v9):
               #
               V9DebugSettings = {
                   'Command':'c:\\myapp\\using\\thisdll.exe',
                   'WorkingDirectory': 'c:\\myapp\\using\\',
                   'CommandArguments': '-p password',
               #     'Attach':'false',
               #     'DebuggerType':'3',
               #     'Remote':'1',
               #     'RemoteMachine': None,
               #     'RemoteCommand': None,
               #     'HttpUrl': None,
               #     'PDBPath': None,
               #     'SQLDebugging': None,
               #     'Environment': '',
               #     'EnvironmentMerge':'true',
               #     'DebuggerFlavor': None,
               #     'MPIRunCommand': None,
               #     'MPIRunArguments': None,
               #     'MPIRunWorkingDirectory': None,
               #     'ApplicationCommand': None,
               #     'ApplicationArguments': None,
               #     'ShimCommand': None,
               #     'MPIAcceptMode': None,
               #     'MPIAcceptFilter': None,
               }

               #
               # 2. Because there are a lot of different options depending on the Microsoft
               # Visual Studio version, if you use more than one version you have to
               # define a dictionary per version, for instance if you want to create a user
               # file to launch a specific application for testing your dll with Microsoft
               # Visual Studio 2012 (v11):
               #
               V10DebugSettings = {
                   'LocalDebuggerCommand': 'c:\\myapp\\using\\thisdll.exe',
                   'LocalDebuggerWorkingDirectory': 'c:\\myapp\\using\\',
                   'LocalDebuggerCommandArguments': '-p password',
               #     'LocalDebuggerEnvironment': None,
               #     'DebuggerFlavor': 'WindowsLocalDebugger',
               #     'LocalDebuggerAttach': None,
               #     'LocalDebuggerDebuggerType': None,
               #     'LocalDebuggerMergeEnvironment': None,
               #     'LocalDebuggerSQLDebugging': None,
               #     'RemoteDebuggerCommand': None,
               #     'RemoteDebuggerCommandArguments': None,
               #     'RemoteDebuggerWorkingDirectory': None,
               #     'RemoteDebuggerServerName': None,
               #     'RemoteDebuggerConnection': None,
               #     'RemoteDebuggerDebuggerType': None,
               #     'RemoteDebuggerAttach': None,
               #     'RemoteDebuggerSQLDebugging': None,
               #     'DeploymentDirectory': None,
               #     'AdditionalFiles': None,
               #     'RemoteDebuggerDeployDebugCppRuntime': None,
               #     'WebBrowserDebuggerHttpUrl': None,
               #     'WebBrowserDebuggerDebuggerType': None,
               #     'WebServiceDebuggerHttpUrl': None,
               #     'WebServiceDebuggerDebuggerType': None,
               #     'WebServiceDebuggerSQLDebugging': None,
               }

               #
               # 3. Select the dictionary you want depending on the version of visual Studio
               # Files you want to generate.
               #
               if not env.GetOption('userfile'):
                   dbgSettings = None
               elif env.get('MSVC_VERSION', None) == '9.0':
                   dbgSettings = V9DebugSettings
               elif env.get('MSVC_VERSION', None) == '11.0':
                   dbgSettings = V10DebugSettings
               else:
                   dbgSettings = None

               #
               # 4. Add the dictionary to the DebugSettings keyword.
               #
               barsrcs = ['bar.cpp', 'dllmain.cpp', 'stdafx.cpp']
               barincs = ['targetver.h']
               barlocalincs = ['StdAfx.h']
               barresources = ['bar.rc','resource.h']
               barmisc = ['ReadMe.txt']

               dll = env.SharedLibrary(target='bar.dll',
                                       source=barsrcs)

               env.MSVSProject(target='Bar' + env['MSVSPROJECTSUFFIX'],
                               srcs=barsrcs,
                               incs=barincs,
                               localincs=barlocalincs,
                               resources=barresources,
                               misc=barmisc,
                               buildtarget=[dll[0]] * 2,
                               variant=('Debug|Win32', 'Release|Win32'),
                               cmdargs='vc=%s' %  msvcver,
                               DebugSettings=(dbgSettings, {}))


       MSVSSolution(), env.MSVSSolution()
           Builds a Microsoft Visual Studio solution file.

           This builds a Visual Studio solution file, based on the version of
           Visual Studio that is configured (either the latest installed
           version, or the version specified by $MSVS_VERSION in the
           construction environment). For Visual Studio 6, it will generate a
           .dsw file. For Visual Studio 7 (.NET), it will generate a .sln
           file.

           The following values must be specified:

           target
               The name of the target .dsw or .sln file. The correct suffix
               for the version of Visual Studio must be used, but the value
               $MSVSSOLUTIONSUFFIX will be defined to the correct value (see
               example below).

           variant
               The name of this particular variant, or a list of variant names
               (the latter is only supported for MSVS 7 solutions). These are
               typically things like "Debug" or "Release", but really can be
               anything you want. For MSVS 7 they may also specify target
               platform, like this "Debug|Xbox". Default platform is Win32.

           projects
               A list of project file names, or Project nodes returned by
               calls to the MSVSProject Builder, to be placed into the
               solution file. It should be noted that these file names are NOT
               added to the $SOURCES environment variable in form of files,
               but rather as strings. This is because they represent file
               names to be added to the solution file, not the source files
               used to build the solution file.

           Example Usage:

               env.MSVSSolution(
                   target="Bar" + env["MSVSSOLUTIONSUFFIX"],
                   projects=["bar" + env["MSVSPROJECTSUFFIX"]],
                   variant="Release",
               )


       Ninja(), env.Ninja()

           Ninja is a special builder which adds a target to create a ninja
           build file. The builder does not require any source files to be
           specified.

               Note
               This is an experimental feature. To enable it you must use one
               of the following methods

                       # On the command line
                       --experimental=ninja

                       # Or in your SConstruct
                       SetOption('experimental', 'ninja')


               This functionality is subject to change and/or removal without
               deprecation cycle.

               To use this tool you must install pypi's ninja package[2]. This
               can be done via pip install ninja
           If called with no arguments, the builder will default to a target
           name of ninja.build.

           If called with a single positional argument, scons will "deduce"
           the target name from that source argument, giving it the same name,
           and then ignore the source. This is the usual way to call the
           builder if a non-default target name is wanted.

           If called with either the target= or source= keyword arguments, the
           value of the argument is taken as the target name. If called with
           both, the target= value is used and source= is ignored. If called
           with multiple sources, the source list will be ignored, since there
           is no way to deduce what the intent was; in this case the default
           target name will be used.


           Available since scons 4.2.

       Object(), env.Object()
           A synonym for the StaticObject builder method.

       Package(), env.Package()
           Builds software distribution packages. A package is a container
           format which includes files to install along with metadata.
           Packaging is optional, and must be enabled by specifying the
           packaging tool. For example:

               env = Environment(tools=['default', 'packaging'])


           SCons can build packages in a number of well known packaging
           formats. The target package type may be selected with the the
           $PACKAGETYPE construction variable or the --package-type command
           line option. The package type may be a list, in which case SCons
           will attempt to build packages for each type in the list. Example:

               env.Package(PACKAGETYPE=['src_zip', 'src_targz'], ...other args...)

           The currently supported packagers are:

           +-----------+----------------------------+
           |msi        | Microsoft Installer        |
           |           | package                    |
           +-----------+----------------------------+
           |rpm        | RPM Package Manger package |
           +-----------+----------------------------+
           |ipkg       | Itsy Package Management    |
           |           | package                    |
           +-----------+----------------------------+
           |tarbz2     | bzip2-compressed tar file  |
           +-----------+----------------------------+
           |targz      | gzip-compressed tar file   |
           +-----------+----------------------------+
           |tarxz      | xz-compressed tar file     |
           +-----------+----------------------------+
           |zip        | zip file                   |
           +-----------+----------------------------+
           |src_tarbz2 | bzip2-compressed tar file  |
           |           | suitable as source to      |
           |           | another packager           |
           +-----------+----------------------------+
           |src_targz  | gzip-compressed tar file   |
           |           | suitable as source to      |
           |           | another packager           |
           +-----------+----------------------------+
           |src_tarxz  | xz-compressed tar file     |
           |           | suitable as source to      |
           |           | another packager           |
           +-----------+----------------------------+
           |src_zip    | zip file suitable as       |
           |           | source to another packager |
           +-----------+----------------------------+
           The file list to include in the package may be specified with the
           source keyword argument. If omitted, the FindInstalledFiles
           function is called behind the scenes to select all files that have
           an Install, InstallAs or InstallVersionedLib Builder attached. If
           the target keyword argument is omitted, the target name(s) will be
           deduced from the package type(s).

           The metadata comes partly from attributes of the files to be
           packaged, and partly from packaging tags. Tags can be passed as
           keyword arguments to the Package builder call, and may also be
           attached to files (or more accurately, Nodes representing files)
           with the Tag function. Some package-level tags are mandatory, and
           will lead to errors if omitted. The mandatory tags vary depending
           on the package type.

           While packaging, the builder uses a temporary location named by the
           value of the $PACKAGEROOT variable - the package sources are copied
           there before packaging.

           Packaging example:

               env = Environment(tools=["default", "packaging"])
               env.Install("/bin/", "my_program")
               env.Package(
                   NAME="foo",
                   VERSION="1.2.3",
                   PACKAGEVERSION=0,
                   PACKAGETYPE="rpm",
                   LICENSE="gpl",
                   SUMMARY="balalalalal",
                   DESCRIPTION="this should be really really long",
                   X_RPM_GROUP="Application/fu",
                   SOURCE_URL="https://foo.org/foo-1.2.3.tar.gz",
               )

           In this example, the target /bin/my_program created by the Install
           call would not be built by default since it is not under the
           project top directory. However, since no source is specified to the
           Package builder, it is selected for packaging by the default
           sources rule. Since packaging is done using $PACKAGEROOT, no write
           is actually done to the system's /bin directory, and the target
           will be selected since after rebasing to underneath $PACKAGEROOT it
           is now under the top directory of the project.

       PCH(), env.PCH()
           Builds a Microsoft Visual C++ precompiled header. Calling this
           builder returns a list of two targets: the PCH as the first
           element, and the object file as the second element. Normally the
           object file is ignored. This builder is only provided when
           Microsoft Visual C++ is being used as the compiler. The PCH builder
           is generally used in conjunction with the $PCH construction
           variable to force object files to use the precompiled header:

               env['PCH'] = env.PCH('StdAfx.cpp')[0]

       PDF(), env.PDF()
           Builds a .pdf file from a .dvi input file (or, by extension, a
           .tex, .ltx, or .latex input file). The suffix specified by the
           $PDFSUFFIX construction variable (.pdf by default) is added
           automatically to the target if it is not already present. Example:

               # builds from aaa.tex
               env.PDF(target = 'aaa.pdf', source = 'aaa.tex')
               # builds bbb.pdf from bbb.dvi
               env.PDF(target = 'bbb', source = 'bbb.dvi')

       POInit(), env.POInit()
           This builder belongs to msginit tool. The builder initializes
           missing PO file(s) if $POAUTOINIT is set. If $POAUTOINIT is not set
           (default), POInit prints instruction for user (that is supposed to
           be a translator), telling how the PO file should be initialized. In
           normal projects you should not use POInit and use POUpdate instead.
           POUpdate chooses intelligently between msgmerge(1) and msginit(1).
           POInit always uses msginit(1) and should be regarded as builder for
           special purposes or for temporary use (e.g. for quick, one time
           initialization of a bunch of PO files) or for tests.

           Target nodes defined through POInit are not built by default
           (they're Ignored from '.' node) but are added to special Alias
           ('po-create' by default). The alias name may be changed through the
           $POCREATE_ALIAS construction variable. All PO files defined through
           POInit may be easily initialized by scons po-create.


           Example 1. Initialize en.po and pl.po from messages.pot:

                 # ...
                 env.POInit(['en', 'pl']) # messages.pot --> [en.po, pl.po]


           Example 2. Initialize en.po and pl.po from foo.pot:

                 # ...
                 env.POInit(['en', 'pl'], ['foo']) # foo.pot --> [en.po, pl.po]


           Example 3. Initialize en.po and pl.po from foo.pot but using
           $POTDOMAIN construction variable:

                 # ...
                 env.POInit(['en', 'pl'], POTDOMAIN='foo') # foo.pot --> [en.po, pl.po]


           Example 4. Initialize PO files for languages defined in LINGUAS
           file. The files will be initialized from template messages.pot:

                 # ...
                 env.POInit(LINGUAS_FILE = 1) # needs 'LINGUAS' file


           Example 5. Initialize en.po and pl.pl PO files plus files for
           languages defined in LINGUAS file. The files will be initialized
           from template messages.pot:

                 # ...
                 env.POInit(['en', 'pl'], LINGUAS_FILE = 1)


           Example 6. You may preconfigure your environment first, and then
           initialize PO files:

                 # ...
                 env['POAUTOINIT'] = 1
                 env['LINGUAS_FILE'] = 1
                 env['POTDOMAIN'] = 'foo'
                 env.POInit()

           which has same efect as:

                 # ...
                 env.POInit(POAUTOINIT = 1, LINGUAS_FILE = 1, POTDOMAIN = 'foo')

       PostScript(), env.PostScript()
           Builds a .ps file from a .dvi input file (or, by extension, a .tex,
           .ltx, or .latex input file). The suffix specified by the $PSSUFFIX
           construction variable (.ps by default) is added automatically to
           the target if it is not already present. Example:

               # builds from aaa.tex
               env.PostScript(target = 'aaa.ps', source = 'aaa.tex')
               # builds bbb.ps from bbb.dvi
               env.PostScript(target = 'bbb', source = 'bbb.dvi')

       POTUpdate(), env.POTUpdate()
           The builder belongs to xgettext tool. The builder updates target
           POT file if exists or creates one if it doesn't. The node is not
           built by default (i.e. it is Ignored from '.'), but only on demand
           (i.e. when given POT file is required or when special alias is
           invoked). This builder adds its targe node (messages.pot, say) to a
           special alias (pot-update by default, see $POTUPDATE_ALIAS) so you
           can update/create them easily with scons pot-update. The file is
           not written until there is no real change in internationalized
           messages (or in comments that enter POT file).


               Note
               You may see xgettext(1) being invoked by the xgettext tool even
               if there is no real change in internationalized messages (so
               the POT file is not being updated). This happens every time a
               source file has changed. In such case we invoke xgettext(1) and
               compare its output with the content of POT file to decide
               whether the file should be updated or not.


           Example 1.  Let's create po/ directory and place following
           SConstruct script there:

                 # SConstruct in 'po/' subdir
                 env = Environment( tools = ['default', 'xgettext'] )
                 env.POTUpdate(['foo'], ['../a.cpp', '../b.cpp'])
                 env.POTUpdate(['bar'], ['../c.cpp', '../d.cpp'])

           Then invoke scons few times:

                 user@host:$ scons             # Does not create foo.pot nor bar.pot
                 user@host:$ scons foo.pot     # Updates or creates foo.pot
                 user@host:$ scons pot-update  # Updates or creates foo.pot and bar.pot
                 user@host:$ scons -c          # Does not clean foo.pot nor bar.pot.

           the results shall be as the comments above say.


           Example 2.  The POTUpdate builder may be used with no target
           specified, in which case default target messages.pot will be used.
           The default target may also be overridden by setting $POTDOMAIN
           construction variable or providing it as an override to POTUpdate
           builder:


                 # SConstruct script
                 env = Environment( tools = ['default', 'xgettext'] )
                 env['POTDOMAIN'] = "foo"
                 env.POTUpdate(source = ["a.cpp", "b.cpp"]) # Creates foo.pot ...
                 env.POTUpdate(POTDOMAIN = "bar", source = ["c.cpp", "d.cpp"]) # and bar.pot


           Example 3.  The sources may be specified within separate file, for
           example POTFILES.in:


                 # POTFILES.in in 'po/' subdirectory
                 ../a.cpp
                 ../b.cpp
                 # end of file

           The name of the file (POTFILES.in) containing the list of sources
           is provided via $XGETTEXTFROM:


                 # SConstruct file in 'po/' subdirectory
                 env = Environment( tools = ['default', 'xgettext'] )
                 env.POTUpdate(XGETTEXTFROM = 'POTFILES.in')


           Example 4.  You may use $XGETTEXTPATH to define source search path.
           Assume, for example, that you have files a.cpp, b.cpp,
           po/SConstruct, po/POTFILES.in. Then your POT-related files could
           look as below:

                 # POTFILES.in in 'po/' subdirectory
                 a.cpp
                 b.cpp
                 # end of file

                 # SConstruct file in 'po/' subdirectory
                 env = Environment( tools = ['default', 'xgettext'] )
                 env.POTUpdate(XGETTEXTFROM = 'POTFILES.in', XGETTEXTPATH='../')


           Example 5.  Multiple search directories may be defined within a
           list, i.e.  XGETTEXTPATH = ['dir1', 'dir2', ...]. The order in the
           list determines the search order of source files. The path to the
           first file found is used.

           Let's create 0/1/po/SConstruct script:

                 # SConstruct file in '0/1/po/' subdirectory
                 env = Environment( tools = ['default', 'xgettext'] )
                 env.POTUpdate(XGETTEXTFROM = 'POTFILES.in', XGETTEXTPATH=['../', '../../'])

           and 0/1/po/POTFILES.in:

                 # POTFILES.in in '0/1/po/' subdirectory
                 a.cpp
                 # end of file

           Write two *.cpp files, the first one is 0/a.cpp:

                 /* 0/a.cpp */
                 gettext("Hello from ../../a.cpp")

           and the second is 0/1/a.cpp:

                 /* 0/1/a.cpp */
                 gettext("Hello from ../a.cpp")

           then run scons. You'll obtain 0/1/po/messages.pot with the message
           "Hello from ../a.cpp". When you reverse order in $XGETTEXTFOM, i.e.
           when you write SConscript as

                 # SConstruct file in '0/1/po/' subdirectory
                 env = Environment( tools = ['default', 'xgettext'] )
                 env.POTUpdate(XGETTEXTFROM = 'POTFILES.in', XGETTEXTPATH=['../../', '../'])

           then the messages.pot will contain msgid "Hello from ../../a.cpp"
           line and not msgid "Hello from ../a.cpp".

       POUpdate(), env.POUpdate()
           The builder belongs to msgmerge tool. The builder updates PO files
           with msgmerge(1), or initializes missing PO files as described in
           documentation of msginit tool and POInit builder (see also
           $POAUTOINIT). Note, that POUpdate does not add its targets to
           po-create alias as POInit does.

           Target nodes defined through POUpdate are not built by default
           (they're Ignored from '.' node). Instead, they are added
           automatically to special Alias ('po-update' by default). The alias
           name may be changed through the $POUPDATE_ALIAS construction
           variable. You can easily update PO files in your project by scons
           po-update.


           Example 1.  Update en.po and pl.po from messages.pot template (see
           also $POTDOMAIN), assuming that the later one exists or there is
           rule to build it (see POTUpdate):

                 # ...
                 env.POUpdate(['en','pl']) # messages.pot --> [en.po, pl.po]


           Example 2.  Update en.po and pl.po from foo.pot template:

                 # ...
                 env.POUpdate(['en', 'pl'], ['foo']) # foo.pot -->  [en.po, pl.pl]


           Example 3.  Update en.po and pl.po from foo.pot (another version):

                 # ...
                 env.POUpdate(['en', 'pl'], POTDOMAIN='foo') # foo.pot -- > [en.po, pl.pl]


           Example 4.  Update files for languages defined in LINGUAS file. The
           files are updated from messages.pot template:

                 # ...
                 env.POUpdate(LINGUAS_FILE = 1) # needs 'LINGUAS' file


           Example 5.  Same as above, but update from foo.pot template:

                 # ...
                 env.POUpdate(LINGUAS_FILE = 1, source = ['foo'])


           Example 6.  Update en.po and pl.po plus files for languages defined
           in LINGUAS file. The files are updated from messages.pot template:

                 # produce 'en.po', 'pl.po' + files defined in 'LINGUAS':
                 env.POUpdate(['en', 'pl' ], LINGUAS_FILE = 1)


           Example 7.  Use $POAUTOINIT to automatically initialize PO file if
           it doesn't exist:

                 # ...
                 env.POUpdate(LINGUAS_FILE = 1, POAUTOINIT = 1)


           Example 8.  Update PO files for languages defined in LINGUAS file.
           The files are updated from foo.pot template. All necessary settings
           are pre-configured via environment.

                 # ...
                 env['POAUTOINIT'] = 1
                 env['LINGUAS_FILE'] = 1
                 env['POTDOMAIN'] = 'foo'
                 env.POUpdate()

       Program(), env.Program()
           Builds an executable given one or more object files or C, C++, D,
           or Fortran source files. If any C, C++, D or Fortran source files
           are specified, then they will be automatically compiled to object
           files using the Object builder method; see that builder method's
           description for a list of legal source file suffixes and how they
           are interpreted. The target executable file prefix, specified by
           the $PROGPREFIX construction variable (nothing by default), and
           suffix, specified by the $PROGSUFFIX construction variable (by
           default, .exe on Windows systems, nothing on POSIX systems), are
           automatically added to the target if not already present. Example:

               env.Program(target='foo', source=['foo.o', 'bar.c', 'baz.f'])

       ProgramAllAtOnce(), env.ProgramAllAtOnce()
           Builds an executable from D sources without first creating
           individual objects for each file.

           D sources can be compiled file-by-file as C and C++ source are, and
           D is integrated into the scons Object and Program builders for this
           model of build. D codes can though do whole source meta-programming
           (some of the testing frameworks do this). For this it is imperative
           that all sources are compiled and linked in a single call to the D
           compiler. This builder serves that purpose.

                   env.ProgramAllAtOnce('executable', ['mod_a.d, mod_b.d', 'mod_c.d'])


           This command will compile the modules mod_a, mod_b, and mod_c in a
           single compilation process without first creating object files for
           the modules. Some of the D compilers will create executable.o
           others will not.

       RES(), env.RES()
           Builds a Microsoft Visual C++ resource file. This builder method is
           only provided when Microsoft Visual C++ or MinGW is being used as
           the compiler. The .res (or .o for MinGW) suffix is added to the
           target name if no other suffix is given. The source file is scanned
           for implicit dependencies as though it were a C file. Example:

               env.RES('resource.rc')

       RMIC(), env.RMIC()
           Builds stub and skeleton class files for remote objects from Java
           .class files. The target is a directory relative to which the stub
           and skeleton class files will be written. The source can be the
           names of .class files, or the objects return from the Java builder
           method.

           If the construction variable $JAVACLASSDIR is set, either in the
           environment or in the call to the RMIC builder method itself, then
           the value of the variable will be stripped from the beginning of
           any .class file names.

               classes = env.Java(target = 'classdir', source = 'src')
               env.RMIC(target = 'outdir1', source = classes)

               env.RMIC(target = 'outdir2',
                        source = ['package/foo.class', 'package/bar.class'])

               env.RMIC(target = 'outdir3',
                        source = ['classes/foo.class', 'classes/bar.class'],
                        JAVACLASSDIR = 'classes')

       RPCGenClient(), env.RPCGenClient()
           Generates an RPC client stub (_clnt.c) file from a specified RPC
           (.x) source file. Because rpcgen only builds output files in the
           local directory, the command will be executed in the source file's
           directory by default.

               # Builds src/rpcif_clnt.c
               env.RPCGenClient('src/rpcif.x')

       RPCGenHeader(), env.RPCGenHeader()
           Generates an RPC header (.h) file from a specified RPC (.x) source
           file. Because rpcgen only builds output files in the local
           directory, the command will be executed in the source file's
           directory by default.

               # Builds src/rpcif.h
               env.RPCGenHeader('src/rpcif.x')

       RPCGenService(), env.RPCGenService()
           Generates an RPC server-skeleton (_svc.c) file from a specified RPC
           (.x) source file. Because rpcgen only builds output files in the
           local directory, the command will be executed in the source file's
           directory by default.

               # Builds src/rpcif_svc.c
               env.RPCGenClient('src/rpcif.x')

       RPCGenXDR(), env.RPCGenXDR()
           Generates an RPC XDR routine (_xdr.c) file from a specified RPC
           (.x) source file. Because rpcgen only builds output files in the
           local directory, the command will be executed in the source file's
           directory by default.

               # Builds src/rpcif_xdr.c
               env.RPCGenClient('src/rpcif.x')

       SharedLibrary(), env.SharedLibrary()
           Builds a shared library (.so on a POSIX system, .dll on Windows)
           given one or more object files or C, C++, D or Fortran source
           files. If any source files are given, then they will be
           automatically compiled to object files. The target library file
           prefix, specified by the $SHLIBPREFIX construction variable (by
           default, lib on POSIX systems, nothing on Windows systems), and
           suffix, specified by the $SHLIBSUFFIX construction variable (by
           default, .dll on Windows systems, .so on POSIX systems), are
           automatically added to the target if not already present. Example:

               env.SharedLibrary(target='bar', source=['bar.c', 'foo.o'])

           On Windows systems, the SharedLibrary builder method will always
           build an import library (.lib) in addition to the shared library
           (.dll), adding a .lib library with the same basename if there is
           not already a .lib file explicitly listed in the targets.

           On Cygwin systems, the SharedLibrary builder method will always
           build an import library (.dll.a) in addition to the shared library
           (.dll), adding a .dll.a library with the same basename if there is
           not already a .dll.a file explicitly listed in the targets.

           Any object files listed in the source must have been built for a
           shared library (that is, using the SharedObject builder method).
           scons will raise an error if there is any mismatch.

           On some platforms, there is a distinction between a shared library
           (loaded automatically by the system to resolve external references)
           and a loadable module (explicitly loaded by user action). For
           maximum portability, use the LoadableModule builder for the latter.

           When the $SHLIBVERSION construction variable is defined, a
           versioned shared library is created. This modifies $SHLINKFLAGS as
           required, adds the version number to the library name, and creates
           any symbolic links that are needed.

               env.SharedLibrary(target='bar', source=['bar.c', 'foo.o'], SHLIBVERSION='1.5.2')

           On a POSIX system, versions with a single token create exactly one
           symlink: libbar.so.6 would have symlink libbar.so only. On a POSIX
           system, versions with two or more tokens create exactly two
           symlinks: libbar.so.2.3.1 would have symlinks libbar.so and
           libbar.so.2; on a Darwin (OSX) system the library would be
           libbar.2.3.1.dylib and the link would be libbar.dylib.

           On Windows systems, specifying register=1 will cause the .dll to be
           registered after it is built. The command that is run is determined
           by the $REGSVR construction variable (regsvr32 by default), and the
           flags passed are determined by $REGSVRFLAGS. By default,
           $REGSVRFLAGS includes the /s option, to prevent dialogs from
           popping up and requiring user attention when it is run. If you
           change $REGSVRFLAGS, be sure to include the /s option. For example,

               env.SharedLibrary(target='bar', source=['bar.cxx', 'foo.obj'], register=1)

           will register bar.dll as a COM object when it is done linking it.

       SharedObject(), env.SharedObject()
           Builds an object file intended for inclusion in a shared library.
           Source files must have one of the same set of extensions specified
           above for the StaticObject builder method. On some platforms
           building a shared object requires additional compiler option (e.g.
           -fPIC for gcc) in addition to those needed to build a normal
           (static) object, but on some platforms there is no difference
           between a shared object and a normal (static) one. When there is a
           difference, SCons will only allow shared objects to be linked into
           a shared library, and will use a different suffix for shared
           objects. On platforms where there is no difference, SCons will
           allow both normal (static) and shared objects to be linked into a
           shared library, and will use the same suffix for shared and normal
           (static) objects. The target object file prefix, specified by the
           $SHOBJPREFIX construction variable (by default, the same as
           $OBJPREFIX), and suffix, specified by the $SHOBJSUFFIX construction
           variable, are automatically added to the target if not already
           present. Examples:

               env.SharedObject(target='ddd', source='ddd.c')
               env.SharedObject(target='eee.o', source='eee.cpp')
               env.SharedObject(target='fff.obj', source='fff.for')

           Note that the source files will be scanned according to the suffix
           mappings in the SourceFileScanner object. See the manpage section
           "Scanner Objects" for more information.

       StaticLibrary(), env.StaticLibrary()
           Builds a static library given one or more object files or C, C++, D
           or Fortran source files. If any source files are given, then they
           will be automatically compiled to object files. The static library
           file prefix, specified by the $LIBPREFIX construction variable (by
           default, lib on POSIX systems, nothing on Windows systems), and
           suffix, specified by the $LIBSUFFIX construction variable (by
           default, .lib on Windows systems, .a on POSIX systems), are
           automatically added to the target if not already present. Example:

               env.StaticLibrary(target='bar', source=['bar.c', 'foo.o'])

           Any object files listed in the source must have been built for a
           static library (that is, using the StaticObject builder method).
           scons will raise an error if there is any mismatch.

       StaticObject(), env.StaticObject()
           Builds a static object file from one or more C, C++, D, or Fortran
           source files. Source files must have one of the following
           extensions:

                 .asm    assembly language file
                 .ASM    assembly language file
                 .c      C file
                 .C      Windows:  C file
                         POSIX:  C++ file
                 .cc     C++ file
                 .cpp    C++ file
                 .cxx    C++ file
                 .cxx    C++ file
                 .c++    C++ file
                 .C++    C++ file
                 .d      D file
                 .f      Fortran file
                 .F      Windows:  Fortran file
                         POSIX:  Fortran file + C pre-processor
                 .for    Fortran file
                 .FOR    Fortran file
                 .fpp    Fortran file + C pre-processor
                 .FPP    Fortran file + C pre-processor
                 .m      Object C file
                 .mm     Object C++ file
                 .s      assembly language file
                 .S      Windows:  assembly language file
                         ARM: CodeSourcery Sourcery Lite
                 .sx     assembly language file + C pre-processor
                         POSIX:  assembly language file + C pre-processor
                 .spp    assembly language file + C pre-processor
                 .SPP    assembly language file + C pre-processor

           The target object file prefix, specified by the $OBJPREFIX
           construction variable (nothing by default), and suffix, specified
           by the $OBJSUFFIX construction variable (.obj on Windows systems,
           .o on POSIX systems), are automatically added to the target if not
           already present. Examples:

               env.StaticObject(target='aaa', source='aaa.c')
               env.StaticObject(target='bbb.o', source='bbb.c++')
               env.StaticObject(target='ccc.obj', source='ccc.f')

           Note that the source files will be scanned according to the suffix
           mappings in the SourceFileScanner object. See the manpage section
           "Scanner Objects" for more information.

       Substfile(), env.Substfile()
           The Substfile builder creates a single text file from a template
           consisting of a file or set of files (or nodes), replacing text
           using the $SUBST_DICT construction variable (if set). If a set,
           they are concatenated into the target file using the value of the
           $LINESEPARATOR construction variable as a separator between
           contents; the separator is not emitted after the contents of the
           last file. Nested lists of source files are flattened. See also
           Textfile.

           If a single source file name is specified and has a .in suffix, the
           suffix is stripped and the remainder of the name is used as the
           default target name.

           The prefix and suffix specified by the $SUBSTFILEPREFIX and
           $SUBSTFILESUFFIX construction variables (an empty string by default
           in both cases) are automatically added to the target if they are
           not already present.

           If a construction variable named $SUBST_DICT is present, it may be
           either a Python dictionary or a sequence of (key, value) tuples. If
           it is a dictionary it is converted into a list of tuples with
           unspecified order, so if one key is a prefix of another key or if
           one substitution could be further expanded by another subsitition,
           it is unpredictable whether the expansion will occur.

           Any occurrences of a key in the source are replaced by the
           corresponding value, which may be a Python callable function or a
           string. If the value is a callable, it is called with no arguments
           to get a string. Strings are subst-expanded and the result replaces
           the key.

               env = Environment(tools=['default'])

               env['prefix'] = '/usr/bin'
               script_dict = {'@prefix@': '/bin', '@exec_prefix@': '$prefix'}
               env.Substfile('script.in', SUBST_DICT=script_dict)

               conf_dict = {'%VERSION%': '1.2.3', '%BASE%': 'MyProg'}
               env.Substfile('config.h.in', conf_dict, SUBST_DICT=conf_dict)

               # UNPREDICTABLE - one key is a prefix of another
               bad_foo = {'$foo': '$foo', '$foobar': '$foobar'}
               env.Substfile('foo.in', SUBST_DICT=bad_foo)

               # PREDICTABLE - keys are applied longest first
               good_foo = [('$foobar', '$foobar'), ('$foo', '$foo')]
               env.Substfile('foo.in', SUBST_DICT=good_foo)

               # UNPREDICTABLE - one substitution could be futher expanded
               bad_bar = {'@bar@': '@soap@', '@soap@': 'lye'}
               env.Substfile('bar.in', SUBST_DICT=bad_bar)

               # PREDICTABLE - substitutions are expanded in order
               good_bar = (('@bar@', '@soap@'), ('@soap@', 'lye'))
               env.Substfile('bar.in', SUBST_DICT=good_bar)

               # the SUBST_DICT may be in common (and not an override)
               substutions = {}
               subst = Environment(tools=['textfile'], SUBST_DICT=substitutions)
               substitutions['@foo@'] = 'foo'
               subst['SUBST_DICT']['@bar@'] = 'bar'
               subst.Substfile(
                   'pgm1.c',
                   [Value('#include "@foo@.h"'), Value('#include "@bar@.h"'), "common.in", "pgm1.in"],
               )
               subst.Substfile(
                   'pgm2.c',
                   [Value('#include "@foo@.h"'), Value('#include "@bar@.h"'), "common.in", "pgm2.in"],
               )


       Tar(), env.Tar()
           Builds a tar archive of the specified files and/or directories.
           Unlike most builder methods, the Tar builder method may be called
           multiple times for a given target; each additional call adds to the
           list of entries that will be built into the archive. Any source
           directories will be scanned for changes to any on-disk files,
           regardless of whether or not scons knows about them from other
           Builder or function calls.

               env.Tar('src.tar', 'src')

               # Create the stuff.tar file.
               env.Tar('stuff', ['subdir1', 'subdir2'])
               # Also add "another" to the stuff.tar file.
               env.Tar('stuff', 'another')

               # Set TARFLAGS to create a gzip-filtered archive.
               env = Environment(TARFLAGS = '-c -z')
               env.Tar('foo.tar.gz', 'foo')

               # Also set the suffix to .tgz.
               env = Environment(TARFLAGS = '-c -z',
                                 TARSUFFIX = '.tgz')
               env.Tar('foo')

       Textfile(), env.Textfile()
           The Textfile builder generates a single text file from a template
           consisting of a list of strings, replacing text using the
           $SUBST_DICT construction variable (if set) - see Substfile for a
           description of replacement. The strings will be separated in the
           target file using the value of the $LINESEPARATOR construction
           variable; the line separator is not emitted after the last string.
           Nested lists of source strings are flattened. Source strings need
           not literally be Python strings: they can be Nodes or Python
           objects that convert cleanly to Value nodes

           The prefix and suffix specified by the $TEXTFILEPREFIX and
           $TEXTFILESUFFIX construction variables (by default an empty string
           and .txt, respectively) are automatically added to the target if
           they are not already present. Examples:

               # builds/writes foo.txt
               env.Textfile(target='foo.txt', source=['Goethe', 42, 'Schiller'])

               # builds/writes bar.txt
               env.Textfile(target='bar', source=['lalala', 'tanteratei'], LINESEPARATOR='|*')

               # nested lists are flattened automatically
               env.Textfile(target='blob', source=['lalala', ['Goethe', 42, 'Schiller'], 'tanteratei'])

               # files may be used as input by wraping them in File()
               env.Textfile(
                   target='concat',  # concatenate files with a marker between
                   source=[File('concat1'), File('concat2')],
                   LINESEPARATOR='====================\n',
               )

           Results:

           foo.txt

                 Goethe
                 42
                 Schiller

           bar.txt

                 lalala|*tanteratei

           blob.txt

                 lalala
                 Goethe
                 42
                 Schiller
                 tanteratei

       Translate(), env.Translate()
           This pseudo-builder belongs to gettext toolset. The builder
           extracts internationalized messages from source files, updates POT
           template (if necessary) and then updates PO translations (if
           necessary). If $POAUTOINIT is set, missing PO files will be
           automatically created (i.e. without translator person
           intervention). The variables $LINGUAS_FILE and $POTDOMAIN are taken
           into acount too. All other construction variables used by
           POTUpdate, and POUpdate work here too.


           Example 1. The simplest way is to specify input files and output
           languages inline in a SCons script when invoking Translate

               # SConscript in 'po/' directory
               env = Environment( tools = ["default", "gettext"] )
               env['POAUTOINIT'] = 1
               env.Translate(['en','pl'], ['../a.cpp','../b.cpp'])


           Example 2. If you wish, you may also stick to conventional style
           known from autotools, i.e. using POTFILES.in and LINGUAS files

               # LINGUAS
               en pl
               #end

               # POTFILES.in
               a.cpp
               b.cpp
               # end

               # SConscript
               env = Environment( tools = ["default", "gettext"] )
               env['POAUTOINIT'] = 1
               env['XGETTEXTPATH'] = ['../']
               env.Translate(LINGUAS_FILE = 1, XGETTEXTFROM = 'POTFILES.in')

           The last approach is perhaps the recommended one. It allows easily
           split internationalization/localization onto separate SCons
           scripts, where a script in source tree is responsible for
           translations (from sources to PO files) and script(s) under variant
           directories are responsible for compilation of PO to MO files to
           and for installation of MO files. The "gluing factor" synchronizing
           these two scripts is then the content of LINGUAS file. Note, that
           the updated POT and PO files are usually going to be committed back
           to the repository, so they must be updated within the source
           directory (and not in variant directories). Additionaly, the file
           listing of po/ directory contains LINGUAS file, so the source tree
           looks familiar to translators, and they may work with the project
           in their usual way.


           Example 3. Let's prepare a development tree as below

                project/
                 + SConstruct
                 + build/
                 + src/
                     + po/
                         + SConscript
                         + SConscript.i18n
                         + POTFILES.in
                         + LINGUAS

           with build being variant directory. Write the top-level SConstruct
           script as follows

                 # SConstruct
                 env = Environment( tools = ["default", "gettext"] )
                 VariantDir('build', 'src', duplicate = 0)
                 env['POAUTOINIT'] = 1
                 SConscript('src/po/SConscript.i18n', exports = 'env')
                 SConscript('build/po/SConscript', exports = 'env')

           the src/po/SConscript.i18n as

                 # src/po/SConscript.i18n
                 Import('env')
                 env.Translate(LINGUAS_FILE=1, XGETTEXTFROM='POTFILES.in', XGETTEXTPATH=['../'])

           and the src/po/SConscript

                 # src/po/SConscript
                 Import('env')
                 env.MOFiles(LINGUAS_FILE = 1)

           Such setup produces POT and PO files under source tree in src/po/
           and binary MO files under variant tree in build/po/. This way the
           POT and PO files are separated from other output files, which must
           not be committed back to source repositories (e.g.  MO files).


               Note
               In above example, the PO files are not updated, nor created
               automatically when you issue scons '.' command. The files must
               be updated (created) by hand via scons po-update and then MO
               files can be compiled by running scons '.'.

       TypeLibrary(), env.TypeLibrary()
           Builds a Windows type library (.tlb) file from an input IDL file
           (.idl). In addition, it will build the associated interface stub
           and proxy source files, naming them according to the base name of
           the .idl file. For example,

               env.TypeLibrary(source="foo.idl")

           Will create foo.tlb, foo.h, foo_i.c, foo_p.c and foo_data.c files.

       Uic(), env.Uic()
           Builds a header file, an implementation file and a moc file from an
           ui file. and returns the corresponding nodes in the above order.
           This builder is only available after using the tool 'qt'. Note: you
           can specify .ui files directly as source files to the Program,
           Library and SharedLibrary builders without using this builder.
           Using this builder lets you override the standard naming
           conventions (be careful: prefixes are always prepended to names of
           built files; if you don't want prefixes, you may set them to ``).
           See the $QTDIR variable for more information. Example:

               env.Uic('foo.ui') # -> ['foo.h', 'uic_foo.cc', 'moc_foo.cc']
               env.Uic(target = Split('include/foo.h gen/uicfoo.cc gen/mocfoo.cc'),
                       source = 'foo.ui') # -> ['include/foo.h', 'gen/uicfoo.cc', 'gen/mocfoo.cc']

       Zip(), env.Zip()
           Builds a zip archive of the specified files and/or directories.
           Unlike most builder methods, the Zip builder method may be called
           multiple times for a given target; each additional call adds to the
           list of entries that will be built into the archive. Any source
           directories will be scanned for changes to any on-disk files,
           regardless of whether or not scons knows about them from other
           Builder or function calls.

               env.Zip('src.zip', 'src')

               # Create the stuff.zip file.
               env.Zip('stuff', ['subdir1', 'subdir2'])
               # Also add "another" to the stuff.tar file.
               env.Zip('stuff', 'another')

       All targets of builder methods automatically depend on their sources.
       An explicit dependency can be specified using the env.Depends method of
       a construction environment (see below).

       In addition, scons automatically scans source files for various
       programming languages, so the dependencies do not need to be specified
       explicitly. By default, SCons can C source files, C++ source files,
       Fortran source files with .F (POSIX systems only), .fpp, or .FPP file
       extensions, and assembly language files with .S (POSIX systems only),
       .spp, or .SPP files extensions for C preprocessor dependencies. SCons
       also has default support for scanning D source files, You can also
       write your own Scanners to add support for additional source file
       types. These can be added to the default Scanner object used by the
       Object, StaticObject and SharedObject Builders by adding them to the
       SourceFileScanner object. See the section called "Scanner Objects" for
       more information about defining your own Scanner objects and using the
       SourceFileScanner object.

   Methods and Functions To Do Things
       In addition to Builder methods, scons provides a number of other
       construction environment methods and global functions to manipulate the
       build configuration.

       Usually, a construction environment method and global function with the
       same name both exist for convenience. In the following list, the global
       function is documented in this style:

           Function(arguments, [optional arguments])

       and the construction environment method looks like:

           env.Function(arguments, [optional arguments])

       If the function can be called both ways, then both forms are listed.

       The global function and same-named construction environment method
       provide almost identical functionality, with a couple of exceptions.
       First, many of the construction environment methods affect only that
       construction environment, while the global function has a global
       effect. Second, where appropriate, calling the functionality through a
       construction environment will substitute construction variables into
       any supplied string arguments, while the global function doesn't have
       the context of a construction environment to pick variables from, so it
       cannot perform the substitution. For example:

           Default('$FOO')

           env = Environment(FOO='foo')
           env.Default('$FOO')

       In the above example, the call to the global Default function will add
       a target named $FOO to the list of default targets, while the call to
       the env.Default construction environment method will expand the value
       and add a target named foo to the list of default targets. For more on
       construction variable expansion, see the next section on construction
       variables.

       Global functions may be called from custom Python modules that you
       import into an SConscript file by adding the following import to the
       Python module:

           from SCons.Script import *

       Construction environment methods and global functions provided by scons
       include:

       Action(action, [output, [var, ...]] [key=value, ...]),
       env.Action(action, [output, [var, ...]] [key=value, ...])
           A factory function to create an Action object for the specified
           action. See the manpage section "Action Objects" for a complete
           explanation of the arguments and behavior.

           Note that the env.Action form of the invocation will expand
           construction variables in any argument strings, including the
           action argument, at the time it is called using the construction
           variables in the env construction environment through which
           env.Action was called. The Action global function form delays all
           variable expansion until the Action object is actually used.

       AddMethod(object, function, [name]), env.AddMethod(function, [name])
           Adds function to an object as a method.  function will be called
           with an instance object as the first argument as for other methods.
           If name is given, it is used as the name of the new method, else
           the name of function is used.

           When the global function AddMethod is called, the object to add the
           method to must be passed as the first argument; typically this will
           be Environment, in order to create a method which applies to all
           construction environments subsequently constructed. When called
           using the env.AddMethod form, the method is added to the specified
           construction environment only. Added methods propagate through
           env.Clone calls.

           Examples:

               # Function to add must accept an instance argument.
               # The Python convention is to call this 'self'.
               def my_method(self, arg):
                   print("my_method() got", arg)

               # Use the global function to add a method to the Environment class:
               AddMethod(Environment, my_method)
               env = Environment()
               env.my_method('arg')

               # Use the optional name argument to set the name of the method:
               env.AddMethod(my_method, 'other_method_name')
               env.other_method_name('another arg')

       AddOption(arguments)
           Adds a local (project-specific) command-line option.  arguments are
           the same as those supported by the add_option method in the
           standard Python library module optparse, with a few additional
           capabilities noted below. See the documentation for optparse for a
           thorough discussion of its option-processing capabities.

           In addition to the arguments and values supported by the optparse
           add_option method, AddOption allows setting the nargs keyword value
           to a string consisting of a question mark ('?') to indicate that
           the option argument for that option string is optional. If the
           option string is present on the command line but has no matching
           option argument, the value of the const keyword argument is
           produced as the value of the option. If the option string is
           omitted from the command line, the value of the default keyword
           argument is produced, as usual; if there is no default keyword
           argument in the AddOption call, None is produced.


           optparse recognizes abbreviations of long option names, as long as
           they can be unambiguously resolved. For example, if add_option is
           called to define a --devicename option, it will recognize --device,
           --dev and so forth as long as there is no other option which could
           also match to the same abbreviation. Options added via AddOption do
           not support the automatic recognition of abbreviations. Instead, to
           allow specific abbreviations, include them as synonyms in the
           AddOption call itself.

           Once a new command-line option has been added with AddOption, the
           option value may be accessed using GetOption or env.GetOption.
           SetOption is not currently supported for options added with
           AddOption.

           Help text for an option is a combination of the string supplied in
           the help keyword argument to AddOption and information collected
           from the other keyword arguments. Such help is displayed if the -h
           command line option is used (but not with -H). Help for all local
           options is displayed under the separate heading Local Options. The
           options are unsorted - they will appear in the help text in the
           order in which the AddOption calls occur.

           Example:

               AddOption(
                   '--prefix',
                   dest='prefix',
                   nargs=1,
                   type='string',
                   action='store',
                   metavar='DIR',
                   help='installation prefix',
               )
               env = Environment(PREFIX=GetOption('prefix'))

           For that example, the following help text would be produced:

               Local Options:
                 --prefix=DIR                installation prefix

           Help text for local options may be unavailable if the Help function
           has been called, see the Help documentation for details.

               Note
               As an artifact of the internal implementation, the behavior of
               options added by AddOption which take option arguments is
               undefined if whitespace (rather than an = sign) is used as the
               separator on the command line. Users should avoid such usage;
               it is recommended to add a note to this effect to project
               documentation if the situation is likely to arise. In addition,
               if the nargs keyword is used to specify more than one following
               option argument (that is, with a value of 2 or greater), such
               arguments would necessarily be whitespace separated, triggering
               the issue. Developers should not use AddOption this way. Future
               versions of SCons will likely forbid such usage.

       AddPostAction(target, action), env.AddPostAction(target, action)
           Arranges for the specified action to be performed after the
           specified target has been built. The specified action(s) may be an
           Action object, or anything that can be converted into an Action
           object See the manpage section "Action Objects" for a complete
           explanation.

           When multiple targets are supplied, the action may be called
           multiple times, once after each action that generates one or more
           targets in the list.

       AddPreAction(target, action), env.AddPreAction(target, action)
           Arranges for the specified action to be performed before the
           specified target is built. The specified action(s) may be an Action
           object, or anything that can be converted into an Action object See
           the manpage section "Action Objects" for a complete explanation.

           When multiple targets are specified, the action(s) may be called
           multiple times, once before each action that generates one or more
           targets in the list.

           Note that if any of the targets are built in multiple steps, the
           action will be invoked just before the "final" action that
           specifically generates the specified target(s). For example, when
           building an executable program from a specified source .c file via
           an intermediate object file:

               foo = Program('foo.c')
               AddPreAction(foo, 'pre_action')

           The specified pre_action would be executed before scons calls the
           link command that actually generates the executable program binary
           foo, not before compiling the foo.c file into an object file.

       Alias(alias, [targets, [action]]), env.Alias(alias, [targets,
       [action]])
           Creates one or more phony targets that expand to one or more other
           targets. An optional action (command) or list of actions can be
           specified that will be executed whenever the any of the alias
           targets are out-of-date. Returns the Node object representing the
           alias, which exists outside of any file system. This Node object,
           or the alias name, may be used as a dependency of any other target,
           including another alias.  Alias can be called multiple times for
           the same alias to add additional targets to the alias, or
           additional actions to the list for this alias. Aliases are global
           even if set through the construction environment method.

           Examples:

               Alias('install')
               Alias('install', '/usr/bin')
               Alias(['install', 'install-lib'], '/usr/local/lib')

               env.Alias('install', ['/usr/local/bin', '/usr/local/lib'])
               env.Alias('install', ['/usr/local/man'])

               env.Alias('update', ['file1', 'file2'], "update_database $SOURCES")

       AllowSubstExceptions([exception, ...])
           Specifies the exceptions that will be allowed when expanding
           construction variables. By default, any construction variable
           expansions that generate a NameError or IndexError exception will
           expand to a '' (an empty string) and not cause scons to fail. All
           exceptions not in the specified list will generate an error message
           and terminate processing.

           If AllowSubstExceptions is called multiple times, each call
           completely overwrites the previous list of allowed exceptions.

           Example:

               # Requires that all construction variable names exist.
               # (You may wish to do this if you want to enforce strictly
               # that all construction variables must be defined before use.)
               AllowSubstExceptions()

               # Also allow a string containing a zero-division expansion
               # like '${1 / 0}' to evalute to ''.
               AllowSubstExceptions(IndexError, NameError, ZeroDivisionError)

       AlwaysBuild(target, ...), env.AlwaysBuild(target, ...)
           Marks each given target so that it is always assumed to be out of
           date, and will always be rebuilt if needed. Note, however, that
           AlwaysBuild does not add its target(s) to the default target list,
           so the targets will only be built if they are specified on the
           command line, or are a dependent of a target specified on the
           command line--but they will always be built if so specified.
           Multiple targets can be passed in to a single call to AlwaysBuild.

       env.Append(key=val, [...])
           Intelligently append values to construction variables in the
           construction environment named by env. The construction variables
           and values to add to them are passed as key=val pairs (Python
           keyword arguments).  env.Append is designed to allow adding values
           without normally having to know the data type of an existing
           construction variable. Regular Python syntax can also be used to
           manipulate the construction variable, but for that you must know
           the type of the construction variable: for example, different
           Python syntax is needed to combine a list of values with a single
           string value, or vice versa. Some pre-defined construction
           variables do have type expectations based on how SCons will use
           them, for example $CPPDEFINES is normally a string or a list of
           strings, but can be a string, a list of strings, a list of tuples,
           or a dictionary, while $LIBEMITTER would expect a callable or list
           of callables, and $BUILDERS would expect a mapping type. Consult
           the documentation for the various construction variables for more
           details.

           The following descriptions apply to both the append and prepend
           functions, the only difference being the insertion point of the
           added values.

           If env. does not have a construction variable indicated by key, val
           is added to the environment under that key as-is.


           val can be almost any type, and SCons will combine it with an
           existing value into an appropriate type, but there are a few
           special cases to be aware of. When two strings are combined, the
           result is normally a new string, with the caller responsible for
           supplying any needed separation. The exception to this is the
           construction variable $CPPDEFINES, in which each item will be
           postprocessed by adding a prefix and/or suffix, so the contents are
           treated as a list of strings, that is, adding a string will result
           in a separate string entry, not a combined string. For $CPPDEFINES
           as well as for $LIBS, and the various *PATH variables, SCons will
           supply the compiler-specific syntax (e.g. adding a -D or /D prefix
           for $CPPDEFINES), so this syntax should be omitted when adding
           values to these variables. Example (gcc syntax shown in the
           expansion of CPPDEFINES):

               env = Environment(CXXFLAGS="-std=c11", CPPDEFINES="RELEASE")
               print("CXXFLAGS={}, CPPDEFINES={}".format(env['CXXFLAGS'], env['CPPDEFINES']))
               # notice including a leading space in CXXFLAGS value
               env.Append(CXXFLAGS=" -O", CPPDEFINES="EXTRA")
               print("CXXFLAGS={}, CPPDEFINES={}".format(env['CXXFLAGS'], env['CPPDEFINES']))
               print("CPPDEFINES will expand to {}".format(env.subst("$_CPPDEFFLAGS")))

               $ scons -Q
               CXXFLAGS=-std=c11, CPPDEFINES=RELEASE
               CXXFLAGS=-std=c11 -O, CPPDEFINES=['RELEASE', 'EXTRA']
               CPPDEFINES will expand to -DRELEASE -DEXTRA
               scons: `.' is up to date.

           Because $CPPDEFINES is intended to describe C/C++ pre-processor
           macro definitions, it accepts additional syntax. Preprocessor
           macros can be valued, or un-valued, as in -DBAR=1 or -DFOO. The
           macro can be be supplied as a complete string including the value,
           or as a tuple (or list) of macro, value, or as a dictionary.
           Example (again gcc syntax in the expanded defines):

               env = Environment(CPPDEFINES="FOO")
               print("CPPDEFINES={}".format(env['CPPDEFINES']))
               env.Append(CPPDEFINES="BAR=1")
               print("CPPDEFINES={}".format(env['CPPDEFINES']))
               env.Append(CPPDEFINES=("OTHER", 2))
               print("CPPDEFINES={}".format(env['CPPDEFINES']))
               env.Append(CPPDEFINES={"EXTRA": "arg"})
               print("CPPDEFINES={}".format(env['CPPDEFINES']))
               print("CPPDEFINES will expand to {}".format(env.subst("$_CPPDEFFLAGS")))

               $ scons -Q
               CPPDEFINES=FOO
               CPPDEFINES=['FOO', 'BAR=1']
               CPPDEFINES=['FOO', 'BAR=1', ('OTHER', 2)]
               CPPDEFINES=['FOO', 'BAR=1', ('OTHER', 2), {'EXTRA': 'arg'}]
               CPPDEFINES will expand to -DFOO -DBAR=1 -DOTHER=2 -DEXTRA=arg
               scons: `.' is up to date.

           Adding a string val to a dictonary construction variable will enter
           val as the key in the dict, and None as its value. Using a tuple
           type to supply a key + value only works for the special case of
           $CPPDEFINES described above.

           Although most combinations of types work without needing to know
           the details, some combinations do not make sense and a Python
           exception will be raised.

           When using env.Append to modify construction variables which are
           path specifications (normally, those names which end in PATH), it
           is recommended to add the values as a list of strings, even if
           there is only a single string to add. The same goes for adding
           library names to $LIBS.

               env.Append(CPPPATH=["#/include"])

           See also env.AppendUnique, env.Prepend and env.PrependUnique.

       env.AppendENVPath(name, newpath, [envname, sep, delete_existing=False])
           Append new path elements to the given path in the specified
           external environment ($ENV by default). This will only add any
           particular path once (leaving the last one it encounters and
           ignoring the rest, to preserve path order), and to help assure
           this, will normalize all paths (using os.path.normpath and
           os.path.normcase). This can also handle the case where the given
           old path variable is a list instead of a string, in which case a
           list will be returned instead of a string.

           If delete_existing is False, then adding a path that already exists
           will not move it to the end; it will stay where it is in the list.

           Example:

               print('before:', env['ENV']['INCLUDE'])
               include_path = '/foo/bar:/foo'
               env.AppendENVPath('INCLUDE', include_path)
               print('after:', env['ENV']['INCLUDE'])

           Yields:

               before: /foo:/biz
               after: /biz:/foo/bar:/foo

       env.AppendUnique(key=val, [...], delete_existing=False)
           Append values to construction variables in the current construction
           environment, maintaining uniqueness. Works like env.Append (see for
           details), except that values already present in the construction
           variable will not be added again. If delete_existing is True, the
           existing matching value is first removed, and the requested value
           is added, having the effect of moving such values to the end.

           Example:

               env.AppendUnique(CCFLAGS='-g', FOO=['foo.yyy'])

           See also env.Append, env.Prepend and env.PrependUnique.

       Builder(action, [arguments]), env.Builder(action, [arguments])
           Creates a Builder object for the specified action. See the manpage
           section "Builder Objects" for a complete explanation of the
           arguments and behavior.

           Note that the env.Builder() form of the invocation will expand
           construction variables in any arguments strings, including the
           action argument, at the time it is called using the construction
           variables in the env construction environment through which
           env.Builder was called. The Builder form delays all variable
           expansion until after the Builder object is actually called.

       CacheDir(cache_dir, custom_class=None), env.CacheDir(cache_dir,
       custom_class=None)
           Direct scons to maintain a derived-file cache in cache_dir. The
           derived files in the cache will be shared among all the builds
           specifying the same cache_dir. Specifying a cache_dir of None
           disables derived file caching.

           When specifying a custom_class which should be a class type which
           is a subclass of SCons.CacheDir.CacheDir, SCons will internally
           invoke this class to use for performing caching operations. This
           argument is optional and if left to default None, will use the
           default SCons.CacheDir.CacheDir class.

           Calling the environment method env.CacheDir limits the effect to
           targets built through the specified construction environment.
           Calling the global function CacheDir sets a global default that
           will be used by all targets built through construction environments
           that do not set up environment-specific caching by calling
           env.CacheDir.

           When derived-file caching is being used and scons finds a derived
           file that needs to be rebuilt, it will first look in the cache to
           see if a file with matching build signature exists (indicating the
           input file(s) and build action(s) were identical to those for the
           current target), and if so, will retrieve the file from the cache.
           scons will report Retrieved `file' from cache instead of the normal
           build message. If the derived file is not present in the cache,
           scons will build it and then place a copy of the built file in the
           cache, identified by its build signature, for future use.

           The Retrieved `file' from cache messages are useful for human
           consumption, but less so when comparing log files between scons
           runs which will show differences that are noisy and not actually
           significant. To disable, use the --cache-show option. With this
           option, scons will print the action that would have been used to
           build the file without considering cache retrieval.

           Derived-file caching may be disabled for any invocation of scons by
           giving the --cache-disable command line option. Cache updating may
           be disabled, leaving cache fetching enabled, by giving the
           --cache-readonly.

           If the --cache-force option is used, scons will place a copy of all
           derived files in the cache, even if they already existed and were
           not built by this invocation. This is useful to populate a cache
           the first time a cache_dir is used for a build, or to bring a cache
           up to date after a build with cache updating disabled
           (--cache-disable or --cache-readonly) has been done.

           The NoCache method can be used to disable caching of specific
           files. This can be useful if inputs and/or outputs of some tool are
           impossible to predict or prohibitively large.

       Clean(targets, files_or_dirs), env.Clean(targets, files_or_dirs)
           This specifies a list of files or directories which should be
           removed whenever the targets are specified with the -c command line
           option. The specified targets may be a list or an individual
           target. Multiple calls to Clean are legal, and create new targets
           or add files and directories to the clean list for the specified
           targets.

           Multiple files or directories should be specified either as
           separate arguments to the Clean method, or as a list.  Clean will
           also accept the return value of any of the construction environment
           Builder methods. Examples:

           The related NoClean function overrides calling Clean for the same
           target, and any targets passed to both functions will not be
           removed by the -c option.

           Examples:

               Clean('foo', ['bar', 'baz'])
               Clean('dist', env.Program('hello', 'hello.c'))
               Clean(['foo', 'bar'], 'something_else_to_clean')

           In this example, installing the project creates a subdirectory for
           the documentation. This statement causes the subdirectory to be
           removed if the project is deinstalled.

               Clean(docdir, os.path.join(docdir, projectname))

       env.Clone([key=val, ...])
           Returns a separate copy of a construction environment. If there are
           any keyword arguments specified, they are added to the returned
           copy, overwriting any existing values for the keywords.

           Example:

               env2 = env.Clone()
               env3 = env.Clone(CCFLAGS='-g')

           Additionally, a list of tools and a toolpath may be specified, as
           in the Environment constructor:

               def MyTool(env):
                   env['FOO'] = 'bar'

               env4 = env.Clone(tools=['msvc', MyTool])

           The parse_flags keyword argument is also recognized to allow
           merging command-line style arguments into the appropriate
           construction variables (see env.MergeFlags).

               # create an environment for compiling programs that use wxWidgets
               wx_env = env.Clone(parse_flags='!wx-config --cflags --cxxflags')

       Command(target, source, action, [key=val, ...]), env.Command(target,
       source, action, [key=val, ...])
           Executes a specific action (or list of actions) to build a target
           file or files from a source file or files. This is more convenient
           than defining a separate Builder object for a single special-case
           build.

           The Command function accepts source_scanner, target_scanner,
           source_factory, and target_factory keyword arguments. These
           arguments can be used to specify a Scanner object that will be used
           to apply a custom scanner for a source or target. For example, the
           global DirScanner object can be used if any of the sources will be
           directories that must be scanned on-disk for changes to files that
           aren't already specified in other Builder of function calls. The
           *_factory arguments take a factory function that Command will use
           to turn any sources or targets specified as strings into SCons
           Nodes. See the manpage section "Builder Objects" for more
           information about how these arguments work in a Builder.

           Any other keyword arguments specified override any same-named
           existing construction variables.

           An action can be an external command, specified as a string, or a
           callable Python object; see the manpage section "Action Objects"
           for more complete information. Also note that a string specifying
           an external command may be preceded by an at-sign (@) to suppress
           printing the command in question, or by a hyphen (-) to ignore the
           exit status of the external command.

           Examples:

               env.Command(
                   target='foo.out',
                   source='foo.in',
                   action="$FOO_BUILD < $SOURCES > $TARGET"
               )

               env.Command(
                   target='bar.out',
                   source='bar.in',
                   action=["rm -f $TARGET", "$BAR_BUILD < $SOURCES > $TARGET"],
                   ENV={'PATH': '/usr/local/bin/'},
               )


               import os
               def rename(env, target, source):
                   os.rename('.tmp', str(target[0]))


               env.Command(
                   target='baz.out',
                   source='baz.in',
                   action=["$BAZ_BUILD < $SOURCES > .tmp", rename],
               )

           Note that the Command function will usually assume, by default,
           that the specified targets and/or sources are Files, if no other
           part of the configuration identifies what type of entries they are.
           If necessary, you can explicitly specify that targets or source
           nodes should be treated as directories by using the Dir or env.Dir
           functions.

           Examples:

               env.Command('ddd.list', Dir('ddd'), 'ls -l $SOURCE > $TARGET')

               env['DISTDIR'] = 'destination/directory'
               env.Command(env.Dir('$DISTDIR')), None, make_distdir)

           Also note that SCons will usually automatically create any
           directory necessary to hold a target file, so you normally don't
           need to create directories by hand.

       Configure(env, [custom_tests, conf_dir, log_file, config_h]),
       env.Configure([custom_tests, conf_dir, log_file, config_h])
           Creates a Configure object for integrated functionality similar to
           GNU autoconf. See the manpage section "Configure Contexts" for a
           complete explanation of the arguments and behavior.

       Decider(function), env.Decider(function)
           Specifies that all up-to-date decisions for targets built through
           this construction environment will be handled by the specified
           function.  function can be the name of a function or one of the
           following strings that specify the predefined decision function
           that will be applied:

           "timestamp-newer"
               Specifies that a target shall be considered out of date and
               rebuilt if the dependency's timestamp is newer than the target
               file's timestamp. This is the behavior of the classic Make
               utility, and make can be used a synonym for timestamp-newer.

           "timestamp-match"
               Specifies that a target shall be considered out of date and
               rebuilt if the dependency's timestamp is different than the
               timestamp recorded the last time the target was built. This
               provides behavior very similar to the classic Make utility (in
               particular, files are not opened up so that their contents can
               be checksummed) except that the target will also be rebuilt if
               a dependency file has been restored to a version with an
               earlier timestamp, such as can happen when restoring files from
               backup archives.

           "content"
               Specifies that a target shall be considered out of date and
               rebuilt if the dependency's content has changed since the last
               time the target was built, as determined be performing an
               checksum on the dependency's contents and comparing it to the
               checksum recorded the last time the target was built.  MD5 can
               be used as a synonym for content, but it is deprecated.

           "content-timestamp"
               Specifies that a target shall be considered out of date and
               rebuilt if the dependency's content has changed since the last
               time the target was built, except that dependencies with a
               timestamp that matches the last time the target was rebuilt
               will be assumed to be up-to-date and not rebuilt. This provides
               behavior very similar to the content behavior of always
               checksumming file contents, with an optimization of not
               checking the contents of files whose timestamps haven't
               changed. The drawback is that SCons will not detect if a file's
               content has changed but its timestamp is the same, as might
               happen in an automated script that runs a build, updates a
               file, and runs the build again, all within a single second.
               MD5-timestamp can be used as a synonym for content-timestamp,
               but it is deprecated.

           Examples:

               # Use exact timestamp matches by default.
               Decider('timestamp-match')

               # Use hash content signatures for any targets built
               # with the attached construction environment.
               env.Decider('content')

           In addition to the above already-available functions, the function
           argument may be a Python function you supply. Such a function must
           accept the following four arguments:

           dependency
               The Node (file) which should cause the target to be rebuilt if
               it has "changed" since the last tme target was built.

           target
               The Node (file) being built. In the normal case, this is what
               should get rebuilt if the dependency has "changed."

           prev_ni
               Stored information about the state of the dependency the last
               time the target was built. This can be consulted to match
               various file characteristics such as the timestamp, size, or
               content signature.

           repo_node
               If set, use this Node instead of the one specified by
               dependency to determine if the dependency has changed. This
               argument is optional so should be written as a default argument
               (typically it would be written as repo_node=None). A caller
               will normally only set this if the target only exists in a
               Repository.

           The function should return a value which evaluates True if the
           dependency has "changed" since the last time the target was built
           (indicating that the target should be rebuilt), and a value which
           evaluates False otherwise (indicating that the target should not be
           rebuilt). Note that the decision can be made using whatever
           criteria are appopriate. Ignoring some or all of the function
           arguments is perfectly normal.

           Example:

               def my_decider(dependency, target, prev_ni, repo_node=None):
                   return not os.path.exists(str(target))

               env.Decider(my_decider)

       Default(target[, ...]), env.Default(target[, ...])
           Specify default targets to the SCons target selection mechanism.
           Any call to Default will cause SCons to use the defined default
           target list instead of its built-in algorithm for determining
           default targets (see the manpage section "Target Selection").


           target may be one or more strings, a list of strings, a NodeList as
           returned by a Builder, or None. A string target may be the name of
           a file or directory, or a target previously defined by a call to
           Alias (defining the alias later will still create the alias, but it
           will not be recognized as a default). Calls to Default are
           additive. A target of None will clear any existing default target
           list; subsequent calls to Default will add to the (now empty)
           default target list like normal.

           Both forms of this call affect the same global list of default
           targets; the construction environment method applies construction
           variable expansion to the targets.

           The current list of targets added using Default is available in the
           DEFAULT_TARGETS list (see below).

           Examples:

               Default('foo', 'bar', 'baz')
               env.Default(['a', 'b', 'c'])
               hello = env.Program('hello', 'hello.c')
               env.Default(hello)

       DefaultEnvironment([**kwargs])
           Instantiates and returns the default construction environment
           object. The default environment is used internally by SCons in
           order to execute many of the global functions in this list (that
           is, those not called as methods of a specific construction
           environment). It is not mandatory to call DefaultEnvironment: the
           default environment will be instantiated automatically when the
           build phase begins if the function has not been called, however
           calling it explicitly gives the opportunity to affect and examine
           the contents of the default environment.

           The default environment is a singleton, so the keyword arguments
           affect it only on the first call, on subsequent calls the
           already-constructed object is returned and any keyword arguments
           are silently ignored. The default environment can be modified after
           instantiation in the same way as any construction environment.
           Modifying the default environment has no effect on the construction
           environment constructed by an Environment or Clone call.

       Depends(target, dependency), env.Depends(target, dependency)
           Specifies an explicit dependency; the target will be rebuilt
           whenever the dependency has changed. Both the specified target and
           dependency can be a string (usually the path name of a file or
           directory) or Node objects, or a list of strings or Node objects
           (such as returned by a Builder call). This should only be necessary
           for cases where the dependency is not caught by a Scanner for the
           file.

           Example:

               env.Depends('foo', 'other-input-file-for-foo')

               mylib = env.Library('mylib.c')
               installed_lib = env.Install('lib', mylib)
               bar = env.Program('bar.c')

               # Arrange for the library to be copied into the installation
               # directory before trying to build the "bar" program.
               # (Note that this is for example only.  A "real" library
               # dependency would normally be configured through the $LIBS
               # and $LIBPATH variables, not using an env.Depends() call.)

               env.Depends(bar, installed_lib)

       env.Detect(progs)
           Find an executable from one or more choices: progs may be a string
           or a list of strings. Returns the first value from progs that was
           found, or None. Executable is searched by checking the paths
           specified by env['ENV']['PATH']. On Windows systems, additionally
           applies the filename suffixes found in env['ENV']['PATHEXT'] but
           will not include any such extension in the return value.
           env.Detect is a wrapper around env.WhereIs.

       env.Dictionary([vars])
           Returns a dictionary object containing the construction variables
           in the construction environment. If there are any arguments
           specified, the values of the specified construction variables are
           returned as a string (if one argument) or as a list of strings.

           Example:

               cvars = env.Dictionary()
               cc_values = env.Dictionary('CC', 'CCFLAGS', 'CCCOM')

       Dir(name, [directory]), env.Dir(name, [directory])
           Returns Directory Node(s). A Directory Node is an object that
           represents a directory.  name can be a relative or absolute path or
           a list of such paths.  directory is an optional directory that will
           be used as the parent directory. If no directory is specified, the
           current script's directory is used as the parent.

           If name is a single pathname, the corresponding node is returned.
           If name is a list, SCons returns a list of nodes. Construction
           variables are expanded in name.

           Directory Nodes can be used anywhere you would supply a string as a
           directory name to a Builder method or function. Directory Nodes
           have attributes and methods that are useful in many situations; see
           manpage section "File and Directory Nodes" for more information.

       env.Dump([key], [format])
           Serializes construction variables to a string. The method supports
           the following formats specified by format:

           pretty
               Returns a pretty printed representation of the environment (if
               format is not specified, this is the default).

           json
               Returns a JSON-formatted string representation of the
               environment.

           If key is None (the default) the entire dictionary of construction
           variables is serialized. If supplied, it is taken as the name of a
           construction variable whose value is serialized.

           This SConstruct:

               env=Environment()
               print(env.Dump('CCCOM'))

           will print:

               '$CC -c -o $TARGET $CCFLAGS $CPPFLAGS $_CPPDEFFLAGS $_CPPINCFLAGS $SOURCES'

           While this SConstruct:

               env = Environment()
               print(env.Dump())

           will print:

               { 'AR': 'ar',
                 'ARCOM': '$AR $ARFLAGS $TARGET $SOURCES\n$RANLIB $RANLIBFLAGS $TARGET',
                 'ARFLAGS': ['r'],
                 'AS': 'as',
                 'ASCOM': '$AS $ASFLAGS -o $TARGET $SOURCES',
                 'ASFLAGS': [],
                 ...

       EnsurePythonVersion(major, minor), env.EnsurePythonVersion(major,
       minor)
           Ensure that the Python version is at least major.minor. This
           function will print out an error message and exit SCons with a
           non-zero exit code if the actual Python version is not late enough.

           Example:

               EnsurePythonVersion(2,2)

       EnsureSConsVersion(major, minor, [revision]),
       env.EnsureSConsVersion(major, minor, [revision])
           Ensure that the SCons version is at least major.minor, or
           major.minor.revision. if revision is specified. This function will
           print out an error message and exit SCons with a non-zero exit code
           if the actual SCons version is not late enough.

           Examples:

               EnsureSConsVersion(0,14)

               EnsureSConsVersion(0,96,90)

       Environment([key=value, ...]), env.Environment([key=value, ...])
           Return a new construction environment initialized with the
           specified key=value pairs. The keyword arguments parse_flags,
           platform, toolpath, tools and variables are also specially
           recognized. See the manpage section "Construction Environments" for
           more details.

       Execute(action, [strfunction, varlist]), env.Execute(action,
       [strfunction, varlist])
           Executes an Action object. The specified action may be an Action
           object (see manpage section "Action Objects" for an explanation of
           behavior), or it may be a command-line string, list of commands, or
           executable Python function, each of which will be converted into an
           Action object and then executed. Any additional arguments to
           Execute (strfunction, varlist) are passed on to the Action factory
           function which actually creates the Action object. The exit value
           of the command or return value of the Python function will be
           returned.

           Note that scons will print an error message if the executed action
           fails--that is, exits with or returns a non-zero value.  scons will
           not, however, automatically terminate the build if the specified
           action fails. If you want the build to stop in response to a failed
           Execute call, you must explicitly check for a non-zero return
           value:

               Execute(Copy('file.out', 'file.in'))

               if Execute("mkdir sub/dir/ectory"):
                   # The mkdir failed, don't try to build.
                   Exit(1)

       Exit([value]), env.Exit([value])
           This tells scons to exit immediately with the specified value. A
           default exit value of 0 (zero) is used if no value is specified.

       Export([vars...], [key=value...]), env.Export([vars...],
       [key=value...])
           Exports variables from the current SConscript file to a global
           collection where they can be imported by other SConscript files.
           vars may be one or more strings representing variable names to be
           exported. If a string contains whitespace, it is split into
           separate strings, as if multiple string arguments had been given. A
           vars argument may also be a dictionary, which can be used to map
           variables to different names when exported. Keyword arguments can
           be used to provide names and their values.


           Export calls are cumulative. Specifying a previously exported
           variable will overwrite the earlier value. Both local variables and
           global variables can be exported.

           Examples:

               env = Environment()
               # Make env available for all SConscript files to Import().
               Export("env")

               package = 'my_name'
               # Make env and package available for all SConscript files:.
               Export("env", "package")

               # Make env and package available for all SConscript files:
               Export(["env", "package"])

               # Make env available using the name debug:
               Export(debug=env)

               # Make env available using the name debug:
               Export({"debug": env})

           Note that the SConscript function supports an exports argument that
           allows exporting a variable or set of variables to a specific
           SConscript file or files. See the description below.

       File(name, [directory]), env.File(name, [directory])
           Returns File Node(s). A File Node is an object that represents a
           file.  name can be a relative or absolute path or a list of such
           paths.  directory is an optional directory that will be used as the
           parent directory. If no directory is specified, the current
           script's directory is used as the parent.

           If name is a single pathname, the corresponding node is returned.
           If name is a list, SCons returns a list of nodes. Construction
           variables are expanded in name.

           File Nodes can be used anywhere you would supply a string as a file
           name to a Builder method or function. File Nodes have attributes
           and methods that are useful in many situations; see manpage section
           "File and Directory Nodes" for more information.

       FindFile(file, dirs), env.FindFile(file, dirs)
           Search for file in the path specified by dirs.  dirs may be a list
           of directory names or a single directory name. In addition to
           searching for files that exist in the filesystem, this function
           also searches for derived files that have not yet been built.

           Example:

               foo = env.FindFile('foo', ['dir1', 'dir2'])

       FindInstalledFiles(), env.FindInstalledFiles()
           Returns the list of targets set up by the Install or InstallAs
           builders.

           This function serves as a convenient method to select the contents
           of a binary package.

           Example:

               Install('/bin', ['executable_a', 'executable_b'])

               # will return the file node list
               # ['/bin/executable_a', '/bin/executable_b']
               FindInstalledFiles()

               Install('/lib', ['some_library'])

               # will return the file node list
               # ['/bin/executable_a', '/bin/executable_b', '/lib/some_library']
               FindInstalledFiles()

       FindPathDirs(variable)
           Returns a function (actually a callable Python object) intended to
           be used as the path_function of a Scanner object. The returned
           object will look up the specified variable in a construction
           environment and treat the construction variable's value as a list
           of directory paths that should be searched (like $CPPPATH,
           $LIBPATH, etc.).

           Note that use of FindPathDirs is generally preferable to writing
           your own path_function for the following reasons: 1) The returned
           list will contain all appropriate directories found in source trees
           (when VariantDir is used) or in code repositories (when Repository
           or the -Y option are used). 2) scons will identify expansions of
           variable that evaluate to the same list of directories as, in fact,
           the same list, and avoid re-scanning the directories for files,
           when possible.

           Example:

               def my_scan(node, env, path, arg):
                   # Code to scan file contents goes here...
                   return include_files

               scanner = Scanner(name = 'myscanner',
                                 function = my_scan,
                                 path_function = FindPathDirs('MYPATH'))

       FindSourceFiles(node='"."'), env.FindSourceFiles(node='"."')
           Returns the list of nodes which serve as the source of the built
           files. It does so by inspecting the dependency tree starting at the
           optional argument node which defaults to the '"."'-node. It will
           then return all leaves of node. These are all children which have
           no further children.

           This function is a convenient method to select the contents of a
           Source Package.

           Example:

               Program('src/main_a.c')
               Program('src/main_b.c')
               Program('main_c.c')

               # returns ['main_c.c', 'src/main_a.c', 'SConstruct', 'src/main_b.c']
               FindSourceFiles()

               # returns ['src/main_b.c', 'src/main_a.c' ]
               FindSourceFiles('src')

           As you can see build support files (SConstruct in the above
           example) will also be returned by this function.

       Flatten(sequence), env.Flatten(sequence)
           Takes a sequence (that is, a Python list or tuple) that may contain
           nested sequences and returns a flattened list containing all of the
           individual elements in any sequence. This can be helpful for
           collecting the lists returned by calls to Builders; other Builders
           will automatically flatten lists specified as input, but direct
           Python manipulation of these lists does not.

           Examples:

               foo = Object('foo.c')
               bar = Object('bar.c')

               # Because `foo' and `bar' are lists returned by the Object() Builder,
               # `objects' will be a list containing nested lists:
               objects = ['f1.o', foo, 'f2.o', bar, 'f3.o']

               # Passing such a list to another Builder is all right because
               # the Builder will flatten the list automatically:
               Program(source = objects)

               # If you need to manipulate the list directly using Python, you need to
               # call Flatten() yourself, or otherwise handle nested lists:
               for object in Flatten(objects):
                   print(str(object))

       GetBuildFailures()
           Returns a list of exceptions for the actions that failed while
           attempting to build targets. Each element in the returned list is a
           BuildError object with the following attributes that record various
           aspects of the build failure:


           .node The node that was being built when the build failure
           occurred.


           .status The numeric exit status returned by the command or Python
           function that failed when trying to build the specified Node.


           .errstr The SCons error string describing the build failure. (This
           is often a generic message like "Error 2" to indicate that an
           executed command exited with a status of 2.)


           .filename The name of the file or directory that actually caused
           the failure. This may be different from the .node attribute. For
           example, if an attempt to build a target named sub/dir/target fails
           because the sub/dir directory could not be created, then the .node
           attribute will be sub/dir/target but the .filename attribute will
           be sub/dir.


           .executor The SCons Executor object for the target Node being
           built. This can be used to retrieve the construction environment
           used for the failed action.


           .action The actual SCons Action object that failed. This will be
           one specific action out of the possible list of actions that would
           have been executed to build the target.


           .command The actual expanded command that was executed and failed,
           after expansion of $TARGET, $SOURCE, and other construction
           variables.

           Note that the GetBuildFailures function will always return an empty
           list until any build failure has occurred, which means that
           GetBuildFailures will always return an empty list while the
           SConscript files are being read. Its primary intended use is for
           functions that will be executed before SCons exits by passing them
           to the standard Python atexit.register() function. Example:

               import atexit

               def print_build_failures():
                   from SCons.Script import GetBuildFailures
                   for bf in GetBuildFailures():
                       print("%s failed: %s" % (bf.node, bf.errstr))

               atexit.register(print_build_failures)

       GetBuildPath(file, [...]), env.GetBuildPath(file, [...])
           Returns the scons path name (or names) for the specified file (or
           files). The specified file or files may be scons Nodes or strings
           representing path names.

       GetLaunchDir(), env.GetLaunchDir()
           Returns the absolute path name of the directory from which scons
           was initially invoked. This can be useful when using the -u, -U or
           -D options, which internally change to the directory in which the
           SConstruct file is found.

       GetOption(name), env.GetOption(name)
           This function provides a way to query the value of options which
           can be set via the command line or using the SetOption function.


           name can be an entry from the following table, which shows the
           corresponding command line arguments that could affect the value.
           name can be also be the destination variable name from a
           project-specific option added using the AddOption function, as long
           as the addition happens prior to the GetOption call in the
           SConscript files.

           +------------------------+---------------------------+--------------------+
           |Query name              | Command-line              | Notes              |
           |                        | options                   |                    |
           +------------------------+---------------------------+--------------------+
           |cache_debug             | --cache-debug             |                    |
           +------------------------+---------------------------+--------------------+
           |cache_disable           | --cache-disable,          |                    |
           |                        |       --no-cache          |                    |
           +------------------------+---------------------------+--------------------+
           |cache_force             | --cache-force,            |                    |
           |                        |       --cache-populate    |                    |
           +------------------------+---------------------------+--------------------+
           |cache_readonly          | --cache-readonly          |                    |
           +------------------------+---------------------------+--------------------+
           |cache_show              | --cache-show              |                    |
           +------------------------+---------------------------+--------------------+
           |clean                   | -c,                       |                    |
           |                        |       --clean,            |                    |
           |                        |       --remove            |                    |
           +------------------------+---------------------------+--------------------+
           |climb_up                | -D                        |                    |
           |                        |       -U                  |                    |
           |                        |       -u                  |                    |
           |                        |       --up                |                    |
           |                        |       --search_up         |                    |
           +------------------------+---------------------------+--------------------+
           |config                  | --config                  |                    |
           +------------------------+---------------------------+--------------------+
           |debug                   | --debug                   |                    |
           +------------------------+---------------------------+--------------------+
           |directory               | -C, --directory           |                    |
           +------------------------+---------------------------+--------------------+
           |diskcheck               | --diskcheck               |                    |
           +------------------------+---------------------------+--------------------+
           |duplicate               | --duplicate               |                    |
           +------------------------+---------------------------+--------------------+
           |enable_virtualenv       | --enable-virtualenv       |                    |
           +------------------------+---------------------------+--------------------+
           |experimental            | --experimental            | since 4.2          |
           +------------------------+---------------------------+--------------------+
           |file                    | -f,                       |                    |
           |                        |       --file,             |                    |
           |                        |       --makefile,         |                    |
           |                        |       --sconstruct        |                    |
           +------------------------+---------------------------+--------------------+
           |hash_format             | --hash-format             | since 4.2          |
           +------------------------+---------------------------+--------------------+
           |help                    | -h, --help                |                    |
           +------------------------+---------------------------+--------------------+
           |ignore_errors           | -i, --ignore-errors       |                    |
           +------------------------+---------------------------+--------------------+
           |ignore_virtualenv       | --ignore-virtualenv       |                    |
           +------------------------+---------------------------+--------------------+
           |implicit_cache          | --implicit-cache          |                    |
           +------------------------+---------------------------+--------------------+
           |implicit_deps_changed   | --implicit-deps-changed   |                    |
           +------------------------+---------------------------+--------------------+
           |implicit_deps_unchanged | --implicit-deps-unchanged |                    |
           +------------------------+---------------------------+--------------------+
           |include_dir             | -I, --include-dir         |                    |
           +------------------------+---------------------------+--------------------+
           |install_sandbox         | --install-sandbox         | Available only if  |
           |                        |                           | the install tool   |
           |                        |                           | has been called    |
           +------------------------+---------------------------+--------------------+
           |keep_going              | -k, --keep-going          |                    |
           +------------------------+---------------------------+--------------------+
           |max_drift               | --max-drift               |                    |
           +------------------------+---------------------------+--------------------+
           |md5_chunksize           | --hash-chunksize,         | --hash-chunksize   |
           |                        |       --md5-chunksize     | since 4.2          |
           +------------------------+---------------------------+--------------------+
           |no_exec                 | -n,                       |                    |
           |                        |       --no-exec,          |                    |
           |                        |       --just-print,       |                    |
           |                        |       --dry-run,          |                    |
           |                        |       --recon             |                    |
           +------------------------+---------------------------+--------------------+
           |no_progress             | -Q                        |                    |
           +------------------------+---------------------------+--------------------+
           |num_jobs                | -j, --jobs                |                    |
           +------------------------+---------------------------+--------------------+
           |package_type            | --package-type            | Available only if  |
           |                        |                           | the packaging tool |
           |                        |                           | has been called    |
           +------------------------+---------------------------+--------------------+
           |profile_file            | --profile                 |                    |
           +------------------------+---------------------------+--------------------+
           |question                | -q, --question            |                    |
           +------------------------+---------------------------+--------------------+
           |random                  | --random                  |                    |
           +------------------------+---------------------------+--------------------+
           |repository              | -Y,                       |                    |
           |                        |       --repository,       |                    |
           |                        |       --srcdir            |                    |
           +------------------------+---------------------------+--------------------+
           |silent                  | -s,                       |                    |
           |                        |       --silent,           |                    |
           |                        |       --quiet             |                    |
           +------------------------+---------------------------+--------------------+
           |site_dir                | --site-dir, --no-site-dir |                    |
           +------------------------+---------------------------+--------------------+
           |stack_size              | --stack-size              |                    |
           +------------------------+---------------------------+--------------------+
           |taskmastertrace_file    | --taskmastertrace         |                    |
           +------------------------+---------------------------+--------------------+
           |tree_printers           | --tree                    |                    |
           +------------------------+---------------------------+--------------------+
           |warn                    | --warn, --warning         |                    |
           +------------------------+---------------------------+--------------------+
           See the documentation for the corresponding command line option for
           information about each specific option.

       Glob(pattern, [ondisk, source, strings, exclude]), env.Glob(pattern,
       [ondisk, source, strings, exclude])
           Returns Nodes (or strings) that match the specified pattern,
           relative to the directory of the current SConscript file. The
           evironment method form (env.Glob) performs string substition on
           pattern and returns whatever matches the resulting expanded
           pattern.

           The specified pattern uses Unix shell style metacharacters for
           matching:

                 *       matches everything
                 ?       matches any single character
                 [seq]   matches any character in seq
                 [!seq]  matches any char not in seq

           If the first character of a filename is a dot, it must be matched
           explicitly. Character matches do not span directory separators.

           The Glob knows about repositories (see the Repository function) and
           source directories (see the VariantDir function) and returns a Node
           (or string, if so configured) in the local (SConscript) directory
           if a matching Node is found anywhere in a corresponding repository
           or source directory.

           The ondisk argument may be set to a value which evaluates False to
           disable the search for matches on disk, thereby only returning
           matches among already-configured File or Dir Nodes. The default
           behavior is to return corresponding Nodes for any on-disk matches
           found.

           The source argument may be set to a value which evaluates True to
           specify that, when the local directory is a VariantDir, the
           returned Nodes should be from the corresponding source directory,
           not the local directory.

           The strings argument may be set to a value which evaluates True to
           have the Glob function return strings, not Nodes, that represent
           the matched files or directories. The returned strings will be
           relative to the local (SConscript) directory. (Note that This may
           make it easier to perform arbitrary manipulation of file names, but
           if the returned strings are passed to a different SConscript file,
           any Node translation will be relative to the other SConscript
           directory, not the original SConscript directory.)

           The exclude argument may be set to a pattern or a list of patterns
           (following the same Unix shell semantics) which must be filtered
           out of returned elements. Elements matching a least one pattern of
           this list will be excluded.

           Examples:

               Program("foo", Glob("*.c"))
               Zip("/tmp/everything", Glob(".??*") + Glob("*"))
               sources = Glob("*.cpp", exclude=["os_*_specific_*.cpp"]) + \
                         Glob( "os_%s_specific_*.cpp" % currentOS)

       Help(text, append=False), env.Help(text, append=False)
           Specifies a local help message to be printed if the -h argument is
           given to scons. Subsequent calls to Help append text to the
           previously defined local help text.

           For the first call to Help only, if append is False (the default)
           any local help message generated through AddOption calls is
           replaced. If append is True, text is appended to the existing help
           text.

       Ignore(target, dependency), env.Ignore(target, dependency)
           The specified dependency file(s) will be ignored when deciding if
           the target file(s) need to be rebuilt.

           You can also use Ignore to remove a target from the default build.
           In order to do this you must specify the directory the target will
           be built in as the target, and the file you want to skip building
           as the dependency.

           Note that this will only remove the dependencies listed from the
           files built by default. It will still be built if that dependency
           is needed by another object being built. See the third and forth
           examples below.

           Examples:

               env.Ignore('foo', 'foo.c')
               env.Ignore('bar', ['bar1.h', 'bar2.h'])
               env.Ignore('.', 'foobar.obj')
               env.Ignore('bar', 'bar/foobar.obj')

       Import(vars...), env.Import(vars...)
           Imports variables into the current SConscript file.  vars must be
           strings representing names of variables which have been previously
           exported either by the Export function or by the exports argument
           to SConscript. Variables exported by SConscript take precedence.
           Multiple variable names can be passed to Import as separate
           arguments or as words in a space-separated string. The wildcard "*"
           can be used to import all available variables.

           Examples:

               Import("env")
               Import("env", "variable")
               Import(["env", "variable"])
               Import("*")

       Literal(string), env.Literal(string)
           The specified string will be preserved as-is and not have
           construction variables expanded.

       Local(targets), env.Local(targets)
           The specified targets will have copies made in the local tree, even
           if an already up-to-date copy exists in a repository. Returns a
           list of the target Node or Nodes.

       env.MergeFlags(arg, [unique])
           Merges values from arg into construction variables in the current
           construction environment. If arg is not a dictionary, it is
           converted to one by calling env.ParseFlags on the argument before
           the values are merged. Note that arg must be a single value, so
           multiple strings must be passed in as a list, not as separate
           arguments to env.MergeFlags.

           By default, duplicate values are eliminated; you can, however,
           specify unique=False to allow duplicate values to be added. When
           eliminating duplicate values, any construction variables that end
           with the string PATH keep the left-most unique value. All other
           construction variables keep the right-most unique value.

           Examples:

               # Add an optimization flag to $CCFLAGS.
               env.MergeFlags('-O3')

               # Combine the flags returned from running pkg-config with an optimization
               # flag and merge the result into the construction variables.
               env.MergeFlags(['!pkg-config gtk+-2.0 --cflags', '-O3'])

               # Combine an optimization flag with the flags returned from running pkg-config
               # twice and merge the result into the construction variables.
               env.MergeFlags(['-O3',
                              '!pkg-config gtk+-2.0 --cflags --libs',
                              '!pkg-config libpng12 --cflags --libs'])

       NoCache(target, ...), env.NoCache(target, ...)
           Specifies a list of files which should not be cached whenever the
           CacheDir method has been activated. The specified targets may be a
           list or an individual target.

           Multiple files should be specified either as separate arguments to
           the NoCache method, or as a list.  NoCache will also accept the
           return value of any of the construction environment Builder
           methods.

           Calling NoCache on directories and other non-File Node types has no
           effect because only File Nodes are cached.

           Examples:

               NoCache('foo.elf')
               NoCache(env.Program('hello', 'hello.c'))

       NoClean(target, ...), env.NoClean(target, ...)
           Specifies a list of files or directories which should not be
           removed whenever the targets (or their dependencies) are specified
           with the -c command line option. The specified targets may be a
           list or an individual target. Multiple calls to NoClean are legal,
           and prevent each specified target from being removed by calls to
           the -c option.

           Multiple files or directories should be specified either as
           separate arguments to the NoClean method, or as a list.  NoClean
           will also accept the return value of any of the construction
           environment Builder methods.

           Calling NoClean for a target overrides calling Clean for the same
           target, and any targets passed to both functions will not be
           removed by the -c option.

           Examples:

               NoClean('foo.elf')
               NoClean(env.Program('hello', 'hello.c'))

       env.ParseConfig(command, [function, unique])
           Updates the current construction environment with the values
           extracted from the output from running external command, by calling
           a helper function function which understands the output of command.
           command may be a string or a list of strings representing the
           command and its arguments. If function is not given, env.MergeFlags
           is used. By default, duplicate values are not added to any
           construction variables; you can specify unique=False to allow
           duplicate values to be added.

           If env.MergeFlags is used, it expects a response in the style of a
           *-config command typical of the POSIX programming environment (for
           example, gtk-config) and adds the options to the appropriate
           construction variables. Interpreted options and the construction
           variables they affect are as specified for the env.ParseFlags
           method (which env.MergeFlags calls). See that method's description
           for a table of options and corresponding construction variables.

           If env.MergeFlags cannot interpret the results of command, you can
           suppply a custom function to do so.  function must accept three
           arguments: the construction environment to modify, the string
           returned by running command, and the optional unique flag.

       ParseDepends(filename, [must_exist, only_one]),
       env.ParseDepends(filename, [must_exist, only_one])
           Parses the contents of the specified filename as a list of
           dependencies in the style of Make or mkdep, and explicitly
           establishes all of the listed dependencies.

           By default, it is not an error if the specified filename does not
           exist. The optional must_exist argument may be set to a non-zero
           value to have scons throw an exception and generate an error if the
           file does not exist, or is otherwise inaccessible.

           The optional only_one argument may be set to a non-zero value to
           have scons thrown an exception and generate an error if the file
           contains dependency information for more than one target. This can
           provide a small sanity check for files intended to be generated by,
           for example, the gcc -M flag, which should typically only write
           dependency information for one output file into a corresponding .d
           file.

           The filename and all of the files listed therein will be
           interpreted relative to the directory of the SConscript file which
           calls the ParseDepends function.

       env.ParseFlags(flags, ...)
           Parses one or more strings containing typical command-line flags
           for GCC tool chains and returns a dictionary with the flag values
           separated into the appropriate SCons construction variables. This
           is intended as a companion to the env.MergeFlags method, but allows
           for the values in the returned dictionary to be modified, if
           necessary, before merging them into the construction environment.
           (Note that env.MergeFlags will call this method if its argument is
           not a dictionary, so it is usually not necessary to call
           env.ParseFlags directly unless you want to manipulate the values.)

           If the first character in any string is an exclamation mark (!),
           the rest of the string is executed as a command, and the output
           from the command is parsed as GCC tool chain command-line flags and
           added to the resulting dictionary.

           Flag values are translated accordig to the prefix found, and added
           to the following construction variables:

               -arch                   CCFLAGS, LINKFLAGS
               -D                      CPPDEFINES
               -framework              FRAMEWORKS
               -frameworkdir=          FRAMEWORKPATH
               -fmerge-all-constants   CCFLAGS, LINKFLAGS
               -fopenmp                CCFLAGS, LINKFLAGS
               -include                CCFLAGS
               -imacros                CCFLAGS
               -isysroot               CCFLAGS, LINKFLAGS
               -isystem                CCFLAGS
               -iquote                 CCFLAGS
               -idirafter              CCFLAGS
               -I                      CPPPATH
               -l                      LIBS
               -L                      LIBPATH
               -mno-cygwin             CCFLAGS, LINKFLAGS
               -mwindows               LINKFLAGS
               -openmp                 CCFLAGS, LINKFLAGS
               -pthread                CCFLAGS, LINKFLAGS
               -std=                   CFLAGS
               -Wa,                    ASFLAGS, CCFLAGS
               -Wl,-rpath=             RPATH
               -Wl,-R,                 RPATH
               -Wl,-R                  RPATH
               -Wl,                    LINKFLAGS
               -Wp,                    CPPFLAGS
               -                       CCFLAGS
               +                       CCFLAGS, LINKFLAGS

           Any other strings not associated with options are assumed to be the
           names of libraries and added to the $LIBS construction variable.

           Examples (all of which produce the same result):

               dict = env.ParseFlags('-O2 -Dfoo -Dbar=1')
               dict = env.ParseFlags('-O2', '-Dfoo', '-Dbar=1')
               dict = env.ParseFlags(['-O2', '-Dfoo -Dbar=1'])
               dict = env.ParseFlags('-O2', '!echo -Dfoo -Dbar=1')

       Platform(string)
           The Platform form returns a callable object that can be used to
           initialize a construction environment using the platform keyword of
           the Environment function.

           Example:

               env = Environment(platform=Platform('win32'))

           The env.Platform form applies the callable object for the specified
           platform string to the environment through which the method was
           called.

               env.Platform('posix')

           Note that the win32 platform adds the SystemDrive and SystemRoot
           variables from the user's external environment to the construction
           environment's $ENV dictionary. This is so that any executed
           commands that use sockets to connect with other systems (such as
           fetching source files from external CVS repository specifications
           like :pserver:anonymous@cvs.sourceforge.net:/cvsroot/scons) will
           work on Windows systems.

       Precious(target, ...), env.Precious(target, ...)
           Marks each given target as precious so it is not deleted before it
           is rebuilt. Normally scons deletes a target before building it.
           Multiple targets can be passed in to a single call to Precious.

       env.Prepend(key=val, [...])
           Prepend values to construction variables in the current
           construction environment, Works like env.Append (see for details),
           except that values are added to the front, rather than the end, of
           any existing value of the construction variable

           Example:

               env.Prepend(CCFLAGS='-g ', FOO=['foo.yyy'])

           See also env.Append, env.AppendUnique and env.PrependUnique.

       env.PrependENVPath(name, newpath, [envname, sep, delete_existing])
           Prepend new path elements to the given path in the specified
           external environment ($ENV by default). This will only add any
           particular path once (leaving the first one it encounters and
           ignoring the rest, to preserve path order), and to help assure
           this, will normalize all paths (using os.path.normpath and
           os.path.normcase). This can also handle the case where the given
           old path variable is a list instead of a string, in which case a
           list will be returned instead of a string.

           If delete_existing is False, then adding a path that already exists
           will not move it to the beginning; it will stay where it is in the
           list.

           Example:

               print('before:', env['ENV']['INCLUDE'])
               include_path = '/foo/bar:/foo'
               env.PrependENVPath('INCLUDE', include_path)
               print('after:', env['ENV']['INCLUDE'])

           Yields:

               before: /biz:/foo
               after: /foo/bar:/foo:/biz

       env.PrependUnique(key=val, delete_existing=False, [...])
           Prepend values to construction variables in the current
           construction environment, maintaining uniqueness. Works like
           env.Append (see for details), except that values are added to the
           front, rather than the end, of any existing value of the the
           construction variable, and values already present in the
           construction variable will not be added again. If delete_existing
           is True, the existing matching value is first removed, and the
           requested value is inserted, having the effect of moving such
           values to the front.

           Example:

               env.PrependUnique(CCFLAGS='-g', FOO=['foo.yyy'])

           See also env.Append, env.AppendUnique and env.Prepend.

       Progress(callable, [interval]), Progress(string, [interval, file,
       overwrite]), Progress(list_of_strings, [interval, file, overwrite])
           Allows SCons to show progress made during the build by displaying a
           string or calling a function while evaluating Nodes (e.g. files).

           If the first specified argument is a Python callable (a function or
           an object that has a __call__ method), the function will be called
           once every interval times a Node is evaluated (default 1). The
           callable will be passed the evaluated Node as its only argument.
           (For future compatibility, it's a good idea to also add *args and
           **kwargs as arguments to your function or method signatures. This
           will prevent the code from breaking if SCons ever changes the
           interface to call the function with additional arguments in the
           future.)

           An example of a simple custom progress function that prints a
           string containing the Node name every 10 Nodes:

               def my_progress_function(node, *args, **kwargs):
                   print('Evaluating node %s!' % node)
               Progress(my_progress_function, interval=10)

           A more complicated example of a custom progress display object that
           prints a string containing a count every 100 evaluated Nodes. Note
           the use of \r (a carriage return) at the end so that the string
           will overwrite itself on a display:

               import sys
               class ProgressCounter(object):
                   count = 0
                   def __call__(self, node, *args, **kw):
                       self.count += 100
                       sys.stderr.write('Evaluated %s nodes\r' % self.count)

               Progress(ProgressCounter(), interval=100)

           If the first argument to Progress is a string or list of strings,
           it is taken as text to be displayed every interval evaluated Nodes.
           If the first argument is a list of strings, then each string in the
           list will be displayed in rotating fashion every interval evaluated
           Nodes.

           The default is to print the string on standard output. An alternate
           output stream may be specified with the file keyword argument,
           which the caller must pass already opened.

           The following will print a series of dots on the error output, one
           dot for every 100 evaluated Nodes:

               import sys
               Progress('.', interval=100, file=sys.stderr)

           If the string contains the verbatim substring $TARGET;, it will be
           replaced with the Node. Note that, for performance reasons, this is
           not a regular SCons variable substition, so you can not use other
           variables or use curly braces. The following example will print the
           name of every evaluated Node, using a carriage return) (\r) to
           cause each line to overwritten by the next line, and the overwrite
           keyword argument (default False) to make sure the
           previously-printed file name is overwritten with blank spaces:

               import sys
               Progress('$TARGET\r', overwrite=True)

           A list of strings can be used to implement a "spinner" on the
           user's screen as follows, changing every five evaluated Nodes:

               Progress(['-\r', '\\\r', '|\r', '/\r'], interval=5)

       Pseudo(target, ...), env.Pseudo(target, ...)
           This indicates that each given target should not be created by the
           build rule, and if the target is created, an error will be
           generated. This is similar to the gnu make .PHONY target. However,
           in the vast majority of cases, an Alias is more appropriate.
           Multiple targets can be passed in to a single call to Pseudo.

       PyPackageDir(modulename), env.PyPackageDir(modulename)
           This returns a Directory Node similar to Dir. The python module /
           package is looked up and if located the directory is returned for
           the location.  modulename Is a named python package / module to
           lookup the directory for it's location.

           If modulename is a list, SCons returns a list of Dir nodes.
           Construction variables are expanded in modulename.

       env.Replace(key=val, [...])
           Replaces construction variables in the Environment with the
           specified keyword arguments.

           Example:

               env.Replace(CCFLAGS='-g', FOO='foo.xxx')

       Repository(directory), env.Repository(directory)
           Specifies that directory is a repository to be searched for files.
           Multiple calls to Repository are legal, and each one adds to the
           list of repositories that will be searched.

           To scons, a repository is a copy of the source tree, from the
           top-level directory on down, which may contain both source files
           and derived files that can be used to build targets in the local
           source tree. The canonical example would be an official source tree
           maintained by an integrator. If the repository contains derived
           files, then the derived files should have been built using scons,
           so that the repository contains the necessary signature information
           to allow scons to figure out when it is appropriate to use the
           repository copy of a derived file, instead of building one locally.

           Note that if an up-to-date derived file already exists in a
           repository, scons will not make a copy in the local directory tree.
           In order to guarantee that a local copy will be made, use the Local
           method.

       Requires(target, prerequisite), env.Requires(target, prerequisite)
           Specifies an order-only relationship between the specified target
           file(s) and the specified prerequisite file(s). The prerequisite
           file(s) will be (re)built, if necessary, before the target file(s),
           but the target file(s) do not actually depend on the prerequisites
           and will not be rebuilt simply because the prerequisite file(s)
           change.

           Example:

               env.Requires('foo', 'file-that-must-be-built-before-foo')

       Return([vars..., stop=True])
           Return to the calling SConscript, optionally returning the values
           of variables named in vars. Multiple strings contaning variable
           names may be passed to Return. A string containing white space is
           split into individual variable names. Returns the value if one
           variable is specified, else returns a tuple of values. Returns an
           empty tuple if vars is omitted.

           By default Return stops processing the current SConscript and
           returns immediately. The optional stop keyword argument may be set
           to a false value to continue processing the rest of the SConscript
           file after the Return call (this was the default behavior prior to
           SCons 0.98.) However, the values returned are still the values of
           the variables in the named vars at the point Return was called.

           Examples:

               # Returns no values (evaluates False)
               Return()

               # Returns the value of the 'foo' Python variable.
               Return("foo")

               # Returns the values of the Python variables 'foo' and 'bar'.
               Return("foo", "bar")

               # Returns the values of Python variables 'val1' and 'val2'.
               Return('val1 val2')

       Scanner(function, [name, argument, skeys, path_function, node_class,
       node_factory, scan_check, recursive]), env.Scanner(function, [name,
       argument, skeys, path_function, node_class, node_factory, scan_check,
       recursive])
           Creates a Scanner object for the specified function. See manpage
           section "Scanner Objects" for a complete explanation of the
           arguments and behavior.

       SConscript(scripts, [exports, variant_dir, duplicate, must_exist]),
       env.SConscript(scripts, [exports, variant_dir, duplicate, must_exist]),
       SConscript(dirs=subdirs, [name=script, exports, variant_dir, duplicate,
       must_exist]), env.SConscript(dirs=subdirs, [name=script, exports,
       variant_dir, duplicate, must_exist])
           Execute one or more subsidiary SConscript (configuration) files.
           There are two ways to call the SConscript function.

           The first calling style is to explicitly specify one or more
           scripts as the first argument. A single script may be specified as
           a string; multiple scripts must be specified as a list (either
           explicitly or as created by a function like Split). Examples:

               SConscript('SConscript')      # run SConscript in the current directory
               SConscript('src/SConscript')  # run SConscript in the src directory
               SConscript(['src/SConscript', 'doc/SConscript'])
               config = SConscript('MyConfig.py')

           The second way to call SConscript is to specify a list of
           (sub)directory names as a dirs=subdirs keyword argument. In this
           case, scons will execute a subsidiary configuration file named
           SConscript in each of the specified directories. You may specify a
           name other than SConscript by supplying an optional name=script
           keyword argument. The first three examples below have the same
           effect as the first three examples above:

               SConscript(dirs='.')      # run SConscript in the current directory
               SConscript(dirs='src')    # run SConscript in the src directory
               SConscript(dirs=['src', 'doc'])
               SConscript(dirs=['sub1', 'sub2'], name='MySConscript')

           The optional exports argument provides a string or list of strings
           representing variable names, or a dictionary of named values, to
           export. These variables are locally exported only to the called
           SConscript file(s) and do not affect the global pool of variables
           managed by the Export function.  The subsidiary SConscript files
           must use the Import function to import the variables. Examples:

               foo = SConscript('sub/SConscript', exports='env')
               SConscript('dir/SConscript', exports=['env', 'variable'])
               SConscript(dirs='subdir', exports='env variable')
               SConscript(dirs=['one', 'two', 'three'], exports='shared_info')

           If the optional variant_dir argument is present, it causes an
           effect equivalent to the VariantDir function. The variant_dir
           argument is interpreted relative to the directory of the calling
           SConscript file. The optional duplicate argument is interpreted as
           for VariantDir. If variant_dir is omitted, the duplicate argument
           is ignored. See the description of VariantDir below for additional
           details and restrictions.

           If variant_dir is present, the source directory is the directory in
           which the SConscript file resides and the SConscript file is
           evaluated as if it were in the variant_dir directory:

               SConscript('src/SConscript', variant_dir='build')

           is equivalent to

               VariantDir('build', 'src')
               SConscript('build/SConscript')

           This later paradigm is often used when the sources are in the same
           directory as the SConstruct:

               SConscript('SConscript', variant_dir='build')

           is equivalent to

               VariantDir('build', '.')
               SConscript('build/SConscript')



           If the optional must_exist is True, causes an exception to be
           raised if a requested SConscript file is not found. The current
           default is False, causing only a warning to be emitted, but this
           default is deprecated (since 3.1). For scripts which truly intend
           to be optional, transition to explicitly supplying must_exist=False
           to the SConscript call.

           Here are some composite examples:

               # collect the configuration information and use it to build src and doc
               shared_info = SConscript('MyConfig.py')
               SConscript('src/SConscript', exports='shared_info')
               SConscript('doc/SConscript', exports='shared_info')

               # build debugging and production versions.  SConscript
               # can use Dir('.').path to determine variant.
               SConscript('SConscript', variant_dir='debug', duplicate=0)
               SConscript('SConscript', variant_dir='prod', duplicate=0)

               # build debugging and production versions.  SConscript
               # is passed flags to use.
               opts = { 'CPPDEFINES' : ['DEBUG'], 'CCFLAGS' : '-pgdb' }
               SConscript('SConscript', variant_dir='debug', duplicate=0, exports=opts)
               opts = { 'CPPDEFINES' : ['NODEBUG'], 'CCFLAGS' : '-O' }
               SConscript('SConscript', variant_dir='prod', duplicate=0, exports=opts)

               # build common documentation and compile for different architectures
               SConscript('doc/SConscript', variant_dir='build/doc', duplicate=0)
               SConscript('src/SConscript', variant_dir='build/x86', duplicate=0)
               SConscript('src/SConscript', variant_dir='build/ppc', duplicate=0)


           SConscript returns the values of any variables named by the
           executed SConscript(s) in arguments to the Return function (see
           above for details). If a single SConscript call causes multiple
           scripts to be executed, the return value is a tuple containing the
           returns of all of the scripts. If an executed script does not
           explicitly call Return, it returns None.

       SConscriptChdir(value), env.SConscriptChdir(value)
           By default, scons changes its working directory to the directory in
           which each subsidiary SConscript file lives. This behavior may be
           disabled by specifying either:

               SConscriptChdir(0)
               env.SConscriptChdir(0)

           in which case scons will stay in the top-level directory while
           reading all SConscript files. (This may be necessary when building
           from repositories, when all the directories in which SConscript
           files may be found don't necessarily exist locally.) You may enable
           and disable this ability by calling SConscriptChdir() multiple
           times.

           Example:

               env = Environment()
               SConscriptChdir(0)
               SConscript('foo/SConscript')  # will not chdir to foo
               env.SConscriptChdir(1)
               SConscript('bar/SConscript')  # will chdir to bar

       SConsignFile([name, dbm_module]), env.SConsignFile([name, dbm_module])
           Specify where to store the SCons file signature database, and which
           database format to use. This may be useful to specify alternate
           database files and/or file locations for different types of builds.

           The optional name argument is the base name of the database
           file(s). If not an absolute path name, these are placed relative to
           the directory containing the top-level SConstruct file. The default
           is .sconsign. The actual database file(s) stored on disk may have
           an appropriate suffix appended by the chosen dbm_module

           The optional dbm_module argument specifies which Python database
           module to use for reading/writing the file. The module must be
           imported first; then the imported module name is passed as the
           argument. The default is a custom SCons.dblite module that uses
           pickled Python data structures, which works on all Python versions.
           See documentation of the Python dbm module for other available
           types.

           If called with no arguments, the database will default to
           .sconsign.dblite in the top directory of the project, which is also
           the default if if SConsignFile is not called.

           The setting is global, so the only difference between the global
           function and the environment method form is variable expansion on
           name. There should only be one active call to this function/method
           in a given build setup.

           If name is set to None, scons will store file signatures in a
           separate .sconsign file in each directory, not in a single combined
           database file. This is a backwards-compatibility meaure to support
           what was the default behavior prior to SCons 0.97 (i.e. before
           2008). Use of this mode is discouraged and may be deprecated in a
           future SCons release.

           Examples:

               # Explicitly stores signatures in ".sconsign.dblite"
               # in the top-level SConstruct directory (the default behavior).
               SConsignFile()

               # Stores signatures in the file "etc/scons-signatures"
               # relative to the top-level SConstruct directory.
               # SCons will add a database suffix to this name.
               SConsignFile("etc/scons-signatures")

               # Stores signatures in the specified absolute file name.
               # SCons will add a database suffix to this name.
               SConsignFile("/home/me/SCons/signatures")

               # Stores signatures in a separate .sconsign file
               # in each directory.
               SConsignFile(None)

               # Stores signatures in a GNU dbm format .sconsign file
               import dbm.gnu
               SConsignFile(dbm_module=dbm.gnu)

       env.SetDefault(key=val, [...])
           Sets construction variables to default values specified with the
           keyword arguments if (and only if) the variables are not already
           set. The following statements are equivalent:

               env.SetDefault(FOO='foo')
               if 'FOO' not in env:
                   env['FOO'] = 'foo'

       SetOption(name, value), env.SetOption(name, value)
           Sets scons option variable name to value. These options are all
           also settable via command-line options but the variable name may
           differ from the command-line option name - see the table for
           correspondences. A value set via command-line option will take
           precedence over one set with SetOption, which allows setting a
           project default in the scripts and temporarily overriding it via
           command line.  SetOption calls can also be placed in the
           site_init.py file.

           See the documentation in the manpage for the corresponding command
           line option for information about each specific option. The value
           parameter is mandatory, for option values which are boolean in
           nature (that is, the command line option does not take an argument)
           use a value which evaluates to true (e.g.  True, 1) or false (e.g.
           False, 0).

           Options which affect the reading and processing of SConscript files
           are not settable using SetOption since those files must be read in
           order to find the SetOption call in the first place.

           The settable variables with their associated command-line options
           are:

           +------------------------+---------------------------+---------------------+
           |Settable name           | Command-line              | Notes               |
           |                        | options                   |                     |
           +------------------------+---------------------------+---------------------+
           |clean                   | -c,                       |                     |
           |                        |     --clean,              |                     |
           |                        |     --remove              |                     |
           +------------------------+---------------------------+---------------------+
           |diskcheck               | --diskcheck               |                     |
           +------------------------+---------------------------+---------------------+
           |duplicate               | --duplicate               |                     |
           +------------------------+---------------------------+---------------------+
           |experimental            | --experimental            | since 4.2           |
           +------------------------+---------------------------+---------------------+
           |hash_chunksize          | --hash-chunksize          | Actually sets       |
           |                        |                           | md5_chunksize.      |
           |                        |                           |     since 4.2       |
           +------------------------+---------------------------+---------------------+
           |hash_format             | --hash-format             | since 4.2           |
           +------------------------+---------------------------+---------------------+
           |help                    | -h, --help                |                     |
           +------------------------+---------------------------+---------------------+
           |implicit_cache          | --implicit-cache          |                     |
           +------------------------+---------------------------+---------------------+
           |implicit_deps_changed   | --implicit-deps-changed   | Also sets           |
           |                        |                           | implicit_cache.     |
           |                        |                           |     (settable since |
           |                        |                           | 4.2)                |
           +------------------------+---------------------------+---------------------+
           |implicit_deps_unchanged | --implicit-deps-unchanged | Also sets           |
           |                        |                           | implicit_cache.     |
           |                        |                           |     (settable since |
           |                        |                           | 4.2)                |
           +------------------------+---------------------------+---------------------+
           |max_drift               | --max-drift               |                     |
           +------------------------+---------------------------+---------------------+
           |md5_chunksize           | --md5-chunksize           |                     |
           +------------------------+---------------------------+---------------------+
           |no_exec                 | -n,                       |                     |
           |                        |     --no-exec,            |                     |
           |                        |     --just-print,         |                     |
           |                        |     --dry-run,            |                     |
           |                        |     --recon               |                     |
           +------------------------+---------------------------+---------------------+
           |no_progress             | -Q                        | See                 |
           |                        |                           |     [3]             |
           +------------------------+---------------------------+---------------------+
           |num_jobs                | -j, --jobs                |                     |
           +------------------------+---------------------------+---------------------+
           |random                  | --random                  |                     |
           +------------------------+---------------------------+---------------------+
           |silent                  | -s,                       |                     |
           |                        |     --silent,             |                     |
           |                        |     --quiet               |                     |
           +------------------------+---------------------------+---------------------+
           |stack_size              | --stack-size              |                     |
           +------------------------+---------------------------+---------------------+
           |warn                    | --warn                    |                     |
           +------------------------+---------------------------+---------------------+
           |----                                                                      |
           |[a] If no_progress is set via SetOption in an SConscript                  |
           |file (but not if set in a site_init.py file) there will                   |
           |still be an initial status message about reading                          |
           |SConscript files since SCons has to start reading them                    |
           |before it can see the SetOption.                                          |
           +--------------------------------------------------------------------------+
           Example:

               SetOption('max_drift', 0)

       SideEffect(side_effect, target), env.SideEffect(side_effect, target)
           Declares side_effect as a side effect of building target. Both
           side_effect and target can be a list, a file name, or a node. A
           side effect is a target file that is created or updated as a side
           effect of building other targets. For example, a Windows PDB file
           is created as a side effect of building the .obj files for a static
           library, and various log files are created updated as side effects
           of various TeX commands. If a target is a side effect of multiple
           build commands, scons will ensure that only one set of commands is
           executed at a time. Consequently, you only need to use this method
           for side-effect targets that are built as a result of multiple
           build commands.

           Because multiple build commands may update the same side effect
           file, by default the side_effect target is not automatically
           removed when the target is removed by the -c option. (Note,
           however, that the side_effect might be removed as part of cleaning
           the directory in which it lives.) If you want to make sure the
           side_effect is cleaned whenever a specific target is cleaned, you
           must specify this explicitly with the Clean or env.Clean function.

           This function returns the list of side effect Node objects that
           were successfully added. If the list of side effects contained any
           side effects that had already been added, they are not added and
           included in the returned list.

       Split(arg), env.Split(arg)
           Returns a list of file names or other objects. If arg is a string,
           it will be split on strings of white-space characters within the
           string, making it easier to write long lists of file names. If arg
           is already a list, the list will be returned untouched. If arg is
           any other type of object, it will be returned as a list containing
           just the object.

           Example:

               files = Split("f1.c f2.c f3.c")
               files = env.Split("f4.c f5.c f6.c")
               files = Split("""
                      f7.c
                      f8.c
                      f9.c
               """)

       env.subst(input, [raw, target, source, conv])
           Performs construction variable interpolation on the specified
           string or sequence argument input.

           By default, leading or trailing white space will be removed from
           the result. and all sequences of white space will be compressed to
           a single space character. Additionally, any $( and $) character
           sequences will be stripped from the returned string, The optional
           raw argument may be set to 1 if you want to preserve white space
           and $(-$) sequences. The raw argument may be set to 2 if you want
           to strip all characters between any $( and $) pairs (as is done for
           signature calculation).

           If the input is a sequence (list or tuple), the individual elements
           of the sequence will be expanded, and the results will be returned
           as a list.

           The optional target and source keyword arguments must be set to
           lists of target and source nodes, respectively, if you want the
           $TARGET, $TARGETS, $SOURCE and $SOURCES to be available for
           expansion. This is usually necessary if you are calling env.subst
           from within a Python function used as an SCons action.

           Returned string values or sequence elements are converted to their
           string representation by default. The optional conv argument may
           specify a conversion function that will be used in place of the
           default. For example, if you want Python objects (including SCons
           Nodes) to be returned as Python objects, you can use the Python
           idiom to pass in an unnamed function that simply returns its
           unconverted argument.

           Example:

               print(env.subst("The C compiler is: $CC"))

               def compile(target, source, env):
                   sourceDir = env.subst(
                       "${SOURCE.srcdir}",
                       target=target,
                       source=source
                   )

               source_nodes = env.subst('$EXPAND_TO_NODELIST', conv=lambda x: x)

       Tag(node, tags)
           Annotates file or directory Nodes with information about how the
           Package Builder should package those files or directories. All
           Node-level tags are optional.

           Examples:

               # makes sure the built library will be installed with 644 file access mode
               Tag(Library('lib.c'), UNIX_ATTR="0o644")

               # marks file2.txt to be a documentation file
               Tag('file2.txt', DOC)

       Tool(name, [toolpath, **kwargs]), env.Tool(name, [toolpath, **kwargs])
           Locates the tool specification module name and returns a callable
           tool object for that tool. The tool module is searched for in
           standard locations and in any paths specified by the optional
           toolpath parameter. The standard locations are SCons' own internal
           path for tools plus the toolpath, if any (see the Tools section in
           the manual page for more details). Any additional keyword arguments
           kwargs are passed to the tool module's generate function during
           tool object construction.

           When called, the tool object updates a construction environment
           with construction variables and arranges any other initialization
           needed to use the mechanisms that tool describes.

           When the env.Tool form is used, the tool object is automatically
           called to update env and the value of tool is appended to the
           $TOOLS construction variable in that environment.

           Examples:

               env.Tool('gcc')
               env.Tool('opengl', toolpath=['build/tools'])

           When the global function Tool form is used, the tool object is
           constructed but not called, as it lacks the context of an
           environment to update. The tool object can be passed to an
           Environment or Clone call as part of the tools keyword argument, in
           which case the tool is applied to the environment being
           constructed, or it can be called directly, in which case a
           construction environment to update must be passed as the argument.
           Either approach will also update the $TOOLS construction variable.

           Examples:

               env = Environment(tools=[Tool('msvc')])

               env = Environment()
               msvctool = Tool('msvc')
               msvctool(env)  # adds 'msvc' to the TOOLS variable
               gltool = Tool('opengl', toolpath = ['tools'])
               gltool(env)  # adds 'opengl' to the TOOLS variable


           Changed in SCons 4.2: env.Tool now returns the tool object,
           previously it did not return (i.e. returned None).

       Value(value, [built_value], [name]), env.Value(value, [built_value],
       [name])
           Returns a Node object representing the specified Python value.
           Value Nodes can be used as dependencies of targets. If the result
           of calling str(value) changes between SCons runs, any targets
           depending on Value(value) will be rebuilt. (This is true even when
           using timestamps to decide if files are up-to-date.) When using
           timestamp source signatures, Value Nodes' timestamps are equal to
           the system time when the Node is created.  name can be provided as
           an alternative name for the resulting Value node; this is advised
           if the value parameter can't be converted to a string.

           The returned Value Node object has a write() method that can be
           used to "build" a Value Node by setting a new value. The optional
           built_value argument can be specified when the Value Node is
           created to indicate the Node should already be considered "built."
           There is a corresponding read() method that will return the built
           value of the Node.

           Examples:

               env = Environment()

               def create(target, source, env):
                   # A function that will write a 'prefix=$SOURCE'
                   # string into the file name specified as the
                   # $TARGET.
                   with open(str(target[0]), 'wb') as f:
                       f.write('prefix=' + source[0].get_contents())

               # Fetch the prefix= argument, if any, from the command
               # line, and use /usr/local as the default.
               prefix = ARGUMENTS.get('prefix', '/usr/local')

               # Attach a .Config() builder for the above function action
               # to the construction environment.
               env['BUILDERS']['Config'] = Builder(action = create)
               env.Config(target = 'package-config', source = Value(prefix))

               def build_value(target, source, env):
                   # A function that "builds" a Python Value by updating
                   # the the Python value with the contents of the file
                   # specified as the source of the Builder call ($SOURCE).
                   target[0].write(source[0].get_contents())

               output = env.Value('before')
               input = env.Value('after')

               # Attach a .UpdateValue() builder for the above function
               # action to the construction environment.
               env['BUILDERS']['UpdateValue'] = Builder(action = build_value)
               env.UpdateValue(target = Value(output), source = Value(input))

       VariantDir(variant_dir, src_dir, [duplicate]),
       env.VariantDir(variant_dir, src_dir, [duplicate])
           Sets up an alternate build location. When building in the
           variant_dir, SCons backfills as needed with files from src_dir to
           create a complete build directory.  VariantDir can be called
           multiple times with the same src_dir to set up multiple builds with
           different options (variants).

           The variant location must be in or underneath the project top
           directory, and src_dir may not be underneath variant_dir.

           By default, SCons physically duplicates the source files and
           SConscript files as needed into the variant tree. Thus, a build
           performed in the variant tree is guaranteed to be identical to a
           build performed in the source tree even if intermediate source
           files are generated during the build, or if preprocessors or other
           scanners search for included files relative to the source file, or
           if individual compilers or other invoked tools are hard-coded to
           put derived files in the same directory as source files. Only the
           files SCons calculates are needed for the build are duplicated into
           variant_dir.

           If possible on the platform, the duplication is performed by
           linking rather than copying. This behavior is affected by the
           --duplicate command-line option.

           Duplicating the source files may be disabled by setting the
           duplicate argument to False. This will cause SCons to invoke
           Builders using the path names of source files in src_dir and the
           path names of derived files within variant_dir. This is more
           efficient than duplicate=True, and is safe for most builds; revert
           to True if it causes problems.


           VariantDir works most naturally with used with a subsidiary
           SConscript file. The subsidiary SConscript file is called as if it
           were in variant_dir, regardless of the value of duplicate. This is
           how you tell scons which variant of a source tree to build:

               # run src/SConscript in two variant directories
               VariantDir('build/variant1', 'src')
               SConscript('build/variant1/SConscript')
               VariantDir('build/variant2', 'src')
               SConscript('build/variant2/SConscript')

           See also the SConscript function, described above, for another way
           to specify a variant directory in conjunction with calling a
           subsidiary SConscript file.

           Examples:

               # use names in the build directory, not the source directory
               VariantDir('build', 'src', duplicate=0)
               Program('build/prog', 'build/source.c')

               # this builds both the source and docs in a separate subtree
               VariantDir('build', '.', duplicate=0)
               SConscript(dirs=['build/src','build/doc'])

               # same as previous example, but only uses SConscript
               SConscript(dirs='src', variant_dir='build/src', duplicate=0)
               SConscript(dirs='doc', variant_dir='build/doc', duplicate=0)

       WhereIs(program, [path, pathext, reject]), env.WhereIs(program, [path,
       pathext, reject])
           Searches for the specified executable program, returning the full
           path to the program or None.

           When called as a construction environment method, searches the
           paths in the path keyword argument, or if None (the default) the
           paths listed in the construction environment (env['ENV']['PATH']).
           The external environment's path list (os.environ['PATH']) is used
           as a fallback if the key env['ENV']['PATH'] does not exist.

           On Windows systems, searches for executable programs with any of
           the file extensions listed in the pathext keyword argument, or if
           None (the default) the pathname extensions listed in the
           construction environment (env['ENV']['PATHEXT']). The external
           environment's pathname extensions list (os.environ['PATHEXT']) is
           used as a fallback if the key env['ENV']['PATHEXT'] does not exist.

           When called as a global function, uses the external environment's
           path os.environ['PATH'] and path extensions os.environ['PATHEXT'],
           respectively, if path and pathext are None.

           Will not select any path name or names in the optional reject list.

   SConscript Variables
       In addition to the global functions and methods, scons supports a
       number of variables that can be used in SConscript files to affect how
       you want the build to be performed.

       ARGLIST
           A list of the keyword=value arguments specified on the command
           line. Each element in the list is a tuple containing the argument.
           The separate keyword and value elements of the tuple can be
           accessed by subscripting for elements [0] and [1] of the tuple, or,
           more readably, by using tuple unpacking. Example:

               print("first keyword, value =", ARGLIST[0][0], ARGLIST[0][1])
               print("second keyword, value =", ARGLIST[1][0], ARGLIST[1][1])
               key, value = ARGLIST[2]
               print("third keyword, value =", key, value)
               for key, value in ARGLIST:
                   # process key and value

       ARGUMENTS
           A dictionary of all the keyword=value arguments specified on the
           command line. The dictionary is not in order, and if a given
           keyword has more than one value assigned to it on the command line,
           the last (right-most) value is the one in the ARGUMENTS dictionary.

           Example:

               if ARGUMENTS.get('debug', 0):
                   env = Environment(CCFLAGS='-g')
               else:
                   env = Environment()

       BUILD_TARGETS
           A list of the targets which scons has been asked to build. The
           contents will be either those targets listed on the command line,
           or, if none, those targets set via calls to the Default function.
           It does not contain any dependent targets that scons selects for
           building as a result of making the sure the specified targets are
           up to date, if those targets did not appear on the command line.
           The list is empty if neither command line targets or Default calls
           are present.

           The elements of this list may be strings or nodes, so you should
           run the list through the Python str function to make sure any Node
           path names are converted to strings.

           Because this list may be taken from the list of targets specified
           using the Default function, the contents of the list may change on
           each successive call to Default. See the DEFAULT_TARGETS list,
           below, for additional information.

           Example:

               if 'foo' in BUILD_TARGETS:
                   print("Don't forget to test the `foo' program!")
               if 'special/program' in BUILD_TARGETS:
                   SConscript('special')

       COMMAND_LINE_TARGETS
           A list of the targets explicitly specified on the command line. If
           there are command line targets, this list will have the same
           contents as BUILD_TARGETS. If there are no targets specified on the
           command line, the list is empty. The elements of this list are
           strings. This can be used, for example, to take specific actions
           only when certain targets are explicitly being built.

           Example:

               if 'foo' in COMMAND_LINE_TARGETS:
                   print("Don't forget to test the `foo' program!")
               if 'special/program' in COMMAND_LINE_TARGETS:
                   SConscript('special')

       DEFAULT_TARGETS
           A list of the target nodes that have been specified using the
           Default function. If there are no command line targets, this list
           will have the same contents as BUILD_TARGETS. Since the elements of
           the list are nodes, you need to call the Python str function on
           them to get the path name for each Node.

           Example:

               print(str(DEFAULT_TARGETS[0]))
               if 'foo' in [str(t) for t in DEFAULT_TARGETS]:
                   print("Don't forget to test the `foo' program!")

           The contents of the DEFAULT_TARGETS list change on on each
           successive call to the Default function:

               print([str(t) for t in DEFAULT_TARGETS])   # originally []
               Default('foo')
               print([str(t) for t in DEFAULT_TARGETS])   # now a node ['foo']
               Default('bar')
               print([str(t) for t in DEFAULT_TARGETS])   # now a node ['foo', 'bar']
               Default(None)
               print([str(t) for t in DEFAULT_TARGETS])   # back to []

           Consequently, be sure to use DEFAULT_TARGETS only after you've made
           all of your Default() calls, or else simply be careful of the order
           of these statements in your SConscript files so that you don't look
           for a specific default target before it's actually been added to
           the list.

       These variables may be accessed from custom Python modules that you
       import into an SConscript file by adding the following to the Python
       module:

           from SCons.Script import *

   Construction Variables
       A construction environment has an associated dictionary of construction
       variables that are used by built-in or user-supplied build rules.
       Construction variable naming must follow the same rules as Python
       identifier naming: the initial character must be an underscore or
       letter, followed by any number of underscores, letters, or digits. A
       construction environment is not a Python dictionary itself, but it can
       be indexed like one to access a construction variable:

           env["CC"] = "cc"
           flags = env.get("CPPDEFINES", [])

       Construction variables can also be retrieved and set by using the
       Dictionary method of the construction environment to create an actual
       dictionary:

           cvars = env.Dictionary()
           cvars["CC"] = "cc"

       Construction variables can also be passed to the construction
       environment constructor:

           env = Environment(CC="cc")

       or when copying a construction environment using the Clone method:

           env2 = env.Clone(CC="cl.exe")

       Construction variables can also be supplied as keyword arguments to a
       builder, in which case those settings affect only the work done by that
       builder call, and not the construction environment as a whole. This
       concept is called an override:

           env.Program('hello', 'hello.c', LIBS=['gl', 'glut'])

       A number of useful construction variables are automatically defined by
       scons for each supported platform, and you can modify these or define
       any additional construction variables for your own use, taking care not
       to overwrite ones which SCons is using. The following is a list of the
       possible automatically defined construction variables.

       Note the actual list available at execution time will never include all
       of these, as the ones detected as not being useful (wrong platform,
       necessary external command or files not installed, etc.) will not be
       set up. Correct build setups should be resilient to the possible
       absence of certain construction variables before using them, for
       example by using a Python dictionary get method to retrieve the value
       and taking alternative action if the return indicates the variable is
       unset. The env.Dump method can be called to examine the construction
       variables set in a particular environment.

       __LDMODULEVERSIONFLAGS
           This construction variable automatically introduces
           $_LDMODULEVERSIONFLAGS if $LDMODULEVERSION is set. Othervise it
           evaluates to an empty string.

       __NINJA_NO
           Internal flag. Used to tell SCons whether or not to try to import
           pypi's ninja python package. This is set to True when being called
           by Ninja?

       __SHLIBVERSIONFLAGS
           This construction variable automatically introduces
           $_SHLIBVERSIONFLAGS if $SHLIBVERSION is set. Othervise it evaluates
           to an empty string.

       APPLELINK_COMPATIBILITY_VERSION
           On Mac OS X this is used to set the linker flag:
           -compatibility_version

           The value is specified as X[.Y[.Z]] where X is between 1 and 65535,
           Y can be omitted or between 1 and 255, Z can be omitted or between
           1 and 255. This value will be derived from $SHLIBVERSION if not
           specified. The lowest digit will be dropped and replaced by a 0.

           If the $APPLELINK_NO_COMPATIBILITY_VERSION is set then no
           -compatibility_version will be output.

           See MacOS's ld manpage for more details

       _APPLELINK_COMPATIBILITY_VERSION
           A macro (by default a generator function) used to create the linker
           flags to specify apple's linker's -compatibility_version flag. The
           default generator uses $APPLELINK_COMPATIBILITY_VERSION and
           $APPLELINK_NO_COMPATIBILITY_VERSION and $SHLIBVERSION to determine
           the correct flag.

       APPLELINK_CURRENT_VERSION
           On Mac OS X this is used to set the linker flag: -current_version

           The value is specified as X[.Y[.Z]] where X is between 1 and 65535,
           Y can be omitted or between 1 and 255, Z can be omitted or between
           1 and 255. This value will be set to $SHLIBVERSION if not
           specified.

           If the $APPLELINK_NO_CURRENT_VERSION is set then no
           -current_version will be output.

           See MacOS's ld manpage for more details

       _APPLELINK_CURRENT_VERSION
           A macro (by default a generator function) used to create the linker
           flags to specify apple's linker's -current_version flag. The
           default generator uses $APPLELINK_CURRENT_VERSION and
           $APPLELINK_NO_CURRENT_VERSION and $SHLIBVERSION to determine the
           correct flag.

       APPLELINK_NO_COMPATIBILITY_VERSION
           Set this to any True (1|True|non-empty string) value to disable
           adding -compatibility_version flag when generating versioned shared
           libraries.

           This overrides $APPLELINK_COMPATIBILITY_VERSION.

       APPLELINK_NO_CURRENT_VERSION
           Set this to any True (1|True|non-empty string) value to disable
           adding -current_version flag when generating versioned shared
           libraries.

           This overrides $APPLELINK_CURRENT_VERSION.

       AR
           The static library archiver.

       ARCHITECTURE
           Specifies the system architecture for which the package is being
           built. The default is the system architecture of the machine on
           which SCons is running. This is used to fill in the Architecture:
           field in an Ipkg control file, and the BuildArch: field in the RPM
           .spec file, as well as forming part of the name of a generated RPM
           package file.

           See the Package builder.

       ARCOM
           The command line used to generate a static library from object
           files.

       ARCOMSTR
           The string displayed when a static library is generated from object
           files. If this is not set, then $ARCOM (the command line) is
           displayed.

               env = Environment(ARCOMSTR = "Archiving $TARGET")

       ARFLAGS
           General options passed to the static library archiver.

       AS
           The assembler.

       ASCOM
           The command line used to generate an object file from an
           assembly-language source file.

       ASCOMSTR
           The string displayed when an object file is generated from an
           assembly-language source file. If this is not set, then $ASCOM (the
           command line) is displayed.

               env = Environment(ASCOMSTR = "Assembling $TARGET")

       ASFLAGS
           General options passed to the assembler.

       ASPPCOM
           The command line used to assemble an assembly-language source file
           into an object file after first running the file through the C
           preprocessor. Any options specified in the $ASFLAGS and $CPPFLAGS
           construction variables are included on this command line.

       ASPPCOMSTR
           The string displayed when an object file is generated from an
           assembly-language source file after first running the file through
           the C preprocessor. If this is not set, then $ASPPCOM (the command
           line) is displayed.

               env = Environment(ASPPCOMSTR = "Assembling $TARGET")

       ASPPFLAGS
           General options when an assembling an assembly-language source file
           into an object file after first running the file through the C
           preprocessor. The default is to use the value of $ASFLAGS.

       BIBTEX
           The bibliography generator for the TeX formatter and typesetter and
           the LaTeX structured formatter and typesetter.

       BIBTEXCOM
           The command line used to call the bibliography generator for the
           TeX formatter and typesetter and the LaTeX structured formatter and
           typesetter.

       BIBTEXCOMSTR
           The string displayed when generating a bibliography for TeX or
           LaTeX. If this is not set, then $BIBTEXCOM (the command line) is
           displayed.

               env = Environment(BIBTEXCOMSTR = "Generating bibliography $TARGET")

       BIBTEXFLAGS
           General options passed to the bibliography generator for the TeX
           formatter and typesetter and the LaTeX structured formatter and
           typesetter.

       BUILDERS
           A dictionary mapping the names of the builders available through
           the construction environment to underlying Builder objects. Custom
           builders need to be added to this to make them available.

           A platform-dependent default list of builders such as Program,
           Library etc. is used to populate this construction variable when
           the construction environment is initialized via the
           presence/absence of the tools those builders depend on.  $BUILDERS
           can be examined to learn which builders will actually be available
           at run-time.

           Note that if you initialize this construction variable through
           assignment when the construction environment is created, that value
           for $BUILDERS will override any defaults:

               bld = Builder(action='foobuild < $SOURCE > $TARGET')
               env = Environment(BUILDERS={'NewBuilder': bld})

           To instead use a new Builder object in addition to the default
           Builders, add your new Builder object like this:

               env = Environment()
               env.Append(BUILDERS={'NewBuilder': bld})

           or this:

               env = Environment()
               env['BUILDERS']['NewBuilder'] = bld

       CACHEDIR_CLASS
           The class type that SCons should use when instantiating a new
           CacheDir for the given environment. It must be a subclass of the
           SCons.CacheDir.CacheDir class.

       CC
           The C compiler.

       CCCOM
           The command line used to compile a C source file to a (static)
           object file. Any options specified in the $CFLAGS, $CCFLAGS and
           $CPPFLAGS construction variables are included on this command line.
           See also $SHCCCOM for compiling to shared objects.

       CCCOMSTR
           If set, the string displayed when a C source file is compiled to a
           (static) object file. If not set, then $CCCOM (the command line) is
           displayed. See also $SHCCCOMSTR for compiling to shared objects.

               env = Environment(CCCOMSTR = "Compiling static object $TARGET")

       CCFLAGS
           General options that are passed to the C and C++ compilers. See
           also $SHCCFLAGS for compiling to shared objects.

       CCPCHFLAGS
           Options added to the compiler command line to support building with
           precompiled headers. The default value expands expands to the
           appropriate Microsoft Visual C++ command-line options when the $PCH
           construction variable is set.

       CCPDBFLAGS
           Options added to the compiler command line to support storing
           debugging information in a Microsoft Visual C++ PDB file. The
           default value expands expands to appropriate Microsoft Visual C++
           command-line options when the $PDB construction variable is set.

           The Visual C++ compiler option that SCons uses by default to
           generate PDB information is /Z7. This works correctly with parallel
           (-j) builds because it embeds the debug information in the
           intermediate object files, as opposed to sharing a single PDB file
           between multiple object files. This is also the only way to get
           debug information embedded into a static library. Using the /Zi
           instead may yield improved link-time performance, although parallel
           builds will no longer work.

           You can generate PDB files with the /Zi switch by overriding the
           default $CCPDBFLAGS variable as follows:

               env['CCPDBFLAGS'] = ['${(PDB and "/Zi /Fd%s" % File(PDB)) or ""}']

           An alternative would be to use the /Zi to put the debugging
           information in a separate .pdb file for each object file by
           overriding the $CCPDBFLAGS variable as follows:

               env['CCPDBFLAGS'] = '/Zi /Fd${TARGET}.pdb'

       CCVERSION
           The version number of the C compiler. This may or may not be set,
           depending on the specific C compiler being used.

       CFILESUFFIX
           The suffix for C source files. This is used by the internal CFile
           builder when generating C files from Lex (.l) or YACC (.y) input
           files. The default suffix, of course, is .c (lower case). On
           case-insensitive systems (like Windows), SCons also treats .C
           (upper case) files as C files.

       CFLAGS
           General options that are passed to the C compiler (C only; not
           C++). See also $SHCFLAGS for compiling to shared objects.

       CHANGE_SPECFILE
           A hook for modifying the file that controls the packaging build
           (the .spec for RPM, the control for Ipkg, the .wxs for MSI). If
           set, the function will be called after the SCons template for the
           file has been written.

           See the Package builder.

       CHANGED_SOURCES
           A reserved variable name that may not be set or used in a
           construction environment. (See the manpage section "Variable
           Substitution" for more information).

       CHANGED_TARGETS
           A reserved variable name that may not be set or used in a
           construction environment. (See the manpage section "Variable
           Substitution" for more information).

       CHANGELOG
           The name of a file containing the change log text to be included in
           the package. This is included as the %changelog section of the RPM
           .spec file.

           See the Package builder.

       COMPILATIONDB_COMSTR
           The string displayed when the CompilationDatabase builder's action
           is run.

       COMPILATIONDB_PATH_FILTER
           A string which instructs CompilationDatabase to only include
           entries where the output member matches the pattern in the filter
           string using fnmatch, which uses glob style wildcards.

           The default value is an empty string '', which disables filtering.

       COMPILATIONDB_USE_ABSPATH
           A boolean flag to instruct CompilationDatabase whether to write the
           file and output members in the compilation database using absolute
           or relative paths.

           The default value is False (use relative paths)

       _concat
           A function used to produce variables like $_CPPINCFLAGS. It takes
           four mandatory arguments, and up to 4 additional optional
           arguments: 1) a prefix to concatenate onto each element, 2) a list
           of elements, 3) a suffix to concatenate onto each element, 4) an
           environment for variable interpolation, 5) an optional function
           that will be called to transform the list before concatenation, 6)
           an optionally specified target (Can use TARGET), 7) an optionally
           specified source (Can use SOURCE), 8) optional affect_signature
           flag which will wrap non-empty returned value with $( and $) to
           indicate the contents should not affect the signature of the
           generated command line.

                       env['_CPPINCFLAGS'] = '${_concat(INCPREFIX, CPPPATH, INCSUFFIX, __env__, RDirs, TARGET, SOURCE, affect_signature=False)}'


       CONFIGUREDIR
           The name of the directory in which Configure context test files are
           written. The default is .sconf_temp in the top-level directory
           containing the SConstruct file.

       CONFIGURELOG
           The name of the Configure context log file. The default is
           config.log in the top-level directory containing the SConstruct
           file.

       _CPPDEFFLAGS
           An automatically-generated construction variable containing the C
           preprocessor command-line options to define values. The value of
           $_CPPDEFFLAGS is created by respectively prepending and appending
           $CPPDEFPREFIX and $CPPDEFSUFFIX to each definition in $CPPDEFINES.

       CPPDEFINES
           A platform independent specification of C preprocessor macro
           definitions. The definitions will be added to command lines through
           the automatically-generated $_CPPDEFFLAGS construction variable
           (see above), which is constructed according to the type of value of
           $CPPDEFINES:

           If $CPPDEFINES is a string, the values of the $CPPDEFPREFIX and
           $CPPDEFSUFFIX construction variables will be respectively prepended
           and appended to each definition in $CPPDEFINES.

               # Will add -Dxyz to POSIX compiler command lines,
               # and /Dxyz to Microsoft Visual C++ command lines.
               env = Environment(CPPDEFINES='xyz')

           If $CPPDEFINES is a list, the values of the $CPPDEFPREFIX and
           $CPPDEFSUFFIX construction variables will be respectively prepended
           and appended to each element in the list. If any element is a list
           or tuple, then the first item is the name being defined and the
           second item is its value:

               # Will add -DB=2 -DA to POSIX compiler command lines,
               # and /DB=2 /DA to Microsoft Visual C++ command lines.
               env = Environment(CPPDEFINES=[('B', 2), 'A'])

           If $CPPDEFINES is a dictionary, the values of the $CPPDEFPREFIX and
           $CPPDEFSUFFIX construction variables will be respectively prepended
           and appended to each item from the dictionary. The key of each
           dictionary item is a name being defined to the dictionary item's
           corresponding value; if the value is None, then the name is defined
           without an explicit value. Note that the resulting flags are sorted
           by keyword to ensure that the order of the options on the command
           line is consistent each time scons is run.

               # Will add -DA -DB=2 to POSIX compiler command lines,
               # and /DA /DB=2 to Microsoft Visual C++ command lines.
               env = Environment(CPPDEFINES={'B':2, 'A':None})

       CPPDEFPREFIX
           The prefix used to specify preprocessor macro definitions on the C
           compiler command line. This will be prepended to each definition in
           the $CPPDEFINES construction variable when the $_CPPDEFFLAGS
           variable is automatically generated.

       CPPDEFSUFFIX
           The suffix used to specify preprocessor macro definitions on the C
           compiler command line. This will be appended to each definition in
           the $CPPDEFINES construction variable when the $_CPPDEFFLAGS
           variable is automatically generated.

       CPPFLAGS
           User-specified C preprocessor options. These will be included in
           any command that uses the C preprocessor, including not just
           compilation of C and C++ source files via the $CCCOM, $SHCCCOM,
           $CXXCOM and $SHCXXCOM command lines, but also the $FORTRANPPCOM,
           $SHFORTRANPPCOM, $F77PPCOM and $SHF77PPCOM command lines used to
           compile a Fortran source file, and the $ASPPCOM command line used
           to assemble an assembly language source file, after first running
           each file through the C preprocessor. Note that this variable does
           not contain -I (or similar) include search path options that scons
           generates automatically from $CPPPATH. See $_CPPINCFLAGS, below,
           for the variable that expands to those options.

       _CPPINCFLAGS
           An automatically-generated construction variable containing the C
           preprocessor command-line options for specifying directories to be
           searched for include files. The value of $_CPPINCFLAGS is created
           by respectively prepending and appending $INCPREFIX and $INCSUFFIX
           to each directory in $CPPPATH.

       CPPPATH
           The list of directories that the C preprocessor will search for
           include directories. The C/C++ implicit dependency scanner will
           search these directories for include files. In general it's not
           advised to put include directory directives directly into $CCFLAGS
           or $CXXFLAGS as the result will be non-portable and the directories
           will not be searched by the dependency scanner.  $CPPPATH should be
           a list of path strings, or a single string, not a pathname list
           joined by Python's os.sep.

           Note: directory names in $CPPPATH will be looked-up relative to the
           directory of the SConscript file when they are used in a command.
           To force scons to look-up a directory relative to the root of the
           source tree use the # prefix:

               env = Environment(CPPPATH='#/include')

           The directory look-up can also be forced using the Dir function:

               include = Dir('include')
               env = Environment(CPPPATH=include)

           The directory list will be added to command lines through the
           automatically-generated $_CPPINCFLAGS construction variable, which
           is constructed by respectively prepending and appending the values
           of the $INCPREFIX and $INCSUFFIX construction variables to each
           directory in $CPPPATH. Any command lines you define that need the
           $CPPPATH directory list should include $_CPPINCFLAGS:

               env = Environment(CCCOM="my_compiler $_CPPINCFLAGS -c -o $TARGET $SOURCE")

       CPPSUFFIXES
           The list of suffixes of files that will be scanned for C
           preprocessor implicit dependencies (#include lines). The default
           list is:

               [".c", ".C", ".cxx", ".cpp", ".c++", ".cc",
                ".h", ".H", ".hxx", ".hpp", ".hh",
                ".F", ".fpp", ".FPP",
                ".m", ".mm",
                ".S", ".spp", ".SPP"]

       CXX
           The C++ compiler. See also $SHCXX for compiling to shared objects..

       CXXCOM
           The command line used to compile a C++ source file to an object
           file. Any options specified in the $CXXFLAGS and $CPPFLAGS
           construction variables are included on this command line. See also
           $SHCXXCOM for compiling to shared objects..

       CXXCOMSTR
           If set, the string displayed when a C++ source file is compiled to
           a (static) object file. If not set, then $CXXCOM (the command line)
           is displayed. See also $SHCXXCOMSTR for compiling to shared
           objects..

               env = Environment(CXXCOMSTR = "Compiling static object $TARGET")

       CXXFILESUFFIX
           The suffix for C++ source files. This is used by the internal
           CXXFile builder when generating C++ files from Lex (.ll) or YACC
           (.yy) input files. The default suffix is .cc. SCons also treats
           files with the suffixes .cpp, .cxx, .c++, and .C++ as C++ files,
           and files with .mm suffixes as Objective C++ files. On
           case-sensitive systems (Linux, UNIX, and other POSIX-alikes), SCons
           also treats .C (upper case) files as C++ files.

       CXXFLAGS
           General options that are passed to the C++ compiler. By default,
           this includes the value of $CCFLAGS, so that setting $CCFLAGS
           affects both C and C++ compilation. If you want to add C++-specific
           flags, you must set or override the value of $CXXFLAGS. See also
           $SHCXXFLAGS for compiling to shared objects..

       CXXVERSION
           The version number of the C++ compiler. This may or may not be set,
           depending on the specific C++ compiler being used.

       DC
           The D compiler to use. See also $SHDC for compiling to shared
           objects.

       DCOM
           The command line used to compile a D file to an object file. Any
           options specified in the $DFLAGS construction variable is included
           on this command line. See also $SHDCOM for compiling to shared
           objects.

       DCOMSTR
           If set, the string displayed when a D source file is compiled to a
           (static) object file. If not set, then $DCOM (the command line) is
           displayed. See also $SHDCOMSTR for compiling to shared objects.

       DDEBUG
           List of debug tags to enable when compiling.

       DDEBUGPREFIX
           DDEBUGPREFIX.

       DDEBUGSUFFIX
           DDEBUGSUFFIX.

       DESCRIPTION
           A long description of the project being packaged. This is included
           in the relevant section of the file that controls the packaging
           build.

           See the Package builder.

       DESCRIPTION_lang
           A language-specific long description for the specified lang. This
           is used to populate a %description -l section of an RPM .spec file.

           See the Package builder.

       DFILESUFFIX
           DFILESUFFIX.

       DFLAGPREFIX
           DFLAGPREFIX.

       DFLAGS
           General options that are passed to the D compiler.

       DFLAGSUFFIX
           DFLAGSUFFIX.

       DINCPREFIX
           DINCPREFIX.

       DINCSUFFIX
           DLIBFLAGSUFFIX.

       Dir
           A function that converts a string into a Dir instance relative to
           the target being built.

       Dirs
           A function that converts a list of strings into a list of Dir
           instances relative to the target being built.

       DLIB
           Name of the lib tool to use for D codes.

       DLIBCOM
           The command line to use when creating libraries.

       DLIBDIRPREFIX
           DLIBLINKPREFIX.

       DLIBDIRSUFFIX
           DLIBLINKSUFFIX.

       DLIBFLAGPREFIX
           DLIBFLAGPREFIX.

       DLIBFLAGSUFFIX
           DLIBFLAGSUFFIX.

       DLIBLINKPREFIX
           DLIBLINKPREFIX.

       DLIBLINKSUFFIX
           DLIBLINKSUFFIX.

       DLINK
           Name of the linker to use for linking systems including D sources.
           See also $SHDLINK for linking shared objects.

       DLINKCOM
           The command line to use when linking systems including D sources.
           See also $SHDLINKCOM for linking shared objects.

       DLINKFLAGPREFIX
           DLINKFLAGPREFIX.

       DLINKFLAGS
           List of linker flags. See also $SHDLINKFLAGS for linking shared
           objects.

       DLINKFLAGSUFFIX
           DLINKFLAGSUFFIX.

       DOCBOOK_DEFAULT_XSL_EPUB
           The default XSLT file for the DocbookEpub builder within the
           current environment, if no other XSLT gets specified via keyword.

       DOCBOOK_DEFAULT_XSL_HTML
           The default XSLT file for the DocbookHtml builder within the
           current environment, if no other XSLT gets specified via keyword.

       DOCBOOK_DEFAULT_XSL_HTMLCHUNKED
           The default XSLT file for the DocbookHtmlChunked builder within the
           current environment, if no other XSLT gets specified via keyword.

       DOCBOOK_DEFAULT_XSL_HTMLHELP
           The default XSLT file for the DocbookHtmlhelp builder within the
           current environment, if no other XSLT gets specified via keyword.

       DOCBOOK_DEFAULT_XSL_MAN
           The default XSLT file for the DocbookMan builder within the current
           environment, if no other XSLT gets specified via keyword.

       DOCBOOK_DEFAULT_XSL_PDF
           The default XSLT file for the DocbookPdf builder within the current
           environment, if no other XSLT gets specified via keyword.

       DOCBOOK_DEFAULT_XSL_SLIDESHTML
           The default XSLT file for the DocbookSlidesHtml builder within the
           current environment, if no other XSLT gets specified via keyword.

       DOCBOOK_DEFAULT_XSL_SLIDESPDF
           The default XSLT file for the DocbookSlidesPdf builder within the
           current environment, if no other XSLT gets specified via keyword.

       DOCBOOK_FOP
           The path to the PDF renderer fop or xep, if one of them is
           installed (fop gets checked first).

       DOCBOOK_FOPCOM
           The full command-line for the PDF renderer fop or xep.

       DOCBOOK_FOPCOMSTR
           The string displayed when a renderer like fop or xep is used to
           create PDF output from an XML file.

       DOCBOOK_FOPFLAGS
           Additonal command-line flags for the PDF renderer fop or xep.

       DOCBOOK_XMLLINT
           The path to the external executable xmllint, if it's installed.
           Note, that this is only used as last fallback for resolving
           XIncludes, if no lxml Python binding can be imported in the current
           system.

       DOCBOOK_XMLLINTCOM
           The full command-line for the external executable xmllint.

       DOCBOOK_XMLLINTCOMSTR
           The string displayed when xmllint is used to resolve XIncludes for
           a given XML file.

       DOCBOOK_XMLLINTFLAGS
           Additonal command-line flags for the external executable xmllint.

       DOCBOOK_XSLTPROC
           The path to the external executable xsltproc (or saxon, xalan), if
           one of them is installed. Note, that this is only used as last
           fallback for XSL transformations, if no lxml Python binding can be
           imported in the current system.

       DOCBOOK_XSLTPROCCOM
           The full command-line for the external executable xsltproc (or
           saxon, xalan).

       DOCBOOK_XSLTPROCCOMSTR
           The string displayed when xsltproc is used to transform an XML file
           via a given XSLT stylesheet.

       DOCBOOK_XSLTPROCFLAGS
           Additonal command-line flags for the external executable xsltproc
           (or saxon, xalan).

       DOCBOOK_XSLTPROCPARAMS
           Additonal parameters that are not intended for the XSLT processor
           executable, but the XSL processing itself. By default, they get
           appended at the end of the command line for saxon and saxon-xslt,
           respectively.

       DPATH
           List of paths to search for import modules.

       DRPATHPREFIX
           DRPATHPREFIX.

       DRPATHSUFFIX
           DRPATHSUFFIX.

       DSUFFIXES
           The list of suffixes of files that will be scanned for imported D
           package files. The default list is ['.d'].

       DVERPREFIX
           DVERPREFIX.

       DVERSIONS
           List of version tags to enable when compiling.

       DVERSUFFIX
           DVERSUFFIX.

       DVIPDF
           The TeX DVI file to PDF file converter.

       DVIPDFCOM
           The command line used to convert TeX DVI files into a PDF file.

       DVIPDFCOMSTR
           The string displayed when a TeX DVI file is converted into a PDF
           file. If this is not set, then $DVIPDFCOM (the command line) is
           displayed.

       DVIPDFFLAGS
           General options passed to the TeX DVI file to PDF file converter.

       DVIPS
           The TeX DVI file to PostScript converter.

       DVIPSFLAGS
           General options passed to the TeX DVI file to PostScript converter.

       ENV
           A dictionary of environment variables to use when invoking
           commands. When $ENV is used in a command all list values will be
           joined using the path separator and any other non-string values
           will simply be coerced to a string. Note that, by default, scons
           does not propagate the environment in effect when you execute scons
           to the commands used to build target files. This is so that builds
           will be guaranteed repeatable regardless of the environment
           variables set at the time scons is invoked.

           If you want to propagate your environment variables to the commands
           executed to build target files, you must do so explicitly:

               import os
               env = Environment(ENV=os.environ.copy())

           Note that you can choose only to propagate certain environment
           variables. A common example is the system PATH environment
           variable, so that scons uses the same utilities as the invoking
           shell (or other process):

               import os
               env = Environment(ENV={'PATH': os.environ['PATH']})

       ESCAPE
           A function that will be called to escape shell special characters
           in command lines. The function should take one argument: the
           command line string to escape; and should return the escaped
           command line.

       F03
           The Fortran 03 compiler. You should normally set the $FORTRAN
           variable, which specifies the default Fortran compiler for all
           Fortran versions. You only need to set $F03 if you need to use a
           specific compiler or compiler version for Fortran 03 files.

       F03COM
           The command line used to compile a Fortran 03 source file to an
           object file. You only need to set $F03COM if you need to use a
           specific command line for Fortran 03 files. You should normally set
           the $FORTRANCOM variable, which specifies the default command line
           for all Fortran versions.

       F03COMSTR
           If set, the string displayed when a Fortran 03 source file is
           compiled to an object file. If not set, then $F03COM or $FORTRANCOM
           (the command line) is displayed.

       F03FILESUFFIXES
           The list of file extensions for which the F03 dialect will be used.
           By default, this is ['.f03']

       F03FLAGS
           General user-specified options that are passed to the Fortran 03
           compiler. Note that this variable does not contain -I (or similar)
           include search path options that scons generates automatically from
           $F03PATH. See $_F03INCFLAGS below, for the variable that expands to
           those options. You only need to set $F03FLAGS if you need to define
           specific user options for Fortran 03 files. You should normally set
           the $FORTRANFLAGS variable, which specifies the user-specified
           options passed to the default Fortran compiler for all Fortran
           versions.

       _F03INCFLAGS
           An automatically-generated construction variable containing the
           Fortran 03 compiler command-line options for specifying directories
           to be searched for include files. The value of $_F03INCFLAGS is
           created by appending $INCPREFIX and $INCSUFFIX to the beginning and
           end of each directory in $F03PATH.

       F03PATH
           The list of directories that the Fortran 03 compiler will search
           for include directories. The implicit dependency scanner will
           search these directories for include files. Don't explicitly put
           include directory arguments in $F03FLAGS because the result will be
           non-portable and the directories will not be searched by the
           dependency scanner. Note: directory names in $F03PATH will be
           looked-up relative to the SConscript directory when they are used
           in a command. To force scons to look-up a directory relative to the
           root of the source tree use #: You only need to set $F03PATH if you
           need to define a specific include path for Fortran 03 files. You
           should normally set the $FORTRANPATH variable, which specifies the
           include path for the default Fortran compiler for all Fortran
           versions.

               env = Environment(F03PATH='#/include')

           The directory look-up can also be forced using the Dir() function:

               include = Dir('include')
               env = Environment(F03PATH=include)

           The directory list will be added to command lines through the
           automatically-generated $_F03INCFLAGS construction variable, which
           is constructed by appending the values of the $INCPREFIX and
           $INCSUFFIX construction variables to the beginning and end of each
           directory in $F03PATH. Any command lines you define that need the
           F03PATH directory list should include $_F03INCFLAGS:

               env = Environment(F03COM="my_compiler $_F03INCFLAGS -c -o $TARGET $SOURCE")

       F03PPCOM
           The command line used to compile a Fortran 03 source file to an
           object file after first running the file through the C
           preprocessor. Any options specified in the $F03FLAGS and $CPPFLAGS
           construction variables are included on this command line. You only
           need to set $F03PPCOM if you need to use a specific C-preprocessor
           command line for Fortran 03 files. You should normally set the
           $FORTRANPPCOM variable, which specifies the default C-preprocessor
           command line for all Fortran versions.

       F03PPCOMSTR
           If set, the string displayed when a Fortran 03 source file is
           compiled to an object file after first running the file through the
           C preprocessor. If not set, then $F03PPCOM or $FORTRANPPCOM (the
           command line) is displayed.

       F03PPFILESUFFIXES
           The list of file extensions for which the compilation +
           preprocessor pass for F03 dialect will be used. By default, this is
           empty.

       F08
           The Fortran 08 compiler. You should normally set the $FORTRAN
           variable, which specifies the default Fortran compiler for all
           Fortran versions. You only need to set $F08 if you need to use a
           specific compiler or compiler version for Fortran 08 files.

       F08COM
           The command line used to compile a Fortran 08 source file to an
           object file. You only need to set $F08COM if you need to use a
           specific command line for Fortran 08 files. You should normally set
           the $FORTRANCOM variable, which specifies the default command line
           for all Fortran versions.

       F08COMSTR
           If set, the string displayed when a Fortran 08 source file is
           compiled to an object file. If not set, then $F08COM or $FORTRANCOM
           (the command line) is displayed.

       F08FILESUFFIXES
           The list of file extensions for which the F08 dialect will be used.
           By default, this is ['.f08']

       F08FLAGS
           General user-specified options that are passed to the Fortran 08
           compiler. Note that this variable does not contain -I (or similar)
           include search path options that scons generates automatically from
           $F08PATH. See $_F08INCFLAGS below, for the variable that expands to
           those options. You only need to set $F08FLAGS if you need to define
           specific user options for Fortran 08 files. You should normally set
           the $FORTRANFLAGS variable, which specifies the user-specified
           options passed to the default Fortran compiler for all Fortran
           versions.

       _F08INCFLAGS
           An automatically-generated construction variable containing the
           Fortran 08 compiler command-line options for specifying directories
           to be searched for include files. The value of $_F08INCFLAGS is
           created by appending $INCPREFIX and $INCSUFFIX to the beginning and
           end of each directory in $F08PATH.

       F08PATH
           The list of directories that the Fortran 08 compiler will search
           for include directories. The implicit dependency scanner will
           search these directories for include files. Don't explicitly put
           include directory arguments in $F08FLAGS because the result will be
           non-portable and the directories will not be searched by the
           dependency scanner. Note: directory names in $F08PATH will be
           looked-up relative to the SConscript directory when they are used
           in a command. To force scons to look-up a directory relative to the
           root of the source tree use #: You only need to set $F08PATH if you
           need to define a specific include path for Fortran 08 files. You
           should normally set the $FORTRANPATH variable, which specifies the
           include path for the default Fortran compiler for all Fortran
           versions.

               env = Environment(F08PATH='#/include')

           The directory look-up can also be forced using the Dir() function:

               include = Dir('include')
               env = Environment(F08PATH=include)

           The directory list will be added to command lines through the
           automatically-generated $_F08INCFLAGS construction variable, which
           is constructed by appending the values of the $INCPREFIX and
           $INCSUFFIX construction variables to the beginning and end of each
           directory in $F08PATH. Any command lines you define that need the
           F08PATH directory list should include $_F08INCFLAGS:

               env = Environment(F08COM="my_compiler $_F08INCFLAGS -c -o $TARGET $SOURCE")

       F08PPCOM
           The command line used to compile a Fortran 08 source file to an
           object file after first running the file through the C
           preprocessor. Any options specified in the $F08FLAGS and $CPPFLAGS
           construction variables are included on this command line. You only
           need to set $F08PPCOM if you need to use a specific C-preprocessor
           command line for Fortran 08 files. You should normally set the
           $FORTRANPPCOM variable, which specifies the default C-preprocessor
           command line for all Fortran versions.

       F08PPCOMSTR
           If set, the string displayed when a Fortran 08 source file is
           compiled to an object file after first running the file through the
           C preprocessor. If not set, then $F08PPCOM or $FORTRANPPCOM (the
           command line) is displayed.

       F08PPFILESUFFIXES
           The list of file extensions for which the compilation +
           preprocessor pass for F08 dialect will be used. By default, this is
           empty.

       F77
           The Fortran 77 compiler. You should normally set the $FORTRAN
           variable, which specifies the default Fortran compiler for all
           Fortran versions. You only need to set $F77 if you need to use a
           specific compiler or compiler version for Fortran 77 files.

       F77COM
           The command line used to compile a Fortran 77 source file to an
           object file. You only need to set $F77COM if you need to use a
           specific command line for Fortran 77 files. You should normally set
           the $FORTRANCOM variable, which specifies the default command line
           for all Fortran versions.

       F77COMSTR
           If set, the string displayed when a Fortran 77 source file is
           compiled to an object file. If not set, then $F77COM or $FORTRANCOM
           (the command line) is displayed.

       F77FILESUFFIXES
           The list of file extensions for which the F77 dialect will be used.
           By default, this is ['.f77']

       F77FLAGS
           General user-specified options that are passed to the Fortran 77
           compiler. Note that this variable does not contain -I (or similar)
           include search path options that scons generates automatically from
           $F77PATH. See $_F77INCFLAGS below, for the variable that expands to
           those options. You only need to set $F77FLAGS if you need to define
           specific user options for Fortran 77 files. You should normally set
           the $FORTRANFLAGS variable, which specifies the user-specified
           options passed to the default Fortran compiler for all Fortran
           versions.

       _F77INCFLAGS
           An automatically-generated construction variable containing the
           Fortran 77 compiler command-line options for specifying directories
           to be searched for include files. The value of $_F77INCFLAGS is
           created by appending $INCPREFIX and $INCSUFFIX to the beginning and
           end of each directory in $F77PATH.

       F77PATH
           The list of directories that the Fortran 77 compiler will search
           for include directories. The implicit dependency scanner will
           search these directories for include files. Don't explicitly put
           include directory arguments in $F77FLAGS because the result will be
           non-portable and the directories will not be searched by the
           dependency scanner. Note: directory names in $F77PATH will be
           looked-up relative to the SConscript directory when they are used
           in a command. To force scons to look-up a directory relative to the
           root of the source tree use #: You only need to set $F77PATH if you
           need to define a specific include path for Fortran 77 files. You
           should normally set the $FORTRANPATH variable, which specifies the
           include path for the default Fortran compiler for all Fortran
           versions.

               env = Environment(F77PATH='#/include')

           The directory look-up can also be forced using the Dir() function:

               include = Dir('include')
               env = Environment(F77PATH=include)

           The directory list will be added to command lines through the
           automatically-generated $_F77INCFLAGS construction variable, which
           is constructed by appending the values of the $INCPREFIX and
           $INCSUFFIX construction variables to the beginning and end of each
           directory in $F77PATH. Any command lines you define that need the
           F77PATH directory list should include $_F77INCFLAGS:

               env = Environment(F77COM="my_compiler $_F77INCFLAGS -c -o $TARGET $SOURCE")

       F77PPCOM
           The command line used to compile a Fortran 77 source file to an
           object file after first running the file through the C
           preprocessor. Any options specified in the $F77FLAGS and $CPPFLAGS
           construction variables are included on this command line. You only
           need to set $F77PPCOM if you need to use a specific C-preprocessor
           command line for Fortran 77 files. You should normally set the
           $FORTRANPPCOM variable, which specifies the default C-preprocessor
           command line for all Fortran versions.

       F77PPCOMSTR
           If set, the string displayed when a Fortran 77 source file is
           compiled to an object file after first running the file through the
           C preprocessor. If not set, then $F77PPCOM or $FORTRANPPCOM (the
           command line) is displayed.

       F77PPFILESUFFIXES
           The list of file extensions for which the compilation +
           preprocessor pass for F77 dialect will be used. By default, this is
           empty.

       F90
           The Fortran 90 compiler. You should normally set the $FORTRAN
           variable, which specifies the default Fortran compiler for all
           Fortran versions. You only need to set $F90 if you need to use a
           specific compiler or compiler version for Fortran 90 files.

       F90COM
           The command line used to compile a Fortran 90 source file to an
           object file. You only need to set $F90COM if you need to use a
           specific command line for Fortran 90 files. You should normally set
           the $FORTRANCOM variable, which specifies the default command line
           for all Fortran versions.

       F90COMSTR
           If set, the string displayed when a Fortran 90 source file is
           compiled to an object file. If not set, then $F90COM or $FORTRANCOM
           (the command line) is displayed.

       F90FILESUFFIXES
           The list of file extensions for which the F90 dialect will be used.
           By default, this is ['.f90']

       F90FLAGS
           General user-specified options that are passed to the Fortran 90
           compiler. Note that this variable does not contain -I (or similar)
           include search path options that scons generates automatically from
           $F90PATH. See $_F90INCFLAGS below, for the variable that expands to
           those options. You only need to set $F90FLAGS if you need to define
           specific user options for Fortran 90 files. You should normally set
           the $FORTRANFLAGS variable, which specifies the user-specified
           options passed to the default Fortran compiler for all Fortran
           versions.

       _F90INCFLAGS
           An automatically-generated construction variable containing the
           Fortran 90 compiler command-line options for specifying directories
           to be searched for include files. The value of $_F90INCFLAGS is
           created by appending $INCPREFIX and $INCSUFFIX to the beginning and
           end of each directory in $F90PATH.

       F90PATH
           The list of directories that the Fortran 90 compiler will search
           for include directories. The implicit dependency scanner will
           search these directories for include files. Don't explicitly put
           include directory arguments in $F90FLAGS because the result will be
           non-portable and the directories will not be searched by the
           dependency scanner. Note: directory names in $F90PATH will be
           looked-up relative to the SConscript directory when they are used
           in a command. To force scons to look-up a directory relative to the
           root of the source tree use #: You only need to set $F90PATH if you
           need to define a specific include path for Fortran 90 files. You
           should normally set the $FORTRANPATH variable, which specifies the
           include path for the default Fortran compiler for all Fortran
           versions.

               env = Environment(F90PATH='#/include')

           The directory look-up can also be forced using the Dir() function:

               include = Dir('include')
               env = Environment(F90PATH=include)

           The directory list will be added to command lines through the
           automatically-generated $_F90INCFLAGS construction variable, which
           is constructed by appending the values of the $INCPREFIX and
           $INCSUFFIX construction variables to the beginning and end of each
           directory in $F90PATH. Any command lines you define that need the
           F90PATH directory list should include $_F90INCFLAGS:

               env = Environment(F90COM="my_compiler $_F90INCFLAGS -c -o $TARGET $SOURCE")

       F90PPCOM
           The command line used to compile a Fortran 90 source file to an
           object file after first running the file through the C
           preprocessor. Any options specified in the $F90FLAGS and $CPPFLAGS
           construction variables are included on this command line. You only
           need to set $F90PPCOM if you need to use a specific C-preprocessor
           command line for Fortran 90 files. You should normally set the
           $FORTRANPPCOM variable, which specifies the default C-preprocessor
           command line for all Fortran versions.

       F90PPCOMSTR
           If set, the string displayed when a Fortran 90 source file is
           compiled after first running the file through the C preprocessor.
           If not set, then $F90PPCOM or $FORTRANPPCOM (the command line) is
           displayed.

       F90PPFILESUFFIXES
           The list of file extensions for which the compilation +
           preprocessor pass for F90 dialect will be used. By default, this is
           empty.

       F95
           The Fortran 95 compiler. You should normally set the $FORTRAN
           variable, which specifies the default Fortran compiler for all
           Fortran versions. You only need to set $F95 if you need to use a
           specific compiler or compiler version for Fortran 95 files.

       F95COM
           The command line used to compile a Fortran 95 source file to an
           object file. You only need to set $F95COM if you need to use a
           specific command line for Fortran 95 files. You should normally set
           the $FORTRANCOM variable, which specifies the default command line
           for all Fortran versions.

       F95COMSTR
           If set, the string displayed when a Fortran 95 source file is
           compiled to an object file. If not set, then $F95COM or $FORTRANCOM
           (the command line) is displayed.

       F95FILESUFFIXES
           The list of file extensions for which the F95 dialect will be used.
           By default, this is ['.f95']

       F95FLAGS
           General user-specified options that are passed to the Fortran 95
           compiler. Note that this variable does not contain -I (or similar)
           include search path options that scons generates automatically from
           $F95PATH. See $_F95INCFLAGS below, for the variable that expands to
           those options. You only need to set $F95FLAGS if you need to define
           specific user options for Fortran 95 files. You should normally set
           the $FORTRANFLAGS variable, which specifies the user-specified
           options passed to the default Fortran compiler for all Fortran
           versions.

       _F95INCFLAGS
           An automatically-generated construction variable containing the
           Fortran 95 compiler command-line options for specifying directories
           to be searched for include files. The value of $_F95INCFLAGS is
           created by appending $INCPREFIX and $INCSUFFIX to the beginning and
           end of each directory in $F95PATH.

       F95PATH
           The list of directories that the Fortran 95 compiler will search
           for include directories. The implicit dependency scanner will
           search these directories for include files. Don't explicitly put
           include directory arguments in $F95FLAGS because the result will be
           non-portable and the directories will not be searched by the
           dependency scanner. Note: directory names in $F95PATH will be
           looked-up relative to the SConscript directory when they are used
           in a command. To force scons to look-up a directory relative to the
           root of the source tree use #: You only need to set $F95PATH if you
           need to define a specific include path for Fortran 95 files. You
           should normally set the $FORTRANPATH variable, which specifies the
           include path for the default Fortran compiler for all Fortran
           versions.

               env = Environment(F95PATH='#/include')

           The directory look-up can also be forced using the Dir() function:

               include = Dir('include')
               env = Environment(F95PATH=include)

           The directory list will be added to command lines through the
           automatically-generated $_F95INCFLAGS construction variable, which
           is constructed by appending the values of the $INCPREFIX and
           $INCSUFFIX construction variables to the beginning and end of each
           directory in $F95PATH. Any command lines you define that need the
           F95PATH directory list should include $_F95INCFLAGS:

               env = Environment(F95COM="my_compiler $_F95INCFLAGS -c -o $TARGET $SOURCE")

       F95PPCOM
           The command line used to compile a Fortran 95 source file to an
           object file after first running the file through the C
           preprocessor. Any options specified in the $F95FLAGS and $CPPFLAGS
           construction variables are included on this command line. You only
           need to set $F95PPCOM if you need to use a specific C-preprocessor
           command line for Fortran 95 files. You should normally set the
           $FORTRANPPCOM variable, which specifies the default C-preprocessor
           command line for all Fortran versions.

       F95PPCOMSTR
           If set, the string displayed when a Fortran 95 source file is
           compiled to an object file after first running the file through the
           C preprocessor. If not set, then $F95PPCOM or $FORTRANPPCOM (the
           command line) is displayed.

       F95PPFILESUFFIXES
           The list of file extensions for which the compilation +
           preprocessor pass for F95 dialect will be used. By default, this is
           empty.

       File
           A function that converts a string into a File instance relative to
           the target being built.

       FORTRAN
           The default Fortran compiler for all versions of Fortran.

       FORTRANCOM
           The command line used to compile a Fortran source file to an object
           file. By default, any options specified in the $FORTRANFLAGS,
           $CPPFLAGS, $_CPPDEFFLAGS, $_FORTRANMODFLAG, and $_FORTRANINCFLAGS
           construction variables are included on this command line.

       FORTRANCOMSTR
           If set, the string displayed when a Fortran source file is compiled
           to an object file. If not set, then $FORTRANCOM (the command line)
           is displayed.

       FORTRANFILESUFFIXES
           The list of file extensions for which the FORTRAN dialect will be
           used. By default, this is ['.f', '.for', '.ftn']

       FORTRANFLAGS
           General user-specified options that are passed to the Fortran
           compiler. Note that this variable does not contain -I (or similar)
           include or module search path options that scons generates
           automatically from $FORTRANPATH. See $_FORTRANINCFLAGS and
           $_FORTRANMODFLAG, below, for the variables that expand those
           options.

       _FORTRANINCFLAGS
           An automatically-generated construction variable containing the
           Fortran compiler command-line options for specifying directories to
           be searched for include files and module files. The value of
           $_FORTRANINCFLAGS is created by respectively prepending and
           appending $INCPREFIX and $INCSUFFIX to the beginning and end of
           each directory in $FORTRANPATH.

       FORTRANMODDIR
           Directory location where the Fortran compiler should place any
           module files it generates. This variable is empty, by default. Some
           Fortran compilers will internally append this directory in the
           search path for module files, as well.

       FORTRANMODDIRPREFIX
           The prefix used to specify a module directory on the Fortran
           compiler command line. This will be prepended to the beginning of
           the directory in the $FORTRANMODDIR construction variables when the
           $_FORTRANMODFLAG variables is automatically generated.

       FORTRANMODDIRSUFFIX
           The suffix used to specify a module directory on the Fortran
           compiler command line. This will be appended to the end of the
           directory in the $FORTRANMODDIR construction variables when the
           $_FORTRANMODFLAG variables is automatically generated.

       _FORTRANMODFLAG
           An automatically-generated construction variable containing the
           Fortran compiler command-line option for specifying the directory
           location where the Fortran compiler should place any module files
           that happen to get generated during compilation. The value of
           $_FORTRANMODFLAG is created by respectively prepending and
           appending $FORTRANMODDIRPREFIX and $FORTRANMODDIRSUFFIX to the
           beginning and end of the directory in $FORTRANMODDIR.

       FORTRANMODPREFIX
           The module file prefix used by the Fortran compiler. SCons assumes
           that the Fortran compiler follows the quasi-standard naming
           convention for module files of module_name.mod. As a result, this
           variable is left empty, by default. For situations in which the
           compiler does not necessarily follow the normal convention, the
           user may use this variable. Its value will be appended to every
           module file name as scons attempts to resolve dependencies.

       FORTRANMODSUFFIX
           The module file suffix used by the Fortran compiler. SCons assumes
           that the Fortran compiler follows the quasi-standard naming
           convention for module files of module_name.mod. As a result, this
           variable is set to ".mod", by default. For situations in which the
           compiler does not necessarily follow the normal convention, the
           user may use this variable. Its value will be appended to every
           module file name as scons attempts to resolve dependencies.

       FORTRANPATH
           The list of directories that the Fortran compiler will search for
           include files and (for some compilers) module files. The Fortran
           implicit dependency scanner will search these directories for
           include files (but not module files since they are autogenerated
           and, as such, may not actually exist at the time the scan takes
           place). Don't explicitly put include directory arguments in
           FORTRANFLAGS because the result will be non-portable and the
           directories will not be searched by the dependency scanner. Note:
           directory names in FORTRANPATH will be looked-up relative to the
           SConscript directory when they are used in a command. To force
           scons to look-up a directory relative to the root of the source
           tree use #:

               env = Environment(FORTRANPATH='#/include')

           The directory look-up can also be forced using the Dir() function:

               include = Dir('include')
               env = Environment(FORTRANPATH=include)

           The directory list will be added to command lines through the
           automatically-generated $_FORTRANINCFLAGS construction variable,
           which is constructed by respectively prepending and appending the
           values of the $INCPREFIX and $INCSUFFIX construction variables to
           the beginning and end of each directory in $FORTRANPATH. Any
           command lines you define that need the FORTRANPATH directory list
           should include $_FORTRANINCFLAGS:

               env = Environment(FORTRANCOM="my_compiler $_FORTRANINCFLAGS -c -o $TARGET $SOURCE")

       FORTRANPPCOM
           The command line used to compile a Fortran source file to an object
           file after first running the file through the C preprocessor. By
           default, any options specified in the $FORTRANFLAGS, $CPPFLAGS,
           $_CPPDEFFLAGS, $_FORTRANMODFLAG, and $_FORTRANINCFLAGS construction
           variables are included on this command line.

       FORTRANPPCOMSTR
           If set, the string displayed when a Fortran source file is compiled
           to an object file after first running the file through the C
           preprocessor. If not set, then $FORTRANPPCOM (the command line) is
           displayed.

       FORTRANPPFILESUFFIXES
           The list of file extensions for which the compilation +
           preprocessor pass for FORTRAN dialect will be used. By default,
           this is ['.fpp', '.FPP']

       FORTRANSUFFIXES
           The list of suffixes of files that will be scanned for Fortran
           implicit dependencies (INCLUDE lines and USE statements). The
           default list is:

               [".f", ".F", ".for", ".FOR", ".ftn", ".FTN", ".fpp", ".FPP",
               ".f77", ".F77", ".f90", ".F90", ".f95", ".F95"]

       FRAMEWORKPATH
           On Mac OS X with gcc, a list containing the paths to search for
           frameworks. Used by the compiler to find framework-style includes
           like #include <Fmwk/Header.h>. Used by the linker to find
           user-specified frameworks when linking (see $FRAMEWORKS). For
           example:

               env.AppendUnique(FRAMEWORKPATH='#myframeworkdir')


           will add

               ... -Fmyframeworkdir


           to the compiler and linker command lines.

       _FRAMEWORKPATH
           On Mac OS X with gcc, an automatically-generated construction
           variable containing the linker command-line options corresponding
           to $FRAMEWORKPATH.

       FRAMEWORKPATHPREFIX
           On Mac OS X with gcc, the prefix to be used for the FRAMEWORKPATH
           entries. (see $FRAMEWORKPATH). The default value is -F.

       FRAMEWORKPREFIX
           On Mac OS X with gcc, the prefix to be used for linking in
           frameworks (see $FRAMEWORKS). The default value is -framework.

       FRAMEWORKS
           On Mac OS X with gcc, a list of the framework names to be linked
           into a program or shared library or bundle. The default value is
           the empty list. For example:

               env.AppendUnique(FRAMEWORKS=Split('System Cocoa SystemConfiguration'))


       _FRAMEWORKS
           On Mac OS X with gcc, an automatically-generated construction
           variable containing the linker command-line options for linking
           with FRAMEWORKS.

       FRAMEWORKSFLAGS
           On Mac OS X with gcc, general user-supplied frameworks options to
           be added at the end of a command line building a loadable module.
           (This has been largely superseded by the $FRAMEWORKPATH,
           $FRAMEWORKPATHPREFIX, $FRAMEWORKPREFIX and $FRAMEWORKS variables
           described above.)

       GS
           The Ghostscript program used to, for example, convert PostScript to
           PDF files.

       GSCOM
           The full Ghostscript command line used for the conversion process.
           Its default value is "$GS $GSFLAGS -sOutputFile=$TARGET $SOURCES".

       GSCOMSTR
           The string displayed when Ghostscript is called for the conversion
           process. If this is not set (the default), then $GSCOM (the command
           line) is displayed.

       GSFLAGS
           General options passed to the Ghostscript program, when converting
           PostScript to PDF files for example. Its default value is
           "-dNOPAUSE -dBATCH -sDEVICE=pdfwrite"

       HOST_ARCH
           The name of the host hardware architecture used to create the
           Environment. If a platform is specified when creating the
           Environment, then that Platform's logic will handle setting this
           value. This value is immutable, and should not be changed by the
           user after the Environment is initialized. Currently only set for
           Win32.

           Sets the host architecture for the Visual C++ compiler. If not set,
           default to the detected host architecture: note that this may
           depend on the python you are using. This variable must be passed as
           an argument to the Environment() constructor; setting it later has
           no effect.

           Valid values are the same as for $TARGET_ARCH.

           This is currently only used on Windows, but in the future it may be
           used on other OSes as well.

       HOST_OS
           The name of the host operating system used to create the
           Environment. If a platform is specified when creating the
           Environment, then that Platform's logic will handle setting this
           value. This value is immutable, and should not be changed by the
           user after the Environment is initialized. Currently only set for
           Win32.

       IDLSUFFIXES
           The list of suffixes of files that will be scanned for IDL implicit
           dependencies (#include or import lines). The default list is:

               [".idl", ".IDL"]

       IMPLIBNOVERSIONSYMLINKS
           Used to override $SHLIBNOVERSIONSYMLINKS/$LDMODULENOVERSIONSYMLINKS
           when creating versioned import library for a shared
           library/loadable module. If not defined, then
           $SHLIBNOVERSIONSYMLINKS/$LDMODULENOVERSIONSYMLINKS is used to
           determine whether to disable symlink generation or not.

       IMPLIBPREFIX
           The prefix used for import library names. For example, cygwin uses
           import libraries (libfoo.dll.a) in pair with dynamic libraries
           (cygfoo.dll). The cyglink linker sets $IMPLIBPREFIX to 'lib' and
           $SHLIBPREFIX to 'cyg'.

       IMPLIBSUFFIX
           The suffix used for import library names. For example, cygwin uses
           import libraries (libfoo.dll.a) in pair with dynamic libraries
           (cygfoo.dll). The cyglink linker sets $IMPLIBSUFFIX to '.dll.a' and
           $SHLIBSUFFIX to '.dll'.

       IMPLIBVERSION
           Used to override $SHLIBVERSION/$LDMODULEVERSION when generating
           versioned import library for a shared library/loadable module. If
           undefined, the $SHLIBVERSION/$LDMODULEVERSION is used to determine
           the version of versioned import library.

       IMPLICIT_COMMAND_DEPENDENCIES
           Controls whether or not SCons will add implicit dependencies for
           the commands executed to build targets.

           By default, SCons will add to each target an implicit dependency on
           the command represented by the first argument of any command line
           it executes (which is typically the command itself). By setting
           such a dependency, SCons can determine that a target should be
           rebuilt if the command changes, such as when a compiler is upgraded
           to a new version. The specific file for the dependency is found by
           searching the PATH variable in the ENV dictionary in the
           construction environment used to execute the command. The default
           is the same as setting the construction variable
           $IMPLICIT_COMMAND_DEPENDENCIES to a True-like value ("true", "yes",
           or "1" - but not a number greater than one, as that has a different
           meaning).

           Action strings can be segmented by the use of an AND operator, &&.
           In a segemented string, each segment is a separate "command line",
           these are run sequentially until one fails or the entire sequence
           has been executed. If an action string is segmented, then the
           selected behavior of $IMPLICIT_COMMAND_DEPENDENCIES is applied to
           each segment.

           If $IMPLICIT_COMMAND_DEPENDENCIES is set to a False-like value
           ("none", "false", "no", "0", etc.), then the implicit dependency
           will not be added to the targets built with that construction
           environment.

           If $IMPLICIT_COMMAND_DEPENDENCIES is set to "2" or higher, then
           that number of arguments in the command line will be scanned for
           relative or absolute paths. If any are present, they will be added
           as implicit dependencies to the targets built with that
           construction environment. The first argument in the command line
           will be searched for using the PATH variable in the ENV dictionary
           in the construction environment used to execute the command. The
           other arguments will only be found if they are absolute paths or
           valid paths relative to the working directory.

           If $IMPLICIT_COMMAND_DEPENDENCIES is set to "all", then all
           arguments in the command line will be scanned for relative or
           absolute paths. If any are present, they will be added as implicit
           dependencies to the targets built with that construction
           environment. The first argument in the command line will be
           searched for using the PATH variable in the ENV dictionary in the
           construction environment used to execute the command. The other
           arguments will only be found if they are absolute paths or valid
           paths relative to the working directory.

               env = Environment(IMPLICIT_COMMAND_DEPENDENCIES=False)

       INCPREFIX
           The prefix used to specify an include directory on the C compiler
           command line. This will be prepended to each directory in the
           $CPPPATH and $FORTRANPATH construction variables when the
           $_CPPINCFLAGS and $_FORTRANINCFLAGS variables are automatically
           generated.

       INCSUFFIX
           The suffix used to specify an include directory on the C compiler
           command line. This will be appended to each directory in the
           $CPPPATH and $FORTRANPATH construction variables when the
           $_CPPINCFLAGS and $_FORTRANINCFLAGS variables are automatically
           generated.

       INSTALL
           A function to be called to install a file into a destination file
           name. The default function copies the file into the destination
           (and sets the destination file's mode and permission bits to match
           the source file's). The function takes the following arguments:

               def install(dest, source, env):


           dest is the path name of the destination file.  source is the path
           name of the source file.  env is the construction environment (a
           dictionary of construction values) in force for this file
           installation.

       INSTALLSTR
           The string displayed when a file is installed into a destination
           file name. The default is:

               Install file: "$SOURCE" as "$TARGET"

       INTEL_C_COMPILER_VERSION
           Set by the intelc Tool to the major version number of the Intel C
           compiler selected for use.

       JAR
           The Java archive tool.

       JARCHDIR
           The directory to which the Java archive tool should change (using
           the -C option).

       JARCOM
           The command line used to call the Java archive tool.

       JARCOMSTR
           The string displayed when the Java archive tool is called If this
           is not set, then $JARCOM (the command line) is displayed.

               env = Environment(JARCOMSTR="JARchiving $SOURCES into $TARGET")

       JARFLAGS
           General options passed to the Java archive tool. By default this is
           set to cf to create the necessary jar file.

       JARSUFFIX
           The suffix for Java archives: .jar by default.

       JAVABOOTCLASSPATH
           Specifies the list of directories that will be added to the javac
           command line via the -bootclasspath option. The individual
           directory names will be separated by the operating system's path
           separate character (: on UNIX/Linux/POSIX, ; on Windows).

       JAVAC
           The Java compiler.

       JAVACCOM
           The command line used to compile a directory tree containing Java
           source files to corresponding Java class files. Any options
           specified in the $JAVACFLAGS construction variable are included on
           this command line.

       JAVACCOMSTR
           The string displayed when compiling a directory tree of Java source
           files to corresponding Java class files. If this is not set, then
           $JAVACCOM (the command line) is displayed.

               env = Environment(JAVACCOMSTR="Compiling class files $TARGETS from $SOURCES")


       JAVACFLAGS
           General options that are passed to the Java compiler.

       JAVACLASSDIR
           The directory in which Java class files may be found. This is
           stripped from the beginning of any Java .class file names supplied
           to the JavaH builder.

       JAVACLASSPATH
           Specifies the list of directories that will be searched for Java
           .class file. The directories in this list will be added to the
           javac and javah command lines via the -classpath option. The
           individual directory names will be separated by the operating
           system's path separate character (: on UNIX/Linux/POSIX, ; on
           Windows).

           Note that this currently just adds the specified directory via the
           -classpath option.  SCons does not currently search the
           $JAVACLASSPATH directories for dependency .class files.

       JAVACLASSSUFFIX
           The suffix for Java class files; .class by default.

       JAVAH
           The Java generator for C header and stub files.

       JAVAHCOM
           The command line used to generate C header and stub files from Java
           classes. Any options specified in the $JAVAHFLAGS construction
           variable are included on this command line.

       JAVAHCOMSTR
           The string displayed when C header and stub files are generated
           from Java classes. If this is not set, then $JAVAHCOM (the command
           line) is displayed.

               env = Environment(JAVAHCOMSTR="Generating header/stub file(s) $TARGETS from $SOURCES")

       JAVAHFLAGS
           General options passed to the C header and stub file generator for
           Java classes.

       JAVAINCLUDES
           Include path for Java header files (such as jni.h)

       JAVASOURCEPATH
           Specifies the list of directories that will be searched for input
           .java file. The directories in this list will be added to the javac
           command line via the -sourcepath option. The individual directory
           names will be separated by the operating system's path separate
           character (: on UNIX/Linux/POSIX, ; on Windows).

           Note that this currently just adds the specified directory via the
           -sourcepath option.  SCons does not currently search the
           $JAVASOURCEPATH directories for dependency .java files.

       JAVASUFFIX
           The suffix for Java files; .java by default.

       JAVAVERSION
           Specifies the Java version being used by the Java builder. This is
           not currently used to select one version of the Java compiler vs.
           another. Instead, you should set this to specify the version of
           Java supported by your javac compiler. The default is 1.4.

           This is sometimes necessary because Java 1.5 changed the file names
           that are created for nested anonymous inner classes, which can
           cause a mismatch with the files that SCons expects will be
           generated by the javac compiler. Setting $JAVAVERSION to 1.5 (or
           1.6, as appropriate) can make SCons realize that a Java 1.5 or 1.6
           build is actually up to date.

       LATEX
           The LaTeX structured formatter and typesetter.

       LATEXCOM
           The command line used to call the LaTeX structured formatter and
           typesetter.

       LATEXCOMSTR
           The string displayed when calling the LaTeX structured formatter
           and typesetter. If this is not set, then $LATEXCOM (the command
           line) is displayed.

               env = Environment(LATEXCOMSTR = "Building $TARGET from LaTeX input $SOURCES")

       LATEXFLAGS
           General options passed to the LaTeX structured formatter and
           typesetter.

       LATEXRETRIES
           The maximum number of times that LaTeX will be re-run if the .log
           generated by the $LATEXCOM command indicates that there are
           undefined references. The default is to try to resolve undefined
           references by re-running LaTeX up to three times.

       LATEXSUFFIXES
           The list of suffixes of files that will be scanned for LaTeX
           implicit dependencies (\include or \import files). The default list
           is:

               [".tex", ".ltx", ".latex"]

       LDMODULE
           The linker for building loadable modules. By default, this is the
           same as $SHLINK.

       LDMODULECOM
           The command line for building loadable modules. On Mac OS X, this
           uses the $LDMODULE, $LDMODULEFLAGS and $FRAMEWORKSFLAGS variables.
           On other systems, this is the same as $SHLINK.

       LDMODULECOMSTR
           If set, the string displayed when building loadable modules. If not
           set, then $LDMODULECOM (the command line) is displayed.

       LDMODULEEMITTER
           Contains the emitter specification for the LoadableModule builder.
           The manpage section "Builder Objects" contains general information
           on specifying emitters.

       LDMODULEFLAGS
           General user options passed to the linker for building loadable
           modules.

       LDMODULENOVERSIONSYMLINKS
           Instructs the LoadableModule builder to not automatically create
           symlinks for versioned modules. Defaults to $SHLIBNOVERSIONSYMLINKS

       LDMODULEPREFIX
           The prefix used for loadable module file names. On Mac OS X, this
           is null; on other systems, this is the same as $SHLIBPREFIX.

       _LDMODULESONAME
           A macro that automatically generates loadable module's SONAME based
           on $TARGET, $LDMODULEVERSION and $LDMODULESUFFIX. Used by
           LoadableModule builder when the linker tool supports SONAME (e.g.
           gnulink).

       LDMODULESUFFIX
           The suffix used for loadable module file names. On Mac OS X, this
           is null; on other systems, this is the same as $SHLIBSUFFIX.

       LDMODULEVERSION
           When this construction variable is defined, a versioned loadable
           module is created by LoadableModule builder. This activates the
           $_LDMODULEVERSIONFLAGS and thus modifies the $LDMODULECOM as
           required, adds the version number to the library name, and creates
           the symlinks that are needed.  $LDMODULEVERSION versions should
           exist in the same format as $SHLIBVERSION.

       _LDMODULEVERSIONFLAGS
           This macro automatically introduces extra flags to $LDMODULECOM
           when building versioned LoadableModule (that is when
           $LDMODULEVERSION is set).  _LDMODULEVERSIONFLAGS usually adds
           $SHLIBVERSIONFLAGS and some extra dynamically generated options
           (such as -Wl,-soname=$_LDMODULESONAME). It is unused by plain
           (unversioned) loadable modules.

       LDMODULEVERSIONFLAGS
           Extra flags added to $LDMODULECOM when building versioned
           LoadableModule. These flags are only used when $LDMODULEVERSION is
           set.

       LEX
           The lexical analyzer generator.

       LEXCOM
           The command line used to call the lexical analyzer generator to
           generate a source file.

       LEXCOMSTR
           The string displayed when generating a source file using the
           lexical analyzer generator. If this is not set, then $LEXCOM (the
           command line) is displayed.

               env = Environment(LEXCOMSTR = "Lex'ing $TARGET from $SOURCES")

       LEXFLAGS
           General options passed to the lexical analyzer generator.

       LEXUNISTD
           Used only on windows environments to set a lex flag to prevent
           'unistd.h' from being included. The default value is '--nounistd'.

       _LIBDIRFLAGS
           An automatically-generated construction variable containing the
           linker command-line options for specifying directories to be
           searched for library. The value of $_LIBDIRFLAGS is created by
           respectively prepending and appending $LIBDIRPREFIX and
           $LIBDIRSUFFIX to each directory in $LIBPATH.

       LIBDIRPREFIX
           The prefix used to specify a library directory on the linker
           command line. This will be prepended to each directory in the
           $LIBPATH construction variable when the $_LIBDIRFLAGS variable is
           automatically generated.

       LIBDIRSUFFIX
           The suffix used to specify a library directory on the linker
           command line. This will be appended to each directory in the
           $LIBPATH construction variable when the $_LIBDIRFLAGS variable is
           automatically generated.

       LIBEMITTER
           Contains the emitter specification for the StaticLibrary builder.
           The manpage section "Builder Objects" contains general information
           on specifying emitters.

       _LIBFLAGS
           An automatically-generated construction variable containing the
           linker command-line options for specifying libraries to be linked
           with the resulting target. The value of $_LIBFLAGS is created by
           respectively prepending and appending $LIBLINKPREFIX and
           $LIBLINKSUFFIX to each filename in $LIBS.

       LIBLINKPREFIX
           The prefix used to specify a library to link on the linker command
           line. This will be prepended to each library in the $LIBS
           construction variable when the $_LIBFLAGS variable is automatically
           generated.

       LIBLINKSUFFIX
           The suffix used to specify a library to link on the linker command
           line. This will be appended to each library in the $LIBS
           construction variable when the $_LIBFLAGS variable is automatically
           generated.

       LIBPATH
           The list of directories that will be searched for libraries
           specified by the $LIBS construction variable.  $LIBPATH should be a
           list of path strings, or a single string, not a pathname list
           joined by Python's os.sep.

           Do not put library search directives directly into $LINKFLAGS or
           $SHLINKFLAGS as the result will be non-portable.

           Note: directory names in $LIBPATH will be looked-up relative to the
           directory of the SConscript file when they are used in a command.
           To force scons to look-up a directory relative to the root of the
           source tree use the # prefix:

               env = Environment(LIBPATH='#/libs')

           The directory look-up can also be forced using the Dir function:

               libs = Dir('libs')
               env = Environment(LIBPATH=libs)

           The directory list will be added to command lines through the
           automatically-generated $_LIBDIRFLAGS construction variable, which
           is constructed by respectively prepending and appending the values
           of the $LIBDIRPREFIX and $LIBDIRSUFFIX construction variables to
           each directory in $LIBPATH. Any command lines you define that need
           the $LIBPATH directory list should include $_LIBDIRFLAGS:

               env = Environment(LINKCOM="my_linker $_LIBDIRFLAGS $_LIBFLAGS -o $TARGET $SOURCE")

       LIBPREFIX
           The prefix used for (static) library file names. A default value is
           set for each platform (posix, win32, os2, etc.), but the value is
           overridden by individual tools (ar, mslib, sgiar, sunar, tlib,
           etc.) to reflect the names of the libraries they create.

       LIBPREFIXES
           A list of all legal prefixes for library file names. When searching
           for library dependencies, SCons will look for files with these
           prefixes, the base library name, and suffixes from the $LIBSUFFIXES
           list.

       LIBS
           A list of one or more libraries that will be added to the link line
           for linking with any executable program, shared library, or
           loadable module created by the construction environment or
           override.

           String-valued library names should include only the library base
           names, without prefixes such as lib or suffixes such as .so or
           .dll. The library list will be added to command lines through the
           automatically-generated $_LIBFLAGS construction variable which is
           constructed by respectively prepending and appending the values of
           the $LIBLINKPREFIX and $LIBLINKSUFFIX construction variables to
           each library name in $LIBS. Library name strings should not include
           a path component, instead the compiler will be directed to look for
           libraries in the paths specified by $LIBPATH.

           Any command lines you define that need the $LIBS library list
           should include $_LIBFLAGS:

               env = Environment(LINKCOM="my_linker $_LIBDIRFLAGS $_LIBFLAGS -o $TARGET $SOURCE")

           If you add a File object to the $LIBS list, the name of that file
           will be added to $_LIBFLAGS, and thus to the link line, as-is,
           without $LIBLINKPREFIX or $LIBLINKSUFFIX. For example:

               env.Append(LIBS=File('/tmp/mylib.so'))

           In all cases, scons will add dependencies from the executable
           program to all the libraries in this list.

       LIBSUFFIX
           The suffix used for (static) library file names. A default value is
           set for each platform (posix, win32, os2, etc.), but the value is
           overridden by individual tools (ar, mslib, sgiar, sunar, tlib,
           etc.) to reflect the names of the libraries they create.

       LIBSUFFIXES
           A list of all legal suffixes for library file names. When searching
           for library dependencies, SCons will look for files with prefixes
           from the $LIBPREFIXES list, the base library name, and these
           suffixes.

       LICENSE
           The abbreviated name, preferably the SPDX code, of the license
           under which this project is released (GPL-3.0, LGPL-2.1,
           BSD-2-Clause etc.). See
           http://www.opensource.org/licenses/alphabetical[4] for a list of
           license names and SPDX codes.

           See the Package builder.

       LINESEPARATOR
           The separator used by the Substfile and Textfile builders. This
           value is used between sources when constructing the target. It
           defaults to the current system line separator.

       LINGUAS_FILE
           The $LINGUAS_FILE defines file(s) containing list of additional
           linguas to be processed by POInit, POUpdate or MOFiles builders. It
           also affects Translate builder. If the variable contains a string,
           it defines name of the list file. The $LINGUAS_FILE may be a list
           of file names as well. If $LINGUAS_FILE is set to True (or non-zero
           numeric value), the list will be read from default file named
           LINGUAS.

       LINK
           The linker. See also $SHLINK for linking shared objects.

           On POSIX systems (those using the link tool), you should normally
           not change this value as it defaults to a "smart" linker tool which
           selects a compiler driver matching the type of source files in use.
           So for example, if you set $CXX to a specific compiler name, and
           are compiling C++ sources, the smartlink function will
           automatically select the same compiler for linking.

       LINKCOM
           The command line used to link object files into an executable. See
           also $SHLINKCOM for linking shared objects.

       LINKCOMSTR
           If set, the string displayed when object files are linked into an
           executable. If not set, then $LINKCOM (the command line) is
           displayed. See also $SHLINKCOMSTR. for linking shared objects.

               env = Environment(LINKCOMSTR = "Linking $TARGET")

       LINKFLAGS
           General user options passed to the linker. Note that this variable
           should not contain -l (or similar) options for linking with the
           libraries listed in $LIBS, nor -L (or similar) library search path
           options that scons generates automatically from $LIBPATH. See
           $_LIBFLAGS above, for the variable that expands to library-link
           options, and $_LIBDIRFLAGS above, for the variable that expands to
           library search path options. See also $SHLINKFLAGS. for linking
           shared objects.

       M4
           The M4 macro preprocessor.

       M4COM
           The command line used to pass files through the M4 macro
           preprocessor.

       M4COMSTR
           The string displayed when a file is passed through the M4 macro
           preprocessor. If this is not set, then $M4COM (the command line) is
           displayed.

       M4FLAGS
           General options passed to the M4 macro preprocessor.

       MAKEINDEX
           The makeindex generator for the TeX formatter and typesetter and
           the LaTeX structured formatter and typesetter.

       MAKEINDEXCOM
           The command line used to call the makeindex generator for the TeX
           formatter and typesetter and the LaTeX structured formatter and
           typesetter.

       MAKEINDEXCOMSTR
           The string displayed when calling the makeindex generator for the
           TeX formatter and typesetter and the LaTeX structured formatter and
           typesetter. If this is not set, then $MAKEINDEXCOM (the command
           line) is displayed.

       MAKEINDEXFLAGS
           General options passed to the makeindex generator for the TeX
           formatter and typesetter and the LaTeX structured formatter and
           typesetter.

       MAXLINELENGTH
           The maximum number of characters allowed on an external command
           line. On Win32 systems, link lines longer than this many characters
           are linked via a temporary file name.

       MIDL
           The Microsoft IDL compiler.

       MIDLCOM
           The command line used to pass files to the Microsoft IDL compiler.

       MIDLCOMSTR
           The string displayed when the Microsoft IDL compiler is called. If
           this is not set, then $MIDLCOM (the command line) is displayed.

       MIDLFLAGS
           General options passed to the Microsoft IDL compiler.

       MOSUFFIX
           Suffix used for MO files (default: '.mo'). See msgfmt tool and
           MOFiles builder.

       MSGFMT
           Absolute path to msgfmt(1) binary, found by Detect(). See msgfmt
           tool and MOFiles builder.

       MSGFMTCOM
           Complete command line to run msgfmt(1) program. See msgfmt tool and
           MOFiles builder.

       MSGFMTCOMSTR
           String to display when msgfmt(1) is invoked (default: '', which
           means ``print $MSGFMTCOM''). See msgfmt tool and MOFiles builder.

       MSGFMTFLAGS
           Additional flags to msgfmt(1). See msgfmt tool and MOFiles builder.

       MSGINIT
           Path to msginit(1) program (found via Detect()). See msginit tool
           and POInit builder.

       MSGINITCOM
           Complete command line to run msginit(1) program. See msginit tool
           and POInit builder.

       MSGINITCOMSTR
           String to display when msginit(1) is invoked (default: '', which
           means ``print $MSGINITCOM''). See msginit tool and POInit builder.

       MSGINITFLAGS
           List of additional flags to msginit(1) (default: []). See msginit
           tool and POInit builder.

       _MSGINITLOCALE
           Internal ``macro''. Computes locale (language) name based on target
           filename (default: '${TARGET.filebase}').

           See msginit tool and POInit builder.

       MSGMERGE
           Absolute path to msgmerge(1) binary as found by Detect(). See
           msgmerge tool and POUpdate builder.

       MSGMERGECOM
           Complete command line to run msgmerge(1) command. See msgmerge tool
           and POUpdate builder.

       MSGMERGECOMSTR
           String to be displayed when msgmerge(1) is invoked (default: '',
           which means ``print $MSGMERGECOM''). See msgmerge tool and POUpdate
           builder.

       MSGMERGEFLAGS
           Additional flags to msgmerge(1) command. See msgmerge tool and
           POUpdate builder.

       MSSDK_DIR
           The directory containing the Microsoft SDK (either Platform SDK or
           Windows SDK) to be used for compilation.

       MSSDK_VERSION
           The version string of the Microsoft SDK (either Platform SDK or
           Windows SDK) to be used for compilation. Supported versions include
           6.1, 6.0A, 6.0, 2003R2 and 2003R1.

       MSVC_BATCH
           When set to any true value, specifies that SCons should batch
           compilation of object files when calling the Microsoft Visual C/C++
           compiler. All compilations of source files from the same source
           directory that generate target files in a same output directory and
           were configured in SCons using the same construction environment
           will be built in a single call to the compiler. Only source files
           that have changed since their object files were built will be
           passed to each compiler invocation (via the $CHANGED_SOURCES
           construction variable). Any compilations where the object (target)
           file base name (minus the .obj) does not match the source file base
           name will be compiled separately.

       MSVC_USE_SCRIPT
           Use a batch script to set up the Microsoft Visual C++ compiler.

           If set to the name of a Visual Studio .bat file (e.g.  vcvars.bat),
           SCons will run that batch file instead of the auto-detected one,
           and extract the relevant variables from the result (typically
           %INCLUDE%, %LIB%, and %PATH%) for supplying to the build. This can
           be useful to force the use of a compiler version that SCons does
           not detect.

           Setting $MSVC_USE_SCRIPT to None bypasses the Visual Studio
           autodetection entirely; use this if you are running SCons in a
           Visual Studio cmd window and importing the shell's environment
           variables - that is, if you are sure everything is set correctly
           already and you don't want SCons to change anything.


           $MSVC_USE_SCRIPT overrides $MSVC_VERSION and $TARGET_ARCH.

       MSVC_UWP_APP
           Build libraries for a Universal Windows Platform (UWP) Application.

           If $MSVC_UWP_APP is set, the Visual C++ environment will be set up
           to point to the Windows Store compatible libraries and Visual C++
           runtimes. In doing so, any libraries that are built will be able to
           be used in a UWP App and published to the Windows Store. This flag
           will only have an effect with Visual Studio 2015 or later. This
           variable must be passed as an argument to the Environment()
           constructor; setting it later has no effect.

           Valid values are '1' or '0'

       MSVC_VERSION
           Sets the preferred version of Microsoft Visual C/C++ to use.

           If $MSVC_VERSION is not set, SCons will (by default) select the
           latest version of Visual C/C++ installed on your system. If the
           specified version isn't installed, tool initialization will fail.
           This variable must be passed as an argument to the Environment
           constructor; setting it later has no effect.

           Valid values for Windows are 14.2, 14.1, 14.1Exp, 14.0, 14.0Exp,
           12.0, 12.0Exp, 11.0, 11.0Exp, 10.0, 10.0Exp, 9.0, 9.0Exp, 8.0,
           8.0Exp, 7.1, 7.0, and 6.0. Versions ending in Exp refer to
           "Express" or "Express for Desktop" editions.

       MSVS
           When the Microsoft Visual Studio tools are initialized, they set up
           this dictionary with the following keys:

           VERSION
               the version of MSVS being used (can be set via $MSVS_VERSION)

           VERSIONS
               the available versions of MSVS installed

           VCINSTALLDIR
               installed directory of Visual C++

           VSINSTALLDIR
               installed directory of Visual Studio

           FRAMEWORKDIR
               installed directory of the .NET framework

           FRAMEWORKVERSIONS
               list of installed versions of the .NET framework, sorted latest
               to oldest.

           FRAMEWORKVERSION
               latest installed version of the .NET framework

           FRAMEWORKSDKDIR
               installed location of the .NET SDK.

           PLATFORMSDKDIR
               installed location of the Platform SDK.

           PLATFORMSDK_MODULES
               dictionary of installed Platform SDK modules, where the
               dictionary keys are keywords for the various modules, and the
               values are 2-tuples where the first is the release date, and
               the second is the version number.

           If a value is not set, it was not available in the registry.

       MSVS_ARCH
           Sets the architecture for which the generated project(s) should
           build.

           The default value is x86.  amd64 is also supported by SCons for
           most Visual Studio versions. Since Visual Studio 2015 arm is
           supported, and since Visual Studio 2017 arm64 is supported. Trying
           to set $MSVS_ARCH to an architecture that's not supported for a
           given Visual Studio version will generate an error.

       MSVS_PROJECT_GUID
           The string placed in a generated Microsoft Visual Studio project
           file as the value of the ProjectGUID attribute. There is no default
           value. If not defined, a new GUID is generated.

       MSVS_SCC_AUX_PATH
           The path name placed in a generated Microsoft Visual Studio project
           file as the value of the SccAuxPath attribute if the
           MSVS_SCC_PROVIDER construction variable is also set. There is no
           default value.

       MSVS_SCC_CONNECTION_ROOT
           The root path of projects in your SCC workspace, i.e the path under
           which all project and solution files will be generated. It is used
           as a reference path from which the relative paths of the generated
           Microsoft Visual Studio project and solution files are computed.
           The relative project file path is placed as the value of the
           SccLocalPath attribute of the project file and as the values of the
           SccProjectFilePathRelativizedFromConnection[i] (where [i] ranges
           from 0 to the number of projects in the solution) attributes of the
           GlobalSection(SourceCodeControl) section of the Microsoft Visual
           Studio solution file. Similarly the relative solution file path is
           placed as the values of the SccLocalPath[i] (where [i] ranges from
           0 to the number of projects in the solution) attributes of the
           GlobalSection(SourceCodeControl) section of the Microsoft Visual
           Studio solution file. This is used only if the MSVS_SCC_PROVIDER
           construction variable is also set. The default value is the current
           working directory.

       MSVS_SCC_PROJECT_NAME
           The project name placed in a generated Microsoft Visual Studio
           project file as the value of the SccProjectName attribute if the
           MSVS_SCC_PROVIDER construction variable is also set. In this case
           the string is also placed in the SccProjectName0 attribute of the
           GlobalSection(SourceCodeControl) section of the Microsoft Visual
           Studio solution file. There is no default value.

       MSVS_SCC_PROVIDER
           The string placed in a generated Microsoft Visual Studio project
           file as the value of the SccProvider attribute. The string is also
           placed in the SccProvider0 attribute of the
           GlobalSection(SourceCodeControl) section of the Microsoft Visual
           Studio solution file. There is no default value.

       MSVS_VERSION
           Sets the preferred version of Microsoft Visual Studio to use.

           If $MSVS_VERSION is not set, SCons will (by default) select the
           latest version of Visual Studio installed on your system. So, if
           you have version 6 and version 7 (MSVS .NET) installed, it will
           prefer version 7. You can override this by specifying the
           MSVS_VERSION variable in the Environment initialization, setting it
           to the appropriate version ('6.0' or '7.0', for example). If the
           specified version isn't installed, tool initialization will fail.

           This is obsolete: use $MSVC_VERSION instead. If $MSVS_VERSION is
           set and $MSVC_VERSION is not, $MSVC_VERSION will be set
           automatically to $MSVS_VERSION. If both are set to different
           values, scons will raise an error.

       MSVSBUILDCOM
           The build command line placed in a generated Microsoft Visual
           Studio project file. The default is to have Visual Studio invoke
           SCons with any specified build targets.

       MSVSCLEANCOM
           The clean command line placed in a generated Microsoft Visual
           Studio project file. The default is to have Visual Studio invoke
           SCons with the -c option to remove any specified targets.

       MSVSENCODING
           The encoding string placed in a generated Microsoft Visual Studio
           project file. The default is encoding Windows-1252.

       MSVSPROJECTCOM
           The action used to generate Microsoft Visual Studio project files.

       MSVSPROJECTSUFFIX
           The suffix used for Microsoft Visual Studio project (DSP) files.
           The default value is .vcproj when using Visual Studio version 7.x
           (.NET) or later version, and .dsp when using earlier versions of
           Visual Studio.

       MSVSREBUILDCOM
           The rebuild command line placed in a generated Microsoft Visual
           Studio project file. The default is to have Visual Studio invoke
           SCons with any specified rebuild targets.

       MSVSSCONS
           The SCons used in generated Microsoft Visual Studio project files.
           The default is the version of SCons being used to generate the
           project file.

       MSVSSCONSCOM
           The default SCons command used in generated Microsoft Visual Studio
           project files.

       MSVSSCONSCRIPT
           The sconscript file (that is, SConstruct or SConscript file) that
           will be invoked by Visual Studio project files (through the
           $MSVSSCONSCOM variable). The default is the same sconscript file
           that contains the call to MSVSProject to build the project file.

       MSVSSCONSFLAGS
           The SCons flags used in generated Microsoft Visual Studio project
           files.

       MSVSSOLUTIONCOM
           The action used to generate Microsoft Visual Studio solution files.

       MSVSSOLUTIONSUFFIX
           The suffix used for Microsoft Visual Studio solution (DSW) files.
           The default value is .sln when using Visual Studio version 7.x
           (.NET), and .dsw when using earlier versions of Visual Studio.

       MT
           The program used on Windows systems to embed manifests into DLLs
           and EXEs. See also $WINDOWS_EMBED_MANIFEST.

       MTEXECOM
           The Windows command line used to embed manifests into executables.
           See also $MTSHLIBCOM.

       MTFLAGS
           Flags passed to the $MT manifest embedding program (Windows only).

       MTSHLIBCOM
           The Windows command line used to embed manifests into shared
           libraries (DLLs). See also $MTEXECOM.

       MWCW_VERSION
           The version number of the MetroWerks CodeWarrior C compiler to be
           used.

       MWCW_VERSIONS
           A list of installed versions of the MetroWerks CodeWarrior C
           compiler on this system.

       NAME
           Specfies the name of the project to package.

           See the Package builder.

       NINJA_ALIAS_NAME
           Name of the Alias() which is will cause SCons to create the
           ninja.build file, and then (optionally) run ninja.

       NINJA_COMPDB_EXPAND
           Boolean value (True|False) to instruct ninja to expand the command
           line arguments normally put into response files. This prevents
           lines in the compilation database like "gcc @rsp_file" and instead
           yields "gcc -c -o myfile.o myfile.c -Ia -DXYZ"

           Ninja's compdb tool added the "-x" flag in Ninja V1.9.0

       NINJA_DIR
           This propagates directly into the generated ninja.build file. From
           Ninja's docs: builddir A directory for some Ninja output files. ...
           (You can also store other build output in this directory.)

       NINJA_DISABLE_AUTO_RUN
           Boolean (True|False). Default: False When True, SCons will not run
           ninja automatically after creating the ninja.build file. If not
           set, this will be set to True if "--disable_execute_ninja" or
           SetOption('disable_execute_ninja', True)

       NINJA_ENV_VAR_CACHE
           A string that sets the environment for any environment variables
           that differ between the OS environment and the SCons command ENV.
           It will be compatible with the default shell of the operating
           system. If not explicitly specified, SCons will generate this
           dynamically from the Environment()'s 'ENV' "env['ENV']" where those
           values differ from the existing shell..

       NINJA_FILE_NAME
           The filename for the generated Ninja build file defaults to
           ninja.build

       NINJA_GENERATED_SOURCE_SUFFIXES
           The list of source file suffixes which are generated by SCons build
           steps. All source files which match these suffixes will be added to
           the _generated_sources alias in the output ninja.build file. Then
           all other source files will be made to depend on this in the
           ninja.build file, forcing the generated sources to be built first.

       NINJA_MSVC_DEPS_PREFIX
           This propagates directly into the generated ninja.build file. From
           Ninja's docs "defines the string which should be stripped from
           msvc's /showIncludes output"

       NINJA_POOL
           Set the "ninja_pool" for this or all targets in scope for this env
           var.

       NINJA_REGENERATE_DEPS
           A generator function used to create a ninja depsfile which includes
           all the files which would require SCons to be invoked if they
           change. Or a list of said files.

       _NINJA_REGENERATE_DEPS_FUNC
           Internal value used to specify the function to call with argument
           env to generate the list of files which if changed would require
           the ninja file to be regenerated.

       NINJA_SYNTAX
           Theres also NINJA_SYNTAX which is the path to a custom
           ninja_syntax.py file which is used in generation. The tool
           currently assumes you have ninja installed through pip, and grabs
           the syntax file from that installation if none specified.

       no_import_lib
           When set to non-zero, suppresses creation of a corresponding
           Windows static import lib by the SharedLibrary builder when used
           with MinGW, Microsoft Visual Studio or Metrowerks. This also
           suppresses creation of an export (.exp) file when using Microsoft
           Visual Studio.

       OBJPREFIX
           The prefix used for (static) object file names.

       OBJSUFFIX
           The suffix used for (static) object file names.

       PACKAGEROOT
           Specifies the directory where all files in resulting archive will
           be placed if applicable. The default value is "$NAME-$VERSION".

           See the Package builder.

       PACKAGETYPE
           Selects the package type to build when using the Package builder.
           May be a string or list of strings. See the docuentation for the
           builder for the currently supported types.


           $PACKAGETYPE may be overridden with the --package-type command line
           option.

           See the Package builder.

       PACKAGEVERSION
           The version of the package (not the underlying project). This is
           currently only used by the rpm packager and should reflect changes
           in the packaging, not the underlying project code itself.

           See the Package builder.

       PCH
           The Microsoft Visual C++ precompiled header that will be used when
           compiling object files. This variable is ignored by tools other
           than Microsoft Visual C++. When this variable is defined SCons will
           add options to the compiler command line to cause it to use the
           precompiled header, and will also set up the dependencies for the
           PCH file. Example:

               env['PCH'] = 'StdAfx.pch'

       PCHCOM
           The command line used by the PCH builder to generated a precompiled
           header.

       PCHCOMSTR
           The string displayed when generating a precompiled header. If this
           is not set, then $PCHCOM (the command line) is displayed.

       PCHPDBFLAGS
           A construction variable that, when expanded, adds the /yD flag to
           the command line only if the $PDB construction variable is set.

       PCHSTOP
           This variable specifies how much of a source file is precompiled.
           This variable is ignored by tools other than Microsoft Visual C++,
           or when the PCH variable is not being used. When this variable is
           define it must be a string that is the name of the header that is
           included at the end of the precompiled portion of the source files,
           or the empty string if the "#pragma hrdstop" construct is being
           used:

               env['PCHSTOP'] = 'StdAfx.h'

       PDB
           The Microsoft Visual C++ PDB file that will store debugging
           information for object files, shared libraries, and programs. This
           variable is ignored by tools other than Microsoft Visual C++. When
           this variable is defined SCons will add options to the compiler and
           linker command line to cause them to generate external debugging
           information, and will also set up the dependencies for the PDB
           file. Example:

               env['PDB'] = 'hello.pdb'

           The Visual C++ compiler switch that SCons uses by default to
           generate PDB information is /Z7. This works correctly with parallel
           (-j) builds because it embeds the debug information in the
           intermediate object files, as opposed to sharing a single PDB file
           between multiple object files. This is also the only way to get
           debug information embedded into a static library. Using the /Zi
           instead may yield improved link-time performance, although parallel
           builds will no longer work. You can generate PDB files with the /Zi
           switch by overriding the default $CCPDBFLAGS variable; see the
           entry for that variable for specific examples.

       PDFLATEX
           The pdflatex utility.

       PDFLATEXCOM
           The command line used to call the pdflatex utility.

       PDFLATEXCOMSTR
           The string displayed when calling the pdflatex utility. If this is
           not set, then $PDFLATEXCOM (the command line) is displayed.

               env = Environment(PDFLATEX;COMSTR = "Building $TARGET from LaTeX input $SOURCES")

       PDFLATEXFLAGS
           General options passed to the pdflatex utility.

       PDFPREFIX
           The prefix used for PDF file names.

       PDFSUFFIX
           The suffix used for PDF file names.

       PDFTEX
           The pdftex utility.

       PDFTEXCOM
           The command line used to call the pdftex utility.

       PDFTEXCOMSTR
           The string displayed when calling the pdftex utility. If this is
           not set, then $PDFTEXCOM (the command line) is displayed.

               env = Environment(PDFTEXCOMSTR = "Building $TARGET from TeX input $SOURCES")

       PDFTEXFLAGS
           General options passed to the pdftex utility.

       PKGCHK
           On Solaris systems, the package-checking program that will be used
           (along with $PKGINFO) to look for installed versions of the Sun PRO
           C++ compiler. The default is /usr/sbin/pgkchk.

       PKGINFO
           On Solaris systems, the package information program that will be
           used (along with $PKGCHK) to look for installed versions of the Sun
           PRO C++ compiler. The default is pkginfo.

       PLATFORM
           The name of the platform used to create the Environment. If no
           platform is specified when the Environment is created, scons
           autodetects the platform.

               env = Environment(tools = [])
               if env['PLATFORM'] == 'cygwin':
                   Tool('mingw')(env)
               else:
                   Tool('msvc')(env)

       POAUTOINIT
           The $POAUTOINIT variable, if set to True (on non-zero numeric
           value), let the msginit tool to automatically initialize missing PO
           files with msginit(1). This applies to both, POInit and POUpdate
           builders (and others that use any of them).

       POCREATE_ALIAS
           Common alias for all PO files created with POInit builder (default:
           'po-create'). See msginit tool and POInit builder.

       POSUFFIX
           Suffix used for PO files (default: '.po') See msginit tool and
           POInit builder.

       POTDOMAIN
           The $POTDOMAIN defines default domain, used to generate POT
           filename as $POTDOMAIN.pot when no POT file name is provided by the
           user. This applies to POTUpdate, POInit and POUpdate builders (and
           builders, that use them, e.g.  Translate). Normally (if $POTDOMAIN
           is not defined), the builders use messages.pot as default POT file
           name.

       POTSUFFIX
           Suffix used for PO Template files (default: '.pot'). See xgettext
           tool and POTUpdate builder.

       POTUPDATE_ALIAS
           Name of the common phony target for all PO Templates created with
           POUpdate (default: 'pot-update'). See xgettext tool and POTUpdate
           builder.

       POUPDATE_ALIAS
           Common alias for all PO files being defined with POUpdate builder
           (default: 'po-update'). See msgmerge tool and POUpdate builder.

       PRINT_CMD_LINE_FUNC
           A Python function used to print the command lines as they are
           executed (assuming command printing is not disabled by the -q or -s
           options or their equivalents). The function should take four
           arguments: s, the command being executed (a string), target, the
           target being built (file node, list, or string name(s)), source,
           the source(s) used (file node, list, or string name(s)), and env,
           the environment being used.

           The function must do the printing itself. The default
           implementation, used if this variable is not set or is None, is:

               def print_cmd_line(s, target, source, env):
                 sys.stdout.write(s + "\n")

           Here's an example of a more interesting function:

               def print_cmd_line(s, target, source, env):
                  sys.stdout.write("Building %s -> %s...\n" %
                   (' and '.join([str(x) for x in source]),
                    ' and '.join([str(x) for x in target])))
               env=Environment(PRINT_CMD_LINE_FUNC=print_cmd_line)
               env.Program('foo', 'foo.c')

           This just prints "Building targetname from sourcename..." instead
           of the actual commands. Such a function could also log the actual
           commands to a log file, for example.

       PROGEMITTER
           Contains the emitter specification for the Program builder. The
           manpage section "Builder Objects" contains general information on
           specifying emitters.

       PROGPREFIX
           The prefix used for executable file names.

       PROGSUFFIX
           The suffix used for executable file names.

       PSCOM
           The command line used to convert TeX DVI files into a PostScript
           file.

       PSCOMSTR
           The string displayed when a TeX DVI file is converted into a
           PostScript file. If this is not set, then $PSCOM (the command line)
           is displayed.

       PSPREFIX
           The prefix used for PostScript file names.

       PSSUFFIX
           The prefix used for PostScript file names.

       QT_AUTOSCAN
           Turn off scanning for mocable files. Use the Moc Builder to
           explicitly specify files to run moc on.

       QT_BINPATH
           The path where the qt binaries are installed. The default value is
           '$QTDIR/bin'.

       QT_CPPPATH
           The path where the qt header files are installed. The default value
           is '$QTDIR/include'. Note: If you set this variable to None, the
           tool won't change the $CPPPATH construction variable.

       QT_DEBUG
           Prints lots of debugging information while scanning for moc files.

       QT_LIB
           Default value is 'qt'. You may want to set this to 'qt-mt'. Note:
           If you set this variable to None, the tool won't change the $LIBS
           variable.

       QT_LIBPATH
           The path where the qt libraries are installed. The default value is
           '$QTDIR/lib'. Note: If you set this variable to None, the tool
           won't change the $LIBPATH construction variable.

       QT_MOC
           Default value is '$QT_BINPATH/moc'.

       QT_MOCCXXPREFIX
           Default value is ''. Prefix for moc output files, when source is a
           cxx file.

       QT_MOCCXXSUFFIX
           Default value is '.moc'. Suffix for moc output files, when source
           is a cxx file.

       QT_MOCFROMCXXCOM
           Command to generate a moc file from a cpp file.

       QT_MOCFROMCXXCOMSTR
           The string displayed when generating a moc file from a cpp file. If
           this is not set, then $QT_MOCFROMCXXCOM (the command line) is
           displayed.

       QT_MOCFROMCXXFLAGS
           Default value is '-i'. These flags are passed to moc, when moccing
           a C++ file.

       QT_MOCFROMHCOM
           Command to generate a moc file from a header.

       QT_MOCFROMHCOMSTR
           The string displayed when generating a moc file from a cpp file. If
           this is not set, then $QT_MOCFROMHCOM (the command line) is
           displayed.

       QT_MOCFROMHFLAGS
           Default value is ''. These flags are passed to moc, when moccing a
           header file.

       QT_MOCHPREFIX
           Default value is 'moc_'. Prefix for moc output files, when source
           is a header.

       QT_MOCHSUFFIX
           Default value is '$CXXFILESUFFIX'. Suffix for moc output files,
           when source is a header.

       QT_UIC
           Default value is '$QT_BINPATH/uic'.

       QT_UICCOM
           Command to generate header files from .ui files.

       QT_UICCOMSTR
           The string displayed when generating header files from .ui files.
           If this is not set, then $QT_UICCOM (the command line) is
           displayed.

       QT_UICDECLFLAGS
           Default value is ''. These flags are passed to uic, when creating a
           a h file from a .ui file.

       QT_UICDECLPREFIX
           Default value is ''. Prefix for uic generated header files.

       QT_UICDECLSUFFIX
           Default value is '.h'. Suffix for uic generated header files.

       QT_UICIMPLFLAGS
           Default value is ''. These flags are passed to uic, when creating a
           cxx file from a .ui file.

       QT_UICIMPLPREFIX
           Default value is 'uic_'. Prefix for uic generated implementation
           files.

       QT_UICIMPLSUFFIX
           Default value is '$CXXFILESUFFIX'. Suffix for uic generated
           implementation files.

       QT_UISUFFIX
           Default value is '.ui'. Suffix of designer input files.

       QTDIR
           The qt tool tries to take this from os.environ. It also initializes
           all QT_* construction variables listed below. (Note that all paths
           are constructed with python's os.path.join() method, but are listed
           here with the '/' separator for easier reading.) In addition, the
           construction environment variables $CPPPATH, $LIBPATH and $LIBS may
           be modified and the variables $PROGEMITTER, $SHLIBEMITTER and
           $LIBEMITTER are modified. Because the build-performance is affected
           when using this tool, you have to explicitly specify it at
           Environment creation:

               Environment(tools=['default','qt'])

           The qt tool supports the following operations:


           Automatic moc file generation from header files.  You do not have
           to specify moc files explicitly, the tool does it for you. However,
           there are a few preconditions to do so: Your header file must have
           the same filebase as your implementation file and must stay in the
           same directory. It must have one of the suffixes .h, .hpp, .H,
           .hxx, .hh. You can turn off automatic moc file generation by
           setting QT_AUTOSCAN to 0. See also the corresponding Moc() builder
           method.


           Automatic moc file generation from cxx files.  As stated in the qt
           documentation, include the moc file at the end of the cxx file.
           Note that you have to include the file, which is generated by the
           transformation ${QT_MOCCXXPREFIX}<basename>${QT_MOCCXXSUFFIX}, by
           default <basename>.moc. A warning is generated after building the
           moc file, if you do not include the correct file. If you are using
           VariantDir, you may need to specify duplicate=1. You can turn off
           automatic moc file generation by setting QT_AUTOSCAN to 0. See also
           the corresponding Moc builder method.


           Automatic handling of .ui files.  The implementation files
           generated from .ui files are handled much the same as yacc or lex
           files. Each .ui file given as a source of Program, Library or
           SharedLibrary will generate three files, the declaration file, the
           implementation file and a moc file. Because there are also
           generated headers, you may need to specify duplicate=1 in calls to
           VariantDir. See also the corresponding Uic builder method.

       RANLIB
           The archive indexer.

       RANLIBCOM
           The command line used to index a static library archive.

       RANLIBCOMSTR
           The string displayed when a static library archive is indexed. If
           this is not set, then $RANLIBCOM (the command line) is displayed.

               env = Environment(RANLIBCOMSTR = "Indexing $TARGET")

       RANLIBFLAGS
           General options passed to the archive indexer.

       RC
           The resource compiler used to build a Microsoft Visual C++ resource
           file.

       RCCOM
           The command line used to build a Microsoft Visual C++ resource
           file.

       RCCOMSTR
           The string displayed when invoking the resource compiler to build a
           Microsoft Visual C++ resource file. If this is not set, then $RCCOM
           (the command line) is displayed.

       RCFLAGS
           The flags passed to the resource compiler by the RES builder.

       RCINCFLAGS
           An automatically-generated construction variable containing the
           command-line options for specifying directories to be searched by
           the resource compiler. The value of $RCINCFLAGS is created by
           respectively prepending and appending $RCINCPREFIX and $RCINCSUFFIX
           to the beginning and end of each directory in $CPPPATH.

       RCINCPREFIX
           The prefix (flag) used to specify an include directory on the
           resource compiler command line. This will be prepended to the
           beginning of each directory in the $CPPPATH construction variable
           when the $RCINCFLAGS variable is expanded.

       RCINCSUFFIX
           The suffix used to specify an include directory on the resource
           compiler command line. This will be appended to the end of each
           directory in the $CPPPATH construction variable when the
           $RCINCFLAGS variable is expanded.

       RDirs
           A function that converts a string into a list of Dir instances by
           searching the repositories.

       REGSVR
           The program used on Windows systems to register a newly-built DLL
           library whenever the SharedLibrary builder is passed a keyword
           argument of register=True.

       REGSVRCOM
           The command line used on Windows systems to register a newly-built
           DLL library whenever the SharedLibrary builder is passed a keyword
           argument of register=True.

       REGSVRCOMSTR
           The string displayed when registering a newly-built DLL file. If
           this is not set, then $REGSVRCOM (the command line) is displayed.

       REGSVRFLAGS
           Flags passed to the DLL registration program on Windows systems
           when a newly-built DLL library is registered. By default, this
           includes the /s that prevents dialog boxes from popping up and
           requiring user attention.

       RMIC
           The Java RMI stub compiler.

       RMICCOM
           The command line used to compile stub and skeleton class files from
           Java classes that contain RMI implementations. Any options
           specified in the $RMICFLAGS construction variable are included on
           this command line.

       RMICCOMSTR
           The string displayed when compiling stub and skeleton class files
           from Java classes that contain RMI implementations. If this is not
           set, then $RMICCOM (the command line) is displayed.

               env = Environment(RMICCOMSTR = "Generating stub/skeleton class files $TARGETS from $SOURCES")

       RMICFLAGS
           General options passed to the Java RMI stub compiler.

       RPATH
           A list of paths to search for shared libraries when running
           programs. Currently only used in the GNU (gnulink), IRIX (sgilink)
           and Sun (sunlink) linkers. Ignored on platforms and toolchains that
           don't support it. Note that the paths added to RPATH are not
           transformed by scons in any way: if you want an absolute path, you
           must make it absolute yourself.

       _RPATH
           An automatically-generated construction variable containing the
           rpath flags to be used when linking a program with shared
           libraries. The value of $_RPATH is created by respectively
           prepending $RPATHPREFIX and appending $RPATHSUFFIX to the beginning
           and end of each directory in $RPATH.

       RPATHPREFIX
           The prefix used to specify a directory to be searched for shared
           libraries when running programs. This will be prepended to the
           beginning of each directory in the $RPATH construction variable
           when the $_RPATH variable is automatically generated.

       RPATHSUFFIX
           The suffix used to specify a directory to be searched for shared
           libraries when running programs. This will be appended to the end
           of each directory in the $RPATH construction variable when the
           $_RPATH variable is automatically generated.

       RPCGEN
           The RPC protocol compiler.

       RPCGENCLIENTFLAGS
           Options passed to the RPC protocol compiler when generating client
           side stubs. These are in addition to any flags specified in the
           $RPCGENFLAGS construction variable.

       RPCGENFLAGS
           General options passed to the RPC protocol compiler.

       RPCGENHEADERFLAGS
           Options passed to the RPC protocol compiler when generating a
           header file. These are in addition to any flags specified in the
           $RPCGENFLAGS construction variable.

       RPCGENSERVICEFLAGS
           Options passed to the RPC protocol compiler when generating server
           side stubs. These are in addition to any flags specified in the
           $RPCGENFLAGS construction variable.

       RPCGENXDRFLAGS
           Options passed to the RPC protocol compiler when generating XDR
           routines. These are in addition to any flags specified in the
           $RPCGENFLAGS construction variable.

       SCANNERS
           A list of the available implicit dependency scanners. New file
           scanners may be added by appending to this list, although the more
           flexible approach is to associate scanners with a specific Builder.
           See the manpage sections "Builder Objects" and "Scanner Objects"
           for more information.

       SCONS_HOME
           The (optional) path to the SCons library directory, initialized
           from the external environment. If set, this is used to construct a
           shorter and more efficient search path in the $MSVSSCONS command
           line executed from Microsoft Visual Studio project files.

       SHCC
           The C compiler used for generating shared-library objects. See also
           $CC for compiling to static objects.

       SHCCCOM
           The command line used to compile a C source file to a
           shared-library object file. Any options specified in the $SHCFLAGS,
           $SHCCFLAGS and $CPPFLAGS construction variables are included on
           this command line. See also $CCCOM for compiling to static objects.

       SHCCCOMSTR
           If set, the string displayed when a C source file is compiled to a
           shared object file. If not set, then $SHCCCOM (the command line) is
           displayed. See also $CCCOMSTR for compiling to static objects.

               env = Environment(SHCCCOMSTR = "Compiling shared object $TARGET")

       SHCCFLAGS
           Options that are passed to the C and C++ compilers to generate
           shared-library objects. See also $CCFLAGS for compiling to static
           objects.

       SHCFLAGS
           Options that are passed to the C compiler (only; not C++) to
           generate shared-library objects. See also $CFLAGS for compiling to
           static objects.

       SHCXX
           The C++ compiler used for generating shared-library objects. See
           also $CXX for compiling to static objects.

       SHCXXCOM
           The command line used to compile a C++ source file to a
           shared-library object file. Any options specified in the
           $SHCXXFLAGS and $CPPFLAGS construction variables are included on
           this command line. See also $CXXCOM for compiling to static
           objects.

       SHCXXCOMSTR
           If set, the string displayed when a C++ source file is compiled to
           a shared object file. If not set, then $SHCXXCOM (the command line)
           is displayed. See also $CXXCOMSTR for compiling to static objects.

               env = Environment(SHCXXCOMSTR = "Compiling shared object $TARGET")

       SHCXXFLAGS
           Options that are passed to the C++ compiler to generate
           shared-library objects. See also $CXXFLAGS for compiling to static
           objects.

       SHDC
           The name of the compiler to use when compiling D source destined to
           be in a shared objects. See also $DC for compiling to static
           objects.

       SHDCOM
           The command line to use when compiling code to be part of shared
           objects. See also $DCOM for compiling to static objects.

       SHDCOMSTR
           If set, the string displayed when a D source file is compiled to a
           (shared) object file. If not set, then $SHDCOM (the command line)
           is displayed. See also $DCOMSTR for compiling to static objects.

       SHDLIBVERSIONFLAGS
           Extra flags added to $SHDLINKCOM when building versioned
           SharedLibrary. These flags are only used when $SHLIBVERSION is set.

       SHDLINK
           The linker to use when creating shared objects for code bases
           include D sources. See also $DLINK for linking static objects.

       SHDLINKCOM
           The command line to use when generating shared objects. See also
           $DLINKCOM for linking static objects.

       SHDLINKFLAGS
           The list of flags to use when generating a shared object. See also
           $DLINKFLAGS for linking static objects.

       SHELL
           A string naming the shell program that will be passed to the $SPAWN
           function. See the $SPAWN construction variable for more
           information.

       SHF03
           The Fortran 03 compiler used for generating shared-library objects.
           You should normally set the $SHFORTRAN variable, which specifies
           the default Fortran compiler for all Fortran versions. You only
           need to set $SHF03 if you need to use a specific compiler or
           compiler version for Fortran 03 files.

       SHF03COM
           The command line used to compile a Fortran 03 source file to a
           shared-library object file. You only need to set $SHF03COM if you
           need to use a specific command line for Fortran 03 files. You
           should normally set the $SHFORTRANCOM variable, which specifies the
           default command line for all Fortran versions.

       SHF03COMSTR
           If set, the string displayed when a Fortran 03 source file is
           compiled to a shared-library object file. If not set, then
           $SHF03COM or $SHFORTRANCOM (the command line) is displayed.

       SHF03FLAGS
           Options that are passed to the Fortran 03 compiler to generated
           shared-library objects. You only need to set $SHF03FLAGS if you
           need to define specific user options for Fortran 03 files. You
           should normally set the $SHFORTRANFLAGS variable, which specifies
           the user-specified options passed to the default Fortran compiler
           for all Fortran versions.

       SHF03PPCOM
           The command line used to compile a Fortran 03 source file to a
           shared-library object file after first running the file through the
           C preprocessor. Any options specified in the $SHF03FLAGS and
           $CPPFLAGS construction variables are included on this command line.
           You only need to set $SHF03PPCOM if you need to use a specific
           C-preprocessor command line for Fortran 03 files. You should
           normally set the $SHFORTRANPPCOM variable, which specifies the
           default C-preprocessor command line for all Fortran versions.

       SHF03PPCOMSTR
           If set, the string displayed when a Fortran 03 source file is
           compiled to a shared-library object file after first running the
           file through the C preprocessor. If not set, then $SHF03PPCOM or
           $SHFORTRANPPCOM (the command line) is displayed.

       SHF08
           The Fortran 08 compiler used for generating shared-library objects.
           You should normally set the $SHFORTRAN variable, which specifies
           the default Fortran compiler for all Fortran versions. You only
           need to set $SHF08 if you need to use a specific compiler or
           compiler version for Fortran 08 files.

       SHF08COM
           The command line used to compile a Fortran 08 source file to a
           shared-library object file. You only need to set $SHF08COM if you
           need to use a specific command line for Fortran 08 files. You
           should normally set the $SHFORTRANCOM variable, which specifies the
           default command line for all Fortran versions.

       SHF08COMSTR
           If set, the string displayed when a Fortran 08 source file is
           compiled to a shared-library object file. If not set, then
           $SHF08COM or $SHFORTRANCOM (the command line) is displayed.

       SHF08FLAGS
           Options that are passed to the Fortran 08 compiler to generated
           shared-library objects. You only need to set $SHF08FLAGS if you
           need to define specific user options for Fortran 08 files. You
           should normally set the $SHFORTRANFLAGS variable, which specifies
           the user-specified options passed to the default Fortran compiler
           for all Fortran versions.

       SHF08PPCOM
           The command line used to compile a Fortran 08 source file to a
           shared-library object file after first running the file through the
           C preprocessor. Any options specified in the $SHF08FLAGS and
           $CPPFLAGS construction variables are included on this command line.
           You only need to set $SHF08PPCOM if you need to use a specific
           C-preprocessor command line for Fortran 08 files. You should
           normally set the $SHFORTRANPPCOM variable, which specifies the
           default C-preprocessor command line for all Fortran versions.

       SHF08PPCOMSTR
           If set, the string displayed when a Fortran 08 source file is
           compiled to a shared-library object file after first running the
           file through the C preprocessor. If not set, then $SHF08PPCOM or
           $SHFORTRANPPCOM (the command line) is displayed.

       SHF77
           The Fortran 77 compiler used for generating shared-library objects.
           You should normally set the $SHFORTRAN variable, which specifies
           the default Fortran compiler for all Fortran versions. You only
           need to set $SHF77 if you need to use a specific compiler or
           compiler version for Fortran 77 files.

       SHF77COM
           The command line used to compile a Fortran 77 source file to a
           shared-library object file. You only need to set $SHF77COM if you
           need to use a specific command line for Fortran 77 files. You
           should normally set the $SHFORTRANCOM variable, which specifies the
           default command line for all Fortran versions.

       SHF77COMSTR
           If set, the string displayed when a Fortran 77 source file is
           compiled to a shared-library object file. If not set, then
           $SHF77COM or $SHFORTRANCOM (the command line) is displayed.

       SHF77FLAGS
           Options that are passed to the Fortran 77 compiler to generated
           shared-library objects. You only need to set $SHF77FLAGS if you
           need to define specific user options for Fortran 77 files. You
           should normally set the $SHFORTRANFLAGS variable, which specifies
           the user-specified options passed to the default Fortran compiler
           for all Fortran versions.

       SHF77PPCOM
           The command line used to compile a Fortran 77 source file to a
           shared-library object file after first running the file through the
           C preprocessor. Any options specified in the $SHF77FLAGS and
           $CPPFLAGS construction variables are included on this command line.
           You only need to set $SHF77PPCOM if you need to use a specific
           C-preprocessor command line for Fortran 77 files. You should
           normally set the $SHFORTRANPPCOM variable, which specifies the
           default C-preprocessor command line for all Fortran versions.

       SHF77PPCOMSTR
           If set, the string displayed when a Fortran 77 source file is
           compiled to a shared-library object file after first running the
           file through the C preprocessor. If not set, then $SHF77PPCOM or
           $SHFORTRANPPCOM (the command line) is displayed.

       SHF90
           The Fortran 90 compiler used for generating shared-library objects.
           You should normally set the $SHFORTRAN variable, which specifies
           the default Fortran compiler for all Fortran versions. You only
           need to set $SHF90 if you need to use a specific compiler or
           compiler version for Fortran 90 files.

       SHF90COM
           The command line used to compile a Fortran 90 source file to a
           shared-library object file. You only need to set $SHF90COM if you
           need to use a specific command line for Fortran 90 files. You
           should normally set the $SHFORTRANCOM variable, which specifies the
           default command line for all Fortran versions.

       SHF90COMSTR
           If set, the string displayed when a Fortran 90 source file is
           compiled to a shared-library object file. If not set, then
           $SHF90COM or $SHFORTRANCOM (the command line) is displayed.

       SHF90FLAGS
           Options that are passed to the Fortran 90 compiler to generated
           shared-library objects. You only need to set $SHF90FLAGS if you
           need to define specific user options for Fortran 90 files. You
           should normally set the $SHFORTRANFLAGS variable, which specifies
           the user-specified options passed to the default Fortran compiler
           for all Fortran versions.

       SHF90PPCOM
           The command line used to compile a Fortran 90 source file to a
           shared-library object file after first running the file through the
           C preprocessor. Any options specified in the $SHF90FLAGS and
           $CPPFLAGS construction variables are included on this command line.
           You only need to set $SHF90PPCOM if you need to use a specific
           C-preprocessor command line for Fortran 90 files. You should
           normally set the $SHFORTRANPPCOM variable, which specifies the
           default C-preprocessor command line for all Fortran versions.

       SHF90PPCOMSTR
           If set, the string displayed when a Fortran 90 source file is
           compiled to a shared-library object file after first running the
           file through the C preprocessor. If not set, then $SHF90PPCOM or
           $SHFORTRANPPCOM (the command line) is displayed.

       SHF95
           The Fortran 95 compiler used for generating shared-library objects.
           You should normally set the $SHFORTRAN variable, which specifies
           the default Fortran compiler for all Fortran versions. You only
           need to set $SHF95 if you need to use a specific compiler or
           compiler version for Fortran 95 files.

       SHF95COM
           The command line used to compile a Fortran 95 source file to a
           shared-library object file. You only need to set $SHF95COM if you
           need to use a specific command line for Fortran 95 files. You
           should normally set the $SHFORTRANCOM variable, which specifies the
           default command line for all Fortran versions.

       SHF95COMSTR
           If set, the string displayed when a Fortran 95 source file is
           compiled to a shared-library object file. If not set, then
           $SHF95COM or $SHFORTRANCOM (the command line) is displayed.

       SHF95FLAGS
           Options that are passed to the Fortran 95 compiler to generated
           shared-library objects. You only need to set $SHF95FLAGS if you
           need to define specific user options for Fortran 95 files. You
           should normally set the $SHFORTRANFLAGS variable, which specifies
           the user-specified options passed to the default Fortran compiler
           for all Fortran versions.

       SHF95PPCOM
           The command line used to compile a Fortran 95 source file to a
           shared-library object file after first running the file through the
           C preprocessor. Any options specified in the $SHF95FLAGS and
           $CPPFLAGS construction variables are included on this command line.
           You only need to set $SHF95PPCOM if you need to use a specific
           C-preprocessor command line for Fortran 95 files. You should
           normally set the $SHFORTRANPPCOM variable, which specifies the
           default C-preprocessor command line for all Fortran versions.

       SHF95PPCOMSTR
           If set, the string displayed when a Fortran 95 source file is
           compiled to a shared-library object file after first running the
           file through the C preprocessor. If not set, then $SHF95PPCOM or
           $SHFORTRANPPCOM (the command line) is displayed.

       SHFORTRAN
           The default Fortran compiler used for generating shared-library
           objects.

       SHFORTRANCOM
           The command line used to compile a Fortran source file to a
           shared-library object file.

       SHFORTRANCOMSTR
           If set, the string displayed when a Fortran source file is compiled
           to a shared-library object file. If not set, then $SHFORTRANCOM
           (the command line) is displayed.

       SHFORTRANFLAGS
           Options that are passed to the Fortran compiler to generate
           shared-library objects.

       SHFORTRANPPCOM
           The command line used to compile a Fortran source file to a
           shared-library object file after first running the file through the
           C preprocessor. Any options specified in the $SHFORTRANFLAGS and
           $CPPFLAGS construction variables are included on this command line.

       SHFORTRANPPCOMSTR
           If set, the string displayed when a Fortran source file is compiled
           to a shared-library object file after first running the file
           through the C preprocessor. If not set, then $SHFORTRANPPCOM (the
           command line) is displayed.

       SHLIBEMITTER
           Contains the emitter specification for the SharedLibrary builder.
           The manpage section "Builder Objects" contains general information
           on specifying emitters.

       SHLIBNOVERSIONSYMLINKS
           Instructs the SharedLibrary builder to not create symlinks for
           versioned shared libraries.

       SHLIBPREFIX
           The prefix used for shared library file names.

       _SHLIBSONAME
           A macro that automatically generates shared library's SONAME based
           on $TARGET, $SHLIBVERSION and $SHLIBSUFFIX. Used by SharedLibrary
           builder when the linker tool supports SONAME (e.g.  gnulink).

       SHLIBSUFFIX
           The suffix used for shared library file names.

       SHLIBVERSION
           When this construction variable is defined, a versioned shared
           library is created by the SharedLibrary builder. This activates the
           $_SHLIBVERSIONFLAGS and thus modifies the $SHLINKCOM as required,
           adds the version number to the library name, and creates the
           symlinks that are needed.  $SHLIBVERSION versions should exist as
           alpha-numeric, decimal-delimited values as defined by the regular
           expression "\w+[\.\w+]*". Example $SHLIBVERSION values include '1',
           '1.2.3', and '1.2.gitaa412c8b'.

       _SHLIBVERSIONFLAGS
           This macro automatically introduces extra flags to $SHLINKCOM when
           building versioned SharedLibrary (that is when $SHLIBVERSION is
           set).  _SHLIBVERSIONFLAGS usually adds $SHLIBVERSIONFLAGS and some
           extra dynamically generated options (such as
           -Wl,-soname=$_SHLIBSONAME. It is unused by "plain" (unversioned)
           shared libraries.

       SHLIBVERSIONFLAGS
           Extra flags added to $SHLINKCOM when building versioned
           SharedLibrary. These flags are only used when $SHLIBVERSION is set.

       SHLINK
           The linker for programs that use shared libraries. See also $LINK
           for linking static objects.

           On POSIX systems (those using the link tool), you should normally
           not change this value as it defaults to a "smart" linker tool which
           selects a compiler driver matching the type of source files in use.
           So for example, if you set $SHCXX to a specific compiler name, and
           are compiling C++ sources, the smartlink function will
           automatically select the same compiler for linking.

       SHLINKCOM
           The command line used to link programs using shared libraries. See
           also $LINKCOM for linking static objects.

       SHLINKCOMSTR
           The string displayed when programs using shared libraries are
           linked. If this is not set, then $SHLINKCOM (the command line) is
           displayed. See also $LINKCOMSTR for linking static objects.

               env = Environment(SHLINKCOMSTR = "Linking shared $TARGET")

       SHLINKFLAGS
           General user options passed to the linker for programs using shared
           libraries. Note that this variable should not contain -l (or
           similar) options for linking with the libraries listed in $LIBS,
           nor -L (or similar) include search path options that scons
           generates automatically from $LIBPATH. See $_LIBFLAGS above, for
           the variable that expands to library-link options, and
           $_LIBDIRFLAGS above, for the variable that expands to library
           search path options. See also $LINKFLAGS for linking static
           objects.

       SHOBJPREFIX
           The prefix used for shared object file names.

       SHOBJSUFFIX
           The suffix used for shared object file names.

       SONAME
           Variable used to hard-code SONAME for versioned shared
           library/loadable module.

               env.SharedLibrary('test', 'test.c', SHLIBVERSION='0.1.2', SONAME='libtest.so.2')

           The variable is used, for example, by gnulink linker tool.

       SOURCE
           A reserved variable name that may not be set or used in a
           construction environment. (See the manpage section "Variable
           Substitution" for more information).

       SOURCE_URL
           The URL (web address) of the location from which the project was
           retrieved. This is used to fill in the Source: field in the
           controlling information for Ipkg and RPM packages.

           See the Package builder.

       SOURCES
           A reserved variable name that may not be set or used in a
           construction environment. (See the manpage section "Variable
           Substitution" for more information).

       SOVERSION
           This will construct the SONAME using on the base library name (test
           in the example below) and use specified SOVERSION to create SONAME.

               env.SharedLibrary('test', 'test.c', SHLIBVERSION='0.1.2', SOVERSION='2')

           The variable is used, for example, by gnulink linker tool.

           In the example above SONAME would be libtest.so.2 which would be a
           symlink and point to libtest.so.0.1.2

       SPAWN
           A command interpreter function that will be called to execute
           command line strings. The function must expect the following
           arguments:

               def spawn(shell, escape, cmd, args, env):


           sh is a string naming the shell program to use.  escape is a
           function that can be called to escape shell special characters in
           the command line.  cmd is the path to the command to be executed.
           args is the arguments to the command.  env is a dictionary of the
           environment variables in which the command should be executed.

       STATIC_AND_SHARED_OBJECTS_ARE_THE_SAME
           When this variable is true, static objects and shared objects are
           assumed to be the same; that is, SCons does not check for linking
           static objects into a shared library.

       SUBST_DICT
           The dictionary used by the Substfile or Textfile builders for
           substitution values. It can be anything acceptable to the dict()
           constructor, so in addition to a dictionary, lists of tuples are
           also acceptable.

       SUBSTFILEPREFIX
           The prefix used for Substfile file names, an empty string by
           default.

       SUBSTFILESUFFIX
           The suffix used for Substfile file names, an empty string by
           default.

       SUMMARY
           A short summary of what the project is about. This is used to fill
           in the Summary: field in the controlling information for Ipkg and
           RPM packages, and as the Description: field in MSI packages.

           See the Package builder.

       SWIG
           The scripting language wrapper and interface generator.

       SWIGCFILESUFFIX
           The suffix that will be used for intermediate C source files
           generated by the scripting language wrapper and interface
           generator. The default value is _wrap$CFILESUFFIX. By default, this
           value is used whenever the -c++ option is not specified as part of
           the $SWIGFLAGS construction variable.

       SWIGCOM
           The command line used to call the scripting language wrapper and
           interface generator.

       SWIGCOMSTR
           The string displayed when calling the scripting language wrapper
           and interface generator. If this is not set, then $SWIGCOM (the
           command line) is displayed.

       SWIGCXXFILESUFFIX
           The suffix that will be used for intermediate C++ source files
           generated by the scripting language wrapper and interface
           generator. The default value is _wrap$CFILESUFFIX. By default, this
           value is used whenever the -c++ option is specified as part of the
           $SWIGFLAGS construction variable.

       SWIGDIRECTORSUFFIX
           The suffix that will be used for intermediate C++ header files
           generated by the scripting language wrapper and interface
           generator. These are only generated for C++ code when the SWIG
           'directors' feature is turned on. The default value is _wrap.h.

       SWIGFLAGS
           General options passed to the scripting language wrapper and
           interface generator. This is where you should set -python, -perl5,
           -tcl, or whatever other options you want to specify to SWIG. If you
           set the -c++ option in this variable, scons will, by default,
           generate a C++ intermediate source file with the extension that is
           specified as the $CXXFILESUFFIX variable.

       _SWIGINCFLAGS
           An automatically-generated construction variable containing the
           SWIG command-line options for specifying directories to be searched
           for included files. The value of $_SWIGINCFLAGS is created by
           respectively prepending and appending $SWIGINCPREFIX and
           $SWIGINCSUFFIX to the beginning and end of each directory in
           $SWIGPATH.

       SWIGINCPREFIX
           The prefix used to specify an include directory on the SWIG command
           line. This will be prepended to the beginning of each directory in
           the $SWIGPATH construction variable when the $_SWIGINCFLAGS
           variable is automatically generated.

       SWIGINCSUFFIX
           The suffix used to specify an include directory on the SWIG command
           line. This will be appended to the end of each directory in the
           $SWIGPATH construction variable when the $_SWIGINCFLAGS variable is
           automatically generated.

       SWIGOUTDIR
           Specifies the output directory in which the scripting language
           wrapper and interface generator should place generated
           language-specific files. This will be used by SCons to identify the
           files that will be generated by the swig call, and translated into
           the swig -outdir option on the command line.

       SWIGPATH
           The list of directories that the scripting language wrapper and
           interface generate will search for included files. The SWIG
           implicit dependency scanner will search these directories for
           include files. The default value is an empty list.

           Don't explicitly put include directory arguments in SWIGFLAGS; the
           result will be non-portable and the directories will not be
           searched by the dependency scanner. Note: directory names in
           SWIGPATH will be looked-up relative to the SConscript directory
           when they are used in a command. To force scons to look-up a
           directory relative to the root of the source tree use #:

               env = Environment(SWIGPATH='#/include')

           The directory look-up can also be forced using the Dir() function:

               include = Dir('include')
               env = Environment(SWIGPATH=include)

           The directory list will be added to command lines through the
           automatically-generated $_SWIGINCFLAGS construction variable, which
           is constructed by respectively prepending and appending the values
           of the $SWIGINCPREFIX and $SWIGINCSUFFIX construction variables to
           the beginning and end of each directory in $SWIGPATH. Any command
           lines you define that need the SWIGPATH directory list should
           include $_SWIGINCFLAGS:

               env = Environment(SWIGCOM="my_swig -o $TARGET $_SWIGINCFLAGS $SOURCES")

       SWIGVERSION
           The version number of the SWIG tool.

       TAR
           The tar archiver.

       TARCOM
           The command line used to call the tar archiver.

       TARCOMSTR
           The string displayed when archiving files using the tar archiver.
           If this is not set, then $TARCOM (the command line) is displayed.

               env = Environment(TARCOMSTR = "Archiving $TARGET")

       TARFLAGS
           General options passed to the tar archiver.

       TARGET
           A reserved variable name that may not be set or used in a
           construction environment. (See the manpage section "Variable
           Substitution" for more information).

       TARGET_ARCH
           The name of the target hardware architecture for the compiled
           objects created by this Environment. This defaults to the value of
           HOST_ARCH, and the user can override it. Currently only set for
           Win32.

           Sets the target architecture for the Visual C++ compiler (i.e. the
           arch of the binaries generated by the compiler). If not set,
           default to $HOST_ARCH, or, if that is unset, to the architecture of
           the running machine's OS (note that the python build or
           architecture has no effect). This variable must be passed as an
           argument to the Environment() constructor; setting it later has no
           effect. This is currently only used on Windows, but in the future
           it will be used on other OSes as well. If this is set and
           $MSVC_VERSION is not set, this will search for all installed MSVC's
           that support the $TARGET_ARCH, selecting the latest version for
           use.

           On Windows, valid target values are x86, arm, i386 for 32-bit
           targets and amd64, arm64, em64t, x86_64 and ia64 (Itanium) for
           64-bit targets. Note that not all target architectures are
           supported for all Visual Studio / MSVC versions. Check the relevant
           Microsoft documentation.

           For example, if you want to compile 64-bit binaries, you would set
           TARGET_ARCH='x86_64' in your SCons environment.

       TARGET_OS
           The name of the target operating system for the compiled objects
           created by this Environment. This defaults to the value of HOST_OS,
           and the user can override it. Currently only set for Win32.

       TARGETS
           A reserved variable name that may not be set or used in a
           construction environment. (See the manpage section "Variable
           Substitution" for more information).

       TARSUFFIX
           The suffix used for tar file names.

       TEMPFILEARGESCFUNC
           A default argument escape function is ``SCons.Subst.quote_spaces``.
           If you need to apply extra operations on a command argument before
           writing to a temporary file(fix Windows slashes, normalize paths,
           etc.), please set `TEMPFILEARGESCFUNC` variable to a custom
           function. Example::

               import sys
               import re
               from SCons.Subst import quote_spaces

               WINPATHSEP_RE = re.compile(r"\\([^\"'\\]|$)")

               def tempfile_arg_esc_func(arg):
                   arg = quote_spaces(arg)
                   if sys.platform != "win32":
                       return arg
                   # GCC requires double Windows slashes, let's use UNIX separator
                   return WINPATHSEP_RE.sub(r"/\1", arg)

               env["TEMPFILEARGESCFUNC"] = tempfile_arg_esc_func

       TEMPFILEARGJOIN
           The string (or character) to be used to join the arguments passed
           to TEMPFILE when command line exceeds the limit set by
           $MAXLINELENGTH. The default value is a space. However for MSVC,
           MSLINK the default is a line seperator characters as defined by
           os.linesep. Note this value is used literally and not expanded by
           the subst logic.

       TEMPFILEDIR
           The directory to create the tempfile in.

       TEMPFILEPREFIX
           The prefix for a temporary file used to store lines lines longer
           than $MAXLINELENGTH as operations which call out to a shell will
           fail if the line is too long, which particularly impacts linking.
           The default is '@', which works for the Microsoft and GNU
           toolchains on Windows. Set this appropriately for other toolchains,
           for example '-@' for the diab compiler or '-via' for ARM toolchain.

       TEMPFILESUFFIX
           The suffix used for the temporary file name used for long command
           lines. The name should include the dot ('.') if one is wanted as it
           will not be added automatically. The default is '.lnk'.

       TEX
           The TeX formatter and typesetter.

       TEXCOM
           The command line used to call the TeX formatter and typesetter.

       TEXCOMSTR
           The string displayed when calling the TeX formatter and typesetter.
           If this is not set, then $TEXCOM (the command line) is displayed.

               env = Environment(TEXCOMSTR = "Building $TARGET from TeX input $SOURCES")

       TEXFLAGS
           General options passed to the TeX formatter and typesetter.

       TEXINPUTS
           List of directories that the LaTeX program will search for include
           directories. The LaTeX implicit dependency scanner will search
           these directories for \include and \import files.

       TEXTFILEPREFIX
           The prefix used for Textfile file names, an empty string by
           default.

       TEXTFILESUFFIX
           The suffix used for Textfile file names; .txt by default.

       TOOLS
           A list of the names of the Tool specifications that are part of
           this construction environment.

       UNCHANGED_SOURCES
           A reserved variable name that may not be set or used in a
           construction environment. (See the manpage section "Variable
           Substitution" for more information).

       UNCHANGED_TARGETS
           A reserved variable name that may not be set or used in a
           construction environment. (See the manpage section "Variable
           Substitution" for more information).

       VENDOR
           The person or organization who supply the packaged software. This
           is used to fill in the Vendor: field in the controlling information
           for RPM packages, and the Manufacturer: field in the controlling
           information for MSI packages.

           See the Package builder.

       VERSION
           The version of the project, specified as a string.

           See the Package builder.

       VSWHERE
           Specify the location of vswhere.exe.

           The vswhere.exe executable is distributed with Microsoft Visual
           Studio and Build Tools since the 2017 edition, but is also
           available standalone. It provides full information about
           installations of 2017 and later editions. With the -legacy
           argument, vswhere.exe can detect installations of the 2010 through
           2015 editions with limited data returned. If VSWHERE is set, SCons
           will use that location.

           Otherwise SCons will look in the following locations and set
           VSWHERE to the path of the first vswhere.exe located.

           o   %ProgramFiles(x86)%\Microsoft Visual Studio\Installer

           o   %ProgramFiles%\Microsoft Visual Studio\Installer

           o   %ChocolateyInstall%\bin

           Note that VSWHERE must be set at the same time or prior to any of
           msvc, msvs , and/or mslink Tool being initialized. Either set it as
           follows

               env = Environment(VSWHERE='c:/my/path/to/vswhere')

           or if your construction environment is created specifying an empty
           tools list (or a list of tools which omits all of default, msvs,
           msvc, and mslink), and also before env.Tool is called to
           ininitialize any of those tools:

                   env = Environment(tools=[])
                   env['VSWHERE'] = r'c:/my/vswhere/install/location/vswhere.exe'
                   env.Tool('msvc')
                   env.Tool('mslink')
                   env.Tool('msvs')



       WINDOWS_EMBED_MANIFEST
           Set to True to embed the compiler-generated manifest (normally
           ${TARGET}.manifest) into all Windows executables and DLLs built
           with this environment, as a resource during their link step. This
           is done using $MT and $MTEXECOM and $MTSHLIBCOM. See also
           $WINDOWS_INSERT_MANIFEST.

       WINDOWS_INSERT_DEF
           If set to true, a library build of a Windows shared library (.dll
           file) will include a reference to the corresponding
           module-definition file at the same time, if a module-definition
           file is not already listed as a build target. The name of the
           module-definition file will be constructed from the base name of
           the library and the construction variables $WINDOWSDEFSUFFIX and
           $WINDOWSDEFPREFIX. The default is to not add a module-definition
           file. The module-definition file is not created by this directive,
           and must be supplied by the developer.

       WINDOWS_INSERT_MANIFEST
           If set to true, scons will add the manifest file generated by
           Microsoft Visual C++ 8.0 and later to the target list so SCons will
           be aware they were generated. In the case of an executable, the
           manifest file name is constructed using $WINDOWSPROGMANIFESTSUFFIX
           and $WINDOWSPROGMANIFESTPREFIX. In the case of a shared library,
           the manifest file name is constructed using
           $WINDOWSSHLIBMANIFESTSUFFIX and $WINDOWSSHLIBMANIFESTPREFIX. See
           also $WINDOWS_EMBED_MANIFEST.

       WINDOWSDEFPREFIX
           The prefix used for a Windows linker module-definition file name.
           Defaults to empty.

       WINDOWSDEFSUFFIX
           The suffix used for a Windows linker module-definition file name.
           Defaults to .def.

       WINDOWSEXPPREFIX
           The prefix used for Windows linker exports file names. Defaults to
           empty.

       WINDOWSEXPSUFFIX
           The suffix used for Windows linker exports file names. Defaults to
           .exp.

       WINDOWSPROGMANIFESTPREFIX
           The prefix used for executable program manifest files generated by
           Microsoft Visual C/C++. Defaults to empty.

       WINDOWSPROGMANIFESTSUFFIX
           The suffix used for executable program manifest files generated by
           Microsoft Visual C/C++. Defaults to .manifest.

       WINDOWSSHLIBMANIFESTPREFIX
           The prefix used for shared library manifest files generated by
           Microsoft Visual C/C++. Defaults to empty.

       WINDOWSSHLIBMANIFESTSUFFIX
           The suffix used for shared library manifest files generated by
           Microsoft Visual C/C++. Defaults to .manifest.

       X_IPK_DEPENDS
           This is used to fill in the Depends: field in the controlling
           information for Ipkg packages.

           See the Package builder.

       X_IPK_DESCRIPTION
           This is used to fill in the Description: field in the controlling
           information for Ipkg packages. The default value is
           "$SUMMARY\n$DESCRIPTION"

       X_IPK_MAINTAINER
           This is used to fill in the Maintainer: field in the controlling
           information for Ipkg packages.

       X_IPK_PRIORITY
           This is used to fill in the Priority: field in the controlling
           information for Ipkg packages.

       X_IPK_SECTION
           This is used to fill in the Section: field in the controlling
           information for Ipkg packages.

       X_MSI_LANGUAGE
           This is used to fill in the Language: attribute in the controlling
           information for MSI packages.

           See the Package builder.

       X_MSI_LICENSE_TEXT
           The text of the software license in RTF format. Carriage return
           characters will be replaced with the RTF equivalent \\par.

           See the Package builder.

       X_MSI_UPGRADE_CODE
           TODO

       X_RPM_AUTOREQPROV
           This is used to fill in the AutoReqProv: field in the RPM .spec
           file.

           See the Package builder.

       X_RPM_BUILD
           internal, but overridable

       X_RPM_BUILDREQUIRES
           This is used to fill in the BuildRequires: field in the RPM .spec
           file. Note this should only be used on a host managed by rpm as the
           dependencies will not be resolvable at build time otherwise.

       X_RPM_BUILDROOT
           internal, but overridable

       X_RPM_CLEAN
           internal, but overridable

       X_RPM_CONFLICTS
           This is used to fill in the Conflicts: field in the RPM .spec file.

       X_RPM_DEFATTR
           This value is used as the default attributes for the files in the
           RPM package. The default value is "(-,root,root)".

       X_RPM_DISTRIBUTION
           This is used to fill in the Distribution: field in the RPM .spec
           file.

       X_RPM_EPOCH
           This is used to fill in the Epoch: field in the RPM .spec file.

       X_RPM_EXCLUDEARCH
           This is used to fill in the ExcludeArch: field in the RPM .spec
           file.

       X_RPM_EXLUSIVEARCH
           This is used to fill in the ExclusiveArch: field in the RPM .spec
           file.

       X_RPM_EXTRADEFS
           A list used to supply extra defintions or flags to be added to the
           RPM .spec file. Each item is added as-is with a carriage return
           appended. This is useful if some specific RPM feature not otherwise
           anticipated by SCons needs to be turned on or off. Note if this
           variable is omitted, SCons will by default supply the value
           '%global debug_package %{nil}' to disable debug package generation.
           To enable debug package generation, include this variable set
           either to None, or to a custom list that does not include the
           default line. Added in version 3.1.

               env.Package(
                   NAME="foo",
                   ...
                   X_RPM_EXTRADEFS=[
                       "%define _unpackaged_files_terminate_build 0"
                       "%define _missing_doc_files_terminate_build 0"
                   ],
                   ...
               )

       X_RPM_GROUP
           This is used to fill in the Group: field in the RPM .spec file.

       X_RPM_GROUP_lang
           This is used to fill in the Group(lang): field in the RPM .spec
           file. Note that lang is not literal and should be replaced by the
           appropriate language code.

       X_RPM_ICON
           This is used to fill in the Icon: field in the RPM .spec file.

       X_RPM_INSTALL
           internal, but overridable

       X_RPM_PACKAGER
           This is used to fill in the Packager: field in the RPM .spec file.

       X_RPM_POSTINSTALL
           This is used to fill in the %post: section in the RPM .spec file.

       X_RPM_POSTUNINSTALL
           This is used to fill in the %postun: section in the RPM .spec file.

       X_RPM_PREFIX
           This is used to fill in the Prefix: field in the RPM .spec file.

       X_RPM_PREINSTALL
           This is used to fill in the %pre: section in the RPM .spec file.

       X_RPM_PREP
           internal, but overridable

       X_RPM_PREUNINSTALL
           This is used to fill in the %preun: section in the RPM .spec file.

       X_RPM_PROVIDES
           This is used to fill in the Provides: field in the RPM .spec file.

       X_RPM_REQUIRES
           This is used to fill in the Requires: field in the RPM .spec file.

       X_RPM_SERIAL
           This is used to fill in the Serial: field in the RPM .spec file.

       X_RPM_URL
           This is used to fill in the Url: field in the RPM .spec file.

       XGETTEXT
           Path to xgettext(1) program (found via Detect()). See xgettext tool
           and POTUpdate builder.

       XGETTEXTCOM
           Complete xgettext command line. See xgettext tool and POTUpdate
           builder.

       XGETTEXTCOMSTR
           A string that is shown when xgettext(1) command is invoked
           (default: '', which means "print $XGETTEXTCOM"). See xgettext tool
           and POTUpdate builder.

       _XGETTEXTDOMAIN
           Internal "macro". Generates xgettext domain name form source and
           target (default: '${TARGET.filebase}').

       XGETTEXTFLAGS
           Additional flags to xgettext(1). See xgettext tool and POTUpdate
           builder.

       XGETTEXTFROM
           Name of file containing list of xgettext(1)'s source files.
           Autotools' users know this as POTFILES.in so they will in most
           cases set XGETTEXTFROM="POTFILES.in" here. The $XGETTEXTFROM files
           have same syntax and semantics as the well known GNU POTFILES.in.
           See xgettext tool and POTUpdate builder.

       _XGETTEXTFROMFLAGS
           Internal "macro". Genrates list of -D<dir> flags from the
           $XGETTEXTPATH list.

       XGETTEXTFROMPREFIX
           This flag is used to add single $XGETTEXTFROM file to xgettext(1)'s
           commandline (default: '-f').

       XGETTEXTFROMSUFFIX
           (default: '')

       XGETTEXTPATH
           List of directories, there xgettext(1) will look for source files
           (default: []).

               Note
               This variable works only together with $XGETTEXTFROM
           See also xgettext tool and POTUpdate builder.

       _XGETTEXTPATHFLAGS
           Internal "macro". Generates list of -f<file> flags from
           $XGETTEXTFROM.

       XGETTEXTPATHPREFIX
           This flag is used to add single search path to xgettext(1)'s
           commandline (default: '-D').

       XGETTEXTPATHSUFFIX
           (default: '')

       YACC
           The parser generator.

       YACCCOM
           The command line used to call the parser generator to generate a
           source file.

       YACCCOMSTR
           The string displayed when generating a source file using the parser
           generator. If this is not set, then $YACCCOM (the command line) is
           displayed.

               env = Environment(YACCCOMSTR = "Yacc'ing $TARGET from $SOURCES")

       YACCFLAGS
           General options passed to the parser generator. If $YACCFLAGS
           contains a -d option, SCons assumes that the call will also create
           a .h file (if the yacc source file ends in a .y suffix) or a .hpp
           file (if the yacc source file ends in a .yy suffix)

       YACCHFILESUFFIX
           The suffix of the C header file generated by the parser generator
           when the -d option is used. Note that setting this variable does
           not cause the parser generator to generate a header file with the
           specified suffix, it exists to allow you to specify what suffix the
           parser generator will use of its own accord. The default value is
           .h.

       YACCHXXFILESUFFIX
           The suffix of the C++ header file generated by the parser generator
           when the -d option is used. Note that setting this variable does
           not cause the parser generator to generate a header file with the
           specified suffix, it exists to allow you to specify what suffix the
           parser generator will use of its own accord. The default value is
           .hpp, except on Mac OS X, where the default is ${TARGET.suffix}.h.
           because the default bison parser generator just appends .h to the
           name of the generated C++ file.

       YACCVCGFILESUFFIX
           The suffix of the file containing the VCG grammar automaton
           definition when the --graph= option is used. Note that setting this
           variable does not cause the parser generator to generate a VCG file
           with the specified suffix, it exists to allow you to specify what
           suffix the parser generator will use of its own accord. The default
           value is .vcg.

       ZIP
           The zip compression and file packaging utility.

       ZIP_OVERRIDE_TIMESTAMP
           An optional timestamp which overrides the last modification time of
           the file when stored inside the Zip archive. This is a tuple of six
           values: Year (>= 1980) Month (one-based) Day of month (one-based)
           Hours (zero-based) Minutes (zero-based) Seconds (zero-based)

       ZIPCOM
           The command line used to call the zip utility, or the internal
           Python function used to create a zip archive.

       ZIPCOMPRESSION
           The compression flag from the Python zipfile module used by the
           internal Python function to control whether the zip archive is
           compressed or not. The default value is zipfile.ZIP_DEFLATED, which
           creates a compressed zip archive. This value has no effect if the
           zipfile module is unavailable.

       ZIPCOMSTR
           The string displayed when archiving files using the zip utility. If
           this is not set, then $ZIPCOM (the command line or internal Python
           function) is displayed.

               env = Environment(ZIPCOMSTR = "Zipping $TARGET")

       ZIPFLAGS
           General options passed to the zip utility.

       ZIPROOT
           An optional zip root directory (default empty). The filenames
           stored in the zip file will be relative to this directory, if
           given. Otherwise the filenames are relative to the current
           directory of the command. For instance:

               env = Environment()
               env.Zip('foo.zip', 'subdir1/subdir2/file1', ZIPROOT='subdir1')

           will produce a zip file foo.zip containing a file with the name
           subdir2/file1 rather than subdir1/subdir2/file1.

       ZIPSUFFIX
           The suffix used for zip file names.

   Configure Contexts
       SCons supports a configure context, an integrated mechanism similar to
       the various AC_CHECK macros in GNU Autoconf for testing the existence
       of external items needed for the build, such as C header files,
       libraries, etc. The mechanism is portable across platforms.

       scons does not maintain an explicit cache of the tested values (this is
       different than Autoconf), but uses its normal dependency tracking to
       keep the checked values up to date. However, users may override this
       behaviour with the --config command line option.

       Configure(env, [custom_tests, conf_dir, log_file, config_h, clean,
       help]), env.Configure([custom_tests, conf_dir, log_file, config_h,
       clean, help])
           Create a configure context, which tracks information discovered
           while running tests. The context includes a local construction
           environment (available as context.env) which is used when running
           the tests and which can be updated with the check results. Only one
           context may be active at a time (since 4.0, scons will raise an
           exception on an attempt to create a new context when there is an
           active context), but a new context can be created after the active
           one is completed. For the global function form, the required env
           describes the initial values for the context's local construction
           environment; for the construction environment method form the
           instance provides the values.

           custom_tests specifies a dictionary containing custom tests (see
           the section on custom tests below). The default value is None,
           meaning no custom tests are added to the configure context.


           conf_dir specifies a directory where the test cases are built. This
           directory is not used for building normal targets. The default
           value is "#/.sconf_temp".


           log_file specifies a file which collects the output from commands
           that are executed to check for the existence of header files,
           libraries, etc. The default is "#/config.log". If you are using the
           VariantDir function, you may want to specify a subdirectory under
           your variant directory.


           config_h specifies a C header file where the results of tests will
           be written. The results will consist of lines like #define
           HAVE_STDIO_H, #define HAVE_LIBM, etc. Customarily, the name chosen
           is "config.h". The default is to not write a config_h file. You can
           specify the same config_h file in multiple calls to Configure, in
           which case SCons will concatenate all results in the specified
           file. Note that SCons uses its normal dependency checking to decide
           if it's necessary to rebuild the specified config_h file. This
           means that the file is not necessarily re-built each time scons is
           run, but is only rebuilt if its contents will have changed and some
           target that depends on the config_h file is being built.

           The clean and help arguments can be used to suppress execution of
           the configuration tests when the -c/--clean or -H/-h/--help options
           are used, respectively. The default behavior is always to execute
           configure context tests, since the results of the tests may affect
           the list of targets to be cleaned or the help text. If the
           configure tests do not affect these, then you may add the
           clean=False or help=False arguments (or both) to avoid unnecessary
           test execution.

       SConf.Finish(context), context.Finish()
           This method must be called after configuration is done. Though
           required, this is not enforced except if Configure is called again
           while there is still an active context, in which case an exception
           is raised.  Finish returns the environment as modified during the
           course of running the configuration checks. After this method is
           called, no further checks can be performed with this configuration
           context. However, you can create a new configure context to perform
           additional checks.

       Example of a typical Configure usage:

           env = Environment()
           conf = Configure(env)
           if not conf.CheckCHeader("math.h"):
               print("We really need math.h!")
               Exit(1)
           if conf.CheckLibWithHeader("qt", "qapp.h", "c++", "QApplication qapp(0,0);"):
               # do stuff for qt - usage, e.g.
               conf.env.Append(CPPDEFINES="WITH_QT")
           env = conf.Finish()

       A configure context has the following predefined methods which can be
       used to perform checks. Where language is a required or optional
       parameter, the choice can currently be C or C++. The spellings accepted
       for C are "C" or "c"; for C++ the value can be "CXX", "cxx", "C++" or
       "c++".

       SConf.CheckHeader(context, header, [include_quotes, language]),
       context.CheckHeader(header, [include_quotes, language])
           Checks if header is usable in the specified language.  header may
           be a list, in which case the last item in the list is the header
           file to be checked, and the previous list items are header files
           whose #include lines should precede the header line being checked
           for. The optional argument include_quotes must be a two character
           string, where the first character denotes the opening quote and the
           second character denotes the closing quote. By default, both
           characters are " (double quote). The optional argument language
           should be either C or C++ and selects the compiler to be used for
           the check. Returns a boolean indicating success or failure.

       SConf.CheckCHeader(context, header, [include_quotes]),
       context.CheckCHeader(header, [include_quotes])
           This is a wrapper around SConf.CheckHeader which checks if header
           is usable in the C language.  header may be a list, in which case
           the last item in the list is the header file to be checked, and the
           previous list items are header files whose #include lines should
           precede the header line being checked for. The optional argument
           include_quotes must be a two character string, where the first
           character denotes the opening quote and the second character
           denotes the closing quote. By default, both characters are "
           (double quote). Returns a boolean indicating success or failure.

       SConf.CheckCXXHeader(context, header, [include_quotes]),
       context.CheckCXXHeader(header, [include_quotes])
           This is a wrapper around SConf.CheckHeader which checks if header
           is usable in the C++ language.  header may be a list, in which case
           the last item in the list is the header file to be checked, and the
           previous list items are header files whose #include lines should
           precede the header line being checked for. The optional argument
           include_quotes must be a two character string, where the first
           character denotes the opening quote and the second character
           denotes the closing quote. By default, both characters are "
           (double quote). Returns a boolean indicating success or failure.

       SConf.CheckFunc(context, function_name, [header, language]),
       context.CheckFunc(function_name, [header, language])
           Checks if the specified C or C++ library function is available
           based on the context's local environment settings (that is, using
           the values of CFLAGS, CPPFLAGS, LIBS or other relevant construction
           variables).


           function_name is the name of the function to check for. The
           optional header argument is a string that will be placed at the top
           of the test file that will be compiled to check if the function
           exists; the default is:

               #ifdef __cplusplus
               extern "C"
               #endif
               char function_name();

           Returns an empty string on success, a string containing an error
           message on failure.

       SConf.CheckLib(context, [library, symbol, header, language,
       autoadd=True]), context.CheckLib([library, symbol, header, language,
       autoadd=True])
           Checks if library provides symbol. If autoadd is true (the default)
           and the library provides the specified symbol, appends the library
           to the LIBS construction variable library may also be None (the
           default), in which case symbol is checked with the current LIBS
           variable, or a list of library names, in which case each library in
           the list will be checked for symbol. If symbol is not set or is
           None, then SConf.CheckLib just checks if you can link against the
           specified library. Note though it is legal syntax, it would not be
           very useful to call this method with library and symbol both
           omitted or None. Returns a boolean indicating success or failure.

       SConf.CheckLibWithHeader(context, library, header, language, [call,
       autoadd=True]), context.CheckLibWithHeader(library, header, language,
       [call, autoadd=True])
           Provides a more sophisticated way to check against libraries then
           the SConf.CheckLib call.  library specifies the library or a list
           of libraries to check.  header specifies a header to check for.
           header may be a list, in which case the last item in the list is
           the header file to be checked, and the previous list items are
           header files whose #include lines should precede the header line
           being checked for.  call can be any valid expression (with a
           trailing ';'). If call is not set, the default simply checks that
           you can link against the specified library.  autoadd (default true)
           specifies whether to add the library to the environment if the
           check succeeds. Returns a boolean indicating success or failure.

       SConf.CheckType(context, type_name, [includes, language]),
       context.CheckType(type_name, [includes, language])
           Checks for the existence of a type defined by typedef.  type_name
           specifies the typedef name to check for.  includes is a string
           containing one or more #include lines that will be inserted into
           the program that will be run to test for the existence of the type.
           Example:

               sconf.CheckType('foo_type', '#include "my_types.h"', 'C++')

           Returns an empty string on success, a string containing an error
           message on failure.

       SConf.CheckCC(context), context.CheckCC()
           Checks whether the C compiler (as defined by the CC construction
           variable) works by trying to compile a small source file. Returns a
           boolean indicating success or failure.

           By default, SCons only detects if there is a program with the
           correct name, not if it is a functioning compiler.

           This uses the exact same command as the one used by the object
           builder for C source files, so it can be used to detect if a
           particular compiler flag works or not.

       SConf.CheckCXX(context), context.CheckCXX()
           Checks whether the C++ compiler (as defined by the CXX construction
           variable) works by trying to compile a small source file. By
           default, SCons only detects if there is a program with the correct
           name, not if it is a functioning compiler. Returns a boolean
           indicating success or failure.

           This uses the exact same command as the one used by the object
           builder for C++ source files, so it can be used to detect if a
           particular compiler flag works or not.

       SConf.CheckSHCC(context), context.CheckSHCC()
           Checks whether the shared-object C compiler (as defined by the SHCC
           construction variable) works by trying to compile a small source
           file. By default, SCons only detects if there is a program with the
           correct name, not if it is a functioning compiler. Returns a
           boolean indicating success or failure.

           This uses the exact same command as the one used by the object
           builder for C source file, so it can be used to detect if a
           particular compiler flag works or not. This does not check whether
           the object code can be used to build a shared library, only that
           the compilation (not link) succeeds.

       SConf.CheckSHCXX(context), context.CheckSHCXX()
           Checks whether the shared-object C++ compiler (as defined by the
           SHCXX construction variable) works by trying to compile a small
           source file. By default, SCons only detects if there is a program
           with the correct name, not if it is a functioning compiler. Returns
           a boolean indicating success or failure.

           This uses the exact same command as the one used by the object
           builder for C++ source files, so it can be used to detect if a
           particular compiler flag works or not. This does not check whether
           the object code can be used to build a shared library, only that
           the compilation (not link) succeeds.

       SConf.CheckTypeSize(context, type_name, [header, language, expect]),
       context.CheckTypeSize(type_name, [header, language, expect])
           Checks for the size of a type defined by typedef.  type_name
           specifies the typedef name to check for. The optional header
           argument is a string that will be placed at the top of the test
           file that will be compiled to check if the type exists; the default
           is empty. If the optional expect, is supplied, it should be an
           integer size; CheckTypeSize will fail unless type_name is actually
           that size. Returns the size in bytes, or zero if the type was not
           found (or if the size did not match expect).

           For example,

               CheckTypeSize('short', expect=2)

           will return the size 2 only if short is actually two bytes.

       SConf.CheckDeclaration(context, symbol, [includes, language]),
       context.CheckDeclaration(symbol, [includes, language])
           Checks if the specified symbol is declared.  includes is a string
           containing one or more #include lines that will be inserted into
           the program that will be run to test for the existence of the
           symbol. Returns a boolean indicating success or failure.

       SConf.Define(context, symbol, [value, comment]), context.Define(symbol,
       [value, comment])
           This function does not check for anything, but defines a
           preprocessor symbol that will be added to the configuration header
           file. It is the equivalent of AC_DEFINE, and defines the symbol
           name with the optional value and the optional comment comment.

           Define Examples:

               env = Environment()
               conf = Configure(env)

               # Puts the following line in the config header file:
               #    #define A_SYMBOL
               conf.Define("A_SYMBOL")

               # Puts the following line in the config header file:
               #    #define A_SYMBOL 1
               conf.Define("A_SYMBOL", 1)

           Be careful about quoting string values, though:

               env = Environment()
               conf = Configure(env)

               # Puts the following line in the config header file:
               #    #define A_SYMBOL YA
               conf.Define("A_SYMBOL", "YA")

               # Puts the following line in the config header file:
               #    #define A_SYMBOL "YA"
               conf.Define("A_SYMBOL", '"YA"')

           For comment:

               env = Environment()
               conf = Configure(env)

               # Puts the following lines in the config header file:
               #    /* Set to 1 if you have a symbol */
               #    #define A_SYMBOL 1
               conf.Define("A_SYMBOL", 1, "Set to 1 if you have a symbol")

       You can define your own custom checks in addition to the predefined
       checks. You pass a dictionary of these to the Configure function as the
       custom_tests argument. This dictionary maps the names of the checks to
       the user defined Python callables (either Python functions or class
       instances implementing a __call__ method). Each custom check will be
       called with a first argument of a CheckContext, instance followed by
       the arguments, which must be supplied by the user of the check. A
       CheckContext instance defines the following methods:

       context.Message(text)
           Displays a message, as an indicator of progess.  text will be
           displayed, e.g.  Checking for library X.... Usually called before
           the check is started.

       context.Result(res)
           Displays a "result" message, as an indicator of progress.  res can
           be either an integer or a string. If an integer, displays yes (if
           res evaluates True) or no (if res evaluates False). If a string, it
           is displayed as-is. Usually called after the check has completed.

       context.TryCompile(text, extension='')
           Checks if a file with the specified extension (e.g. '.c')
           containing text can be compiled using the environment's Object
           builder. Returns a boolean indicating success or failure.

       context.TryLink(text, extension='')
           Checks, if a file with the specified extension (e.g. '.c')
           containing text can be compiled using the environment's Program
           builder. Returns a boolean indicating success or failure.

       context.TryRun(text, extension='')
           Checks if a file with the specified extension (e.g. '.c')
           containing text can be compiled using the environment's Program
           builder. On success, the program is run. If the program executes
           successfully (that is, its return status is 0), a tuple (1,
           outputStr) is returned, where outputStr is the standard output of
           the program. If the program fails execution (its return status is
           non-zero), then (0, '') is returned.

       context.TryAction(action, [text, extension=''])
           Checks if the specified action with an optional source file
           (contents text, extension extension) can be executed.  action may
           be anything which can be converted to a scons Action. On success,
           (1, outputStr) is returned, where outputStr is the content of the
           target file. On failure (0, '') is returned.

       context.TryBuild(builder[, text, extension=''])
           Low level implementation for testing specific builds; the methods
           above are based on this method. Given the Builder instance builder
           and the optional text of a source file with optional extension,
           returns a boolean indicating success or failure. In addition,
           context.lastTarget is set to the build target node if the build was
           successful.

       Example of implementing and using custom tests:

           def CheckQt(context, qtdir):
               context.Message( 'Checking for qt ...' )
               lastLIBS = context.env['LIBS']
               lastLIBPATH = context.env['LIBPATH']
               lastCPPPATH= context.env['CPPPATH']
               context.env.Append(LIBS='qt', LIBPATH=qtdir + '/lib', CPPPATH=qtdir + '/include')
               ret = context.TryLink("""
           #include <qapp.h>
           int main(int argc, char **argv) {
             QApplication qapp(argc, argv);
             return 0;
           }
           """)
               if not ret:
                   context.env.Replace(LIBS=lastLIBS, LIBPATH=lastLIBPATH, CPPPATH=lastCPPPATH)
               context.Result( ret )
               return ret

           env = Environment()
           conf = Configure(env, custom_tests={'CheckQt': CheckQt})
           if not conf.CheckQt('/usr/lib/qt'):
               print('We really need qt!')
               Exit(1)
           env = conf.Finish()

   Command-Line Construction Variables
       Often when building software, some variables need to be specified at
       build time. For example, libraries needed for the build may be in
       non-standard locations, or site-specific compiler options may need to
       be passed to the compiler.  SCons provides a Variables object to
       support overriding construction variables with values obtained from
       various sources, often from the command line:

           scons VARIABLE=foo

       The variable values can also be specified in a configuration file or an
       SConscript file.

       To obtain the object for manipulating values, call the Variables
       function:

       Variables([files, [args]])
           If files is a file or list of files, those are executed as Python
           scripts, and the values of (global) Python variables set in those
           files are added as construction variables in the Default
           Environment. If no files are specified, or the files argument is
           None, then no files will be read (supplying None is necessary if
           there are no files but you want to specify args as a positional
           argument).

           The following example file contents could be used to set an
           alternative C compiler:

               CC = 'my_cc'

           If args is specified, it is a dictionary of values that will
           override anything read from files. This is primarily intended to
           pass the ARGUMENTS dictionary that holds variables specified on the
           command line. Example:

               vars = Variables('custom.py')
               vars = Variables('overrides.py', ARGUMENTS)
               vars = Variables(None, {FOO:'expansion', BAR:7})

           Calling Variables with no arguments is equivalent to:

               vars = Variables(files=None, args=ARGUMENTS)

           Note that since the variables are eventually added as construction
           variables, you should choose variable names which do not
           unintentionally change pre-defined construction variables that your
           project will make use of (see the section called "Construction
           Variables").

       Variables objects have the following methods:

       vars.Add(key, [help, default, validator, converter])
           Add a customizable construction variable to the Variables object.
           key is the name of the variable.  help is the help text for the
           variable.  default is the default value of the variable; if the
           default value is None and there is no explicit value specified, the
           construction variable will not be added to the construction
           environment. If set, validator is called to validate the value of
           the variable. A function supplied as a validator shall accept
           arguments: key, value, and env. The recommended way to handle an
           invalid value is to raise an exception (see example below). If set,
           converter is called to convert the value before putting it in the
           environment, and should take either a value, or the value and
           environment, as parameters. The converter function must return a
           value, which will be converted into a string before being validated
           by the validator (if any) and then added to the construction
           environment.

           Examples:

               vars.Add('CC', help='The C compiler')

               def valid_color(key, val, env):
                   if not val in ['red', 'blue', 'yellow']:
                       raise Exception("Invalid color value '%s'" % val)

               vars.Add('COLOR', validator=valid_color)

       vars.AddVariables(args)
           A convenience method that adds multiple customizable construction
           variables to a Variables object in one call; equivalent to calling
           Add multiple times. The args are tuples (or lists) that contain the
           arguments for an individual call to the Add method. Since tuples
           are not Python mappings, the arguments cannot use the keyword form,
           but rather are positional arguments as documented for Add: a
           required name, the rest optional but must be in the specified in
           order if used.

               opt.AddVariables(
                   ("debug", "", 0),
                   ("CC", "The C compiler"),
                   ("VALIDATE", "An option for testing validation", "notset", validator, None),
               )

       vars.Update(env, [args])
           Update a construction environment env with the customized
           construction variables . Any specified variables that are not
           configured for the Variables object will be saved and may be
           retrieved using the UnknownVariables method, below.

           Normally this method is not called directly, but rather invoked
           indirectly by passing the Variables object to the Environment
           function:

               env = Environment(variables=vars)

       vars.UnknownVariables()
           Returns a dictionary containing any variables that were specified
           either in the files or the dictionary with which the Variables
           object was initialized, but for which the Variables object was not
           configured.

               env = Environment(variables=vars)
               for key, value in vars.UnknownVariables():
                   print("unknown variable:  %s=%s" % (key, value))

       vars.Save(filename, env)
           Save the currently set variables into a script file named by
           filename that can be used on the next invocation to automatically
           load the current settings. This method combined with the Variables
           method can be used to support caching of variables between runs.

               env = Environment()
               vars = Variables(['variables.cache', 'custom.py'])
               vars.Add(...)
               vars.Update(env)
               vars.Save('variables.cache', env)

       vars.GenerateHelpText(env, [sort])
           Generate help text documenting the customizable construction
           variables, suitable for passing in to the Help function.  env is
           the construction environment that will be used to get the actual
           values of the customizable variables. If the (optional) value of
           sort is callable, it is used as a comparison function to determine
           how to sort the added variables. This function must accept two
           arguments, compare them, and return a negative integer if the first
           is less-than the second, zero for equality, or a positive integer
           for greater-than. Optionally a Boolean value of True for sort will
           cause a standard alphabetical sort to be performed.

               Help(vars.GenerateHelpText(env))

               def cmp(a, b):
                   return (a > b) - (a < b)

               Help(vars.GenerateHelpText(env, sort=cmp))

       vars.FormatVariableHelpText(env, opt, help, default, actual)
           Returns a formatted string containing the printable help text for
           one option. It is normally not called directly, but is called by
           the GenerateHelpText method to create the returned help text. It
           may be overridden with your own function that takes the arguments
           specified above and returns a string of help text formatted to your
           liking. Note that GenerateHelpText will not put any blank lines or
           extra characters in between the entries, so you must add those
           characters to the returned string if you want the entries
           separated.

               def my_format(env, opt, help, default, actual):
                   fmt = "\n%s: default=%s actual=%s (%s)\n"
                   return fmt % (opt, default, actual, help)
               vars.FormatVariableHelpText = my_format

       To make it more convenient to work with customizable Variables, scons
       provides a number of functions that make it easy to set up various
       types of Variables. Each of these return a tuple ready to be passed to
       the Add or AddVariables method:

       BoolVariable(key, help, default)
           Returns a tuple of arguments to set up a Boolean option. The option
           will use the specified name key, have a default value of default,
           and help will form the descriptive part of the help text. The
           option will interpret the values y, yes, t, true, 1, on and all as
           true, and the values n, no, f, false, 0, off and none as false.

       EnumVariable(key, help, default, allowed_values, [map, ignorecase])
           Returns a tuple of arguments to set up an option whose value may be
           one of a specified list of legal enumerated values. The option will
           use the specified name key, have a default value of default, and
           help will form the descriptive part of the help text. The option
           will only support those values in the allowed_values list. The
           optional map argument is a dictionary that can be used to convert
           input values into specific legal values in the allowed_values list.
           If the value of ignore_case is 0 (the default), then the values are
           case-sensitive. If the value of ignore_case is 1, then values will
           be matched case-insensitively. If the value of ignore_case is 2,
           then values will be matched case-insensitively, and all input
           values will be converted to lower case.

       ListVariable(key, help, default, names, [map])
           Returns a tuple of arguments to set up an option whose value may be
           one or more of a specified list of legal enumerated values. The
           option will use the specified name key, have a default value of
           default, and help will form the descriptive part of the help text.
           The option will only accept the values "all", "none", or the values
           in the names list. More than one value may be specified, separated
           by commas. The default may be a string of comma-separated default
           values, or a list of the default values. The optional map argument
           is a dictionary that can be used to convert input values into
           specific legal values in the names list. (Note that the additional
           values accepted through the use of a map are not reflected in the
           generated help message).

       PackageVariable(key, help, default)
           Returns a tuple of arguments to set up an option whose value is a
           path name of a package that may be enabled, disabled or given an
           explicit path name. The option will use the specified name key,
           have a default value of default, and help will form the descriptive
           part of the help text. The option will support the values yes,
           true, on, enable or search, in which case the specified default
           will be used, or the option may be set to an arbitrary string
           (typically the path name to a package that is being enabled). The
           option will also support the values no, false, off or disable to
           disable use of the specified option.

       PathVariable(key, help, default, [validator])
           Returns a tuple of arguments to set up an option whose value is
           expected to be a path name. The option will use the specified name
           key, have a default value of default, and help will form the
           descriptive part of the help text. An additional validator may be
           specified that will be called to verify that the specified path is
           acceptable. SCons supplies the following ready-made validators:

           PathVariable.PathExists
               Verify that the specified path exists (this the default
               behavior if no validator is supplied).

           PathVariable.PathIsFile
               Verify that the specified path exists and is a regular file.

           PathVariable.PathIsDir
               Verify that the specified path exists and is a directory.

           PathVariable.PathIsDirCreate
               Verify that the specified path exists and is a directory; if it
               does not exist, create the directory.

           PathVariable.PathAccept
               Accept the specific path name argument without validation,
               suitable for when you want your users to be able to specify a
               directory path that will be created as part of the build
               process, for example.

           You may supply your own validator function, which must accept three
           arguments (key, the name of the variable to be set; val, the
           specified value being checked; and env, the construction
           environment) and should raise an exception if the specified value
           is not acceptable.

       These functions make it convenient to create a number of variables with
       consistent behavior in a single call to the AddVariables method:

           vars.AddVariables(
               BoolVariable(
                   "warnings",
                   help="compilation with -Wall and similar",
                   default=1,
               ),
               EnumVariable(
                   "debug",
                   help="debug output and symbols",
                   default="no",
                   allowed_values=("yes", "no", "full"),
                   map={},
                   ignorecase=0,  # case sensitive
               ),
               ListVariable(
                   "shared",
                   help="libraries to build as shared libraries",
                   default="all",
                   names=list_of_libs,
               ),
               PackageVariable(
                   "x11",
                   help="use X11 installed here (yes = search some places)",
                   default="yes",
               ),
               PathVariable(
                   "qtdir",
                   help="where the root of Qt is installed",
                   default=qtdir),
               PathVariable(
                   "foopath",
                   help="where the foo library is installed",
                   default=foopath,
                   validator=PathVariable.PathIsDir,
               ),
           )

   File and Directory Nodes
       The File and Dir functions/methods return File and Directory Nodes,
       respectively. Such nodes are Python objects with several user-visible
       attributes and methods that are often useful to access in SConscript
       files:

       n.path
           The build path of the given file or directory. This path is
           relative to the top-level directory (where the SConstruct file is
           found). The build path is the same as the source path if
           variant_dir is not being used.

       n.abspath
           The absolute build path of the given file or directory.

       n.relpath
           The build path of the given file or directory relative to the root
           SConstruct file's directory.

       n.srcnode()
           The srcnode method returns another File or Directory Node
           representing the source path of the given File or Directory Node.

       For example:

           # Get the current build dir's path, relative to top.
           Dir('.').path
           # Current dir's absolute path
           Dir('.').abspath
           # Current dir's path relative to the root SConstruct file's directory
           Dir('.').relpath
           # Next line is always '.', because it is the top dir's path relative to itself.
           Dir('#.').path
           File('foo.c').srcnode().path   # source path of the given source file.

           # Builders also return File objects:
           foo = env.Program('foo.c')
           print("foo will be built in", foo.path)

       File and Directory Node objects have methods to create File and
       Directory Nodes relative to the original Node.

       If the object is a Directory Node, these methods will place the the new
       Node within the directory the Node represents:

       d.Dir(name)
           Returns a directory Node for a subdirectory of d named name.

       d.File(name)
           Returns a file Node for a file within d named name.

       d.Entry(name)
           Returns an unresolved Node within d named name.

       If the object is a File Node, these methods will place the the new Node
       in the same directory as the one the Node represents:

       f.Dir(name)
           Returns a directory named name within the parent directory of f.

       f.File(name)
           Returns a file named name within the parent directory of f.

       f.Entry(name)
           Returns an unresolved Node named name within the parent directory
           of f.

       For example:

           # Get a Node for a file within a directory
           incl = Dir('include')
           f = incl.File('header.h')

           # Get a Node for a subdirectory within a directory
           dist = Dir('project-3.2.1')
           src = dist.Dir('src')

           # Get a Node for a file in the same directory
           cfile = File('sample.c')
           hfile = cfile.File('sample.h')

           # Combined example
           docs = Dir('docs')
           html = docs.Dir('html')
           index = html.File('index.html')
           css = index.File('app.css')

EXTENDING SCONS
   Builder Objects
       scons can be extended to build different types of targets by adding new
       Builder objects to a construction environment.  In general, you should
       only need to add a new Builder object when you want to build a new type
       of file or other external target. For output file types scons already
       knows about, you can usually modify the behavior of premade Builders
       such as Program, Object or Library by changing the construction
       variables they use ($CC, $LINK, etc.). In this manner you can, for
       example, change the compiler to use, which is simpler and less
       error-prone than writing a new builder. The documentation for each
       Builder lists which construction variables it uses.

       Builder objects are created using the Builder factory function. Once
       created, a builder is added to an environment by entering it in the
       $BUILDERS dictionary in that environment (some of the examples in this
       section illustrate that).

       The Builder function accepts the following keyword arguments:

       action
           The command used to build the target from the source.  action may
           be a string representing a template command line to execute, a list
           of strings representing the command to execute with its arguments
           (suitable for enclosing white space in an argument), a dictionary
           mapping source file name suffixes to any combination of command
           line strings (if the builder should accept multiple source file
           extensions), a Python function, an Action object (see the section
           called "Action Objects") or a list of any of the above.

           An action function must accept three arguments: source, target and
           env.  source is a list of source nodes; target is a list of target
           nodes; env is the construction environment to use for context.

           The action and generator arguments must not both be used for the
           same Builder.

       prefix
           The prefix to prepend to the target file name.  prefix may be a
           string, a function (or other callable) that takes two arguments (a
           construction environment and a list of sources) and returns a
           prefix string, or a dictionary specifying a mapping from a specific
           source suffix (of the first source specified) to a corresponding
           target prefix string. For the dictionary form, both the source
           suffix (key) and target prefix (value) specifications may use
           environment variable substitution, and the target prefix may also
           be a callable object. The default target prefix may be indicated by
           a dictionary entry with a key of None.

               b = Builder("build_it < $SOURCE > $TARGET",
                           prefix="file-")

               def gen_prefix(env, sources):
                   return "file-" + env['PLATFORM'] + '-'

               b = Builder("build_it < $SOURCE > $TARGET",
                           prefix=gen_prefix)

               b = Builder("build_it < $SOURCE > $TARGET",
                           suffix={None: "file-", "$SRC_SFX_A": gen_prefix})

       suffix
           The suffix to append to the target file name. Specified in the same
           manner as for prefix above. If the suffix is a string, then scons
           prepends a '.' to the suffix if it's not already there. The string
           returned by the callable object or obtained from the dictionary is
           untouched and you need to manually prepend a '.' if one is
           required.

               b = Builder("build_it < $SOURCE > $TARGET"
                           suffix="-file")

               def gen_suffix(env, sources):
                   return "." + env['PLATFORM'] + "-file"

               b = Builder("build_it < $SOURCE > $TARGET",
                           suffix=gen_suffix)

               b = Builder("build_it < $SOURCE > $TARGET",
                           suffix={None: ".sfx1", "$SRC_SFX_A": gen_suffix})

       ensure_suffix
           If set to a true value, ensures that targets will end in suffix.
           Thus, the suffix will also be added to any target strings that have
           a suffix that is not already suffix. The default behavior (also
           indicated by a false value) is to leave unchanged any target string
           that looks like it already has a suffix.

               b1 = Builder("build_it < $SOURCE > $TARGET"
                            suffix = ".out")
               b2 = Builder("build_it < $SOURCE > $TARGET"
                            suffix = ".out",
                            ensure_suffix=True)
               env = Environment()
               env['BUILDERS']['B1'] = b1
               env['BUILDERS']['B2'] = b2

               # Builds "foo.txt" because ensure_suffix is not set.
               env.B1('foo.txt', 'foo.in')

               # Builds "bar.txt.out" because ensure_suffix is set.
               env.B2('bar.txt', 'bar.in')

       src_suffix
           The expected source file name suffix.  src_suffix may be a string
           or a list of strings.

       target_scanner
           A Scanner object that will be invoked to find implicit dependencies
           for this target file. This keyword argument should be used for
           Scanner objects that find implicit dependencies based only on the
           target file and the construction environment, not for implicit
           dependencies based on source files. See the section called "Scanner
           Objects" for information about creating Scanner objects.

       source_scanner
           A Scanner object that will be invoked to find implicit dependencies
           in any source files used to build this target file. This is where
           you would specify a scanner to find things like #include lines in
           source files. The pre-built DirScanner Scanner object may be used
           to indicate that this Builder should scan directory trees for
           on-disk changes to files that scons does not know about from other
           Builder or function calls. See the section called "Scanner Objects"
           for information about creating your own Scanner objects.

       target_factory
           A factory function that the Builder will use to turn any targets
           specified as strings into SCons Nodes. By default, SCons assumes
           that all targets are files. Other useful target_factory values
           include Dir, for when a Builder creates a directory target, and
           Entry, for when a Builder can create either a file or directory
           target.

           Example:

               MakeDirectoryBuilder = Builder(action=my_mkdir, target_factory=Dir)
               env = Environment()
               env.Append(BUILDERS={'MakeDirectory': MakeDirectoryBuilder})
               env.MakeDirectory('new_directory', [])

           Note that the call to this MakeDirectory Builder needs to specify
           an empty source list to make the string represent the builder's
           target; without that, it would assume the argument is the source,
           and would try to deduce the target name from it, which in the
           absence of an automatically-added prefix or suffix would lead to a
           matching target and source name and a circular dependency.

       source_factory
           A factory function that the Builder will use to turn any sources
           specified as strings into SCons Nodes. By default, SCons assumes
           that all source are files. Other useful source_factory values
           include Dir, for when a Builder uses a directory as a source, and
           Entry, for when a Builder can use files or directories (or both) as
           sources.

           Example:

               CollectBuilder = Builder(action=my_mkdir, source_factory=Entry)
               env = Environment()
               env.Append(BUILDERS={'Collect': CollectBuilder})
               env.Collect('archive', ['directory_name', 'file_name'])

       emitter
           A function or list of functions to manipulate the target and source
           lists before dependencies are established and the target(s) are
           actually built.  emitter can also be a string containing a
           construction variable to expand to an emitter function or list of
           functions, or a dictionary mapping source file suffixes to emitter
           functions. (Only the suffix of the first source file is used to
           select the actual emitter function from an emitter dictionary.)

           A function passed as emitter must accept three arguments: source,
           target and env.  source is a list of source nodes, target is a list
           of target nodes, env is the construction environment to use for
           context.

           An emitter must return a tuple containing two lists, the list of
           targets to be built by this builder, and the list of sources for
           this builder.

           Example:

               def e(target, source, env):
                   return (target + ['foo.foo'], source + ['foo.src'])

               # Simple association of an emitter function with a Builder.
               b = Builder("my_build < $TARGET > $SOURCE",
                           emitter = e)

               def e2(target, source, env):
                   return (target + ['bar.foo'], source + ['bar.src'])

               # Simple association of a list of emitter functions with a Builder.
               b = Builder("my_build < $TARGET > $SOURCE",
                           emitter = [e, e2])

               # Calling an emitter function through a construction variable.
               env = Environment(MY_EMITTER=e)
               b = Builder("my_build < $TARGET > $SOURCE",
                           emitter='$MY_EMITTER')

               # Calling a list of emitter functions through a construction variable.
               env = Environment(EMITTER_LIST=[e, e2])
               b = Builder("my_build < $TARGET > $SOURCE",
                           emitter='$EMITTER_LIST')

               # Associating multiple emitters with different file
               # suffixes using a dictionary.
               def e_suf1(target, source, env):
                   return (target + ['another_target_file'], source)
               def e_suf2(target, source, env):
                   return (target, source + ['another_source_file'])
               b = Builder("my_build < $TARGET > $SOURCE",
                           emitter={'.suf1' : e_suf1,
                                    '.suf2' : e_suf2})

       multi
           Specifies whether this builder is allowed to be called multiple
           times for the same target file(s). The default is False, which
           means the builder can not be called multiple times for the same
           target file(s). Calling a builder multiple times for the same
           target simply adds additional source files to the target; it is not
           allowed to change the environment associated with the target,
           specify additional environment overrides, or associate a different
           builder with the target.

       env
           A construction environment that can be used to fetch source code
           using this Builder. (Note that this environment is not used for
           normal builds of normal target files, which use the environment
           that was used to call the Builder for the target file.)

       generator
           A function that returns a list of actions that will be executed to
           build the target(s) from the source(s). The returned action(s) may
           be an Action object, or anything that can be converted into an
           Action object (see the next section).

           A function passed as generator must accept four arguments: source,
           target, env and for_signature.  source is a list of source nodes,
           target is a list of target nodes, env is the construction
           environment to use for context, for_signature is a Boolean value
           that specifies whether the generator is being called for generating
           a build signature (as opposed to actually executing the command).

           Example:

               def g(source, target, env, for_signature):
                   return [["gcc", "-c", "-o"] + target + source]

               b = Builder(generator=g)

           The generator and action arguments must not both be used for the
           same Builder.

       src_builder
           Specifies a builder to use when a source file name suffix does not
           match any of the suffixes of the builder. Using this argument
           produces a multi-stage builder.

       single_source
           Specifies that this builder expects exactly one source file per
           call. Giving more than one source file without target files results
           in implicitly calling the builder multiple times (once for each
           source given). Giving multiple source files together with target
           files results in a UserError exception.

       source_ext_match
           When the specified action argument is a dictionary, the default
           behavior when a builder is passed multiple source files is to make
           sure that the extensions of all the source files match. If it is
           legal for this builder to be called with a list of source files
           with different extensions, this check can be suppressed by setting
           source_ext_match to False or some other non-true value. In this
           case, scons will use the suffix of the first specified source file
           to select the appropriate action from the action dictionary.

           In the following example, the setting of source_ext_match prevents
           scons from exiting with an error due to the mismatched suffixes of
           foo.in and foo.extra.

               b = Builder(action={'.in' : 'build $SOURCES > $TARGET'},
                           source_ext_match=False)

               env = Environment(BUILDERS={'MyBuild':b})
               env.MyBuild('foo.out', ['foo.in', 'foo.extra'])

       env
           A construction environment that can be used to fetch source code
           using this Builder. (Note that this environment is not used for
           normal builds of normal target files, which use the environment
           that was used to call the Builder for the target file.)

               b = Builder(action="build < $SOURCE > $TARGET")
               env = Environment(BUILDERS={'MyBuild' : b})
               env.MyBuild('foo.out', 'foo.in', my_arg='xyzzy')

       chdir
           A directory from which scons will execute the action(s) specified
           for this Builder. If the chdir argument is a string or a directory
           Node, scons will change to the specified directory. If the chdir is
           not a string or Node and is non-zero, then scons will change to the
           target file's directory.

           Note that scons will not automatically modify its expansion of
           construction variables like $TARGET and $SOURCE when using the
           chdir keyword argument--that is, the expanded file names will still
           be relative to the top-level directory containing the SConstruct
           file, and consequently incorrect relative to the chdir directory.
           Builders created using chdir keyword argument, will need to use
           construction variable expansions like ${TARGET.file} and
           ${SOURCE.file} to use just the filename portion of the targets and
           source.

               b = Builder(action="build < ${SOURCE.file} > ${TARGET.file}",
                           chdir=1)
               env = Environment(BUILDERS={'MyBuild' : b})
               env.MyBuild('sub/dir/foo.out', 'sub/dir/foo.in')

               Warning
               Python only keeps one current directory location even if there
               are multiple threads. This means that use of the chdir argument
               will not work with the SCons -j option, because individual
               worker threads spawned by SCons interfere with each other when
               they start changing directory.

       Any additional keyword arguments supplied when a Builder object is
       created (that is, when the Builder function is called) will be set in
       the executing construction environment when the Builder object is
       called. The canonical example here would be to set a construction
       variable to the repository of a source code system.

       Any additional keyword arguments supplied when a Builder object is
       called will only be associated with the target created by that
       particular Builder call (and any other files built as a result of the
       call).

       These extra keyword arguments are passed to the following functions:
       command generator functions, function Actions, and emitter functions.

   Action Objects
       The Builder factory function will turn its action keyword argument into
       an appropriate internal Action object, as will the Command function.
       You can also explicitly create Action objects for passing to Builder,
       or other functions that take actions as arguments, by calling the
       Action factory function. This may more efficient when multiple Builder
       objects need to do the same thing rather than letting each of those
       Builder objects create a separate Action object. It also allows more
       flexible configuration of an Action object. For example, to control the
       message printed when the action is taken you need to create the action
       object using Action.

       The Action factory function returns an appropriate object for the
       action represented by the type of the action argument (the first
       positional parmeter):

       o   If action is already an Action object, the object is simply
           returned.

       o   If action is a string, a command-line Action is returned. If such a
           string begins with @, the command line is not printed. If the
           string begins with hyphen (-), the exit status from the specified
           command is ignored, allowing execution to continue even if the
           command reports failure:

               Action('$CC -c -o $TARGET $SOURCES')

               # Doesn't print the line being executed.
               Action('@build $TARGET $SOURCES')

               # Ignores return value
               Action('-build $TARGET $SOURCES')

       o   If action is a list, then a list of Action objects is returned. An
           Action object is created as necessary for each element in the list.
           If an element within the list is itself a list, the embedded list
           is taken as the command and arguments to be executed via the
           command line. This allows white space to be enclosed in an argument
           rather than taken as a separator by defining a command in a list
           within a list:

               Action([['cc', '-c', '-DWHITE SPACE', '-o', '$TARGET', '$SOURCES']])

       o   If action is a callable object, a Function Action is returned. The
           callable must accept three keyword arguments: target, source and
           env.  target is a Node object representing the target file, source
           is a Node object representing the source file and env is the
           construction environment used for building the target file.

           The target and source arguments may be lists of Node objects if
           there is more than one target file or source file. The actual
           target and source file name(s) may be retrieved from their Node
           objects via the built-in Python str function:

               target_file_name = str(target)
               source_file_names = [str(x) for x in source]

           The function should return 0 or None to indicate a successful build
           of the target file(s). The function may raise an exception or
           return a non-zero exit status to indicate an unsuccessful build.

               def build_it(target=None, source=None, env=None):
                   # build the target from the source
                   return 0

               a = Action(build_it)

       o   If action is not one of the above types, no action object is
           generated and Action returns None.

       The environment method form env.Action will expand construction
       variables in any argument strings, including action, at the time it is
       called, using the construction variables in the construction
       environment through which it was called. The global function form
       Action delays variable expansion until the Action object is actually
       used.

       The optional second argument to Action is used to control the output
       which is printed when the Action is actually performed. If this
       parameter is omitted, or if the value is an empty string, a default
       output depending on the type of the action is used. For example, a
       command-line action will print the executed command. The following
       argument types are accepted:

       o   If output is a string, substitution is performed on the string
           before it is printed. The string typically contains variables,
           notably $TARGET(S) and $SOURCE(S), or consists of just a single
           variable, which is optionally defined somewhere else.  SCons itself
           heavily uses the latter variant.

       o   If output is a function, the function will be called to obtain a
           string describing the action being executed. The function must
           accept three keyword arguments: target, source and env, with the
           same interpretation as for a callable action argument above.

       o   If outputis None, output is suppressed entirely.

       Instead of using a positional argument, the cmdstr keyword argument may
       be used to specify the output string, or the strfunction keyword
       argument may be used to specify a function to return the output string.
       cmdstr=None suppresses output entirely.

       Examples:

           def build_it(target, source, env):
               # build the target from the source
               return 0

           def string_it(target, source, env):
               return "building '%s' from '%s'" % (target[0], source[0])

           # Use a positional argument.
           f = Action(build_it, string_it)
           s = Action(build_it, "building '$TARGET' from '$SOURCE'")

           # Alternatively, use a keyword argument.
           f = Action(build_it, strfunction=string_it)
           s = Action(build_it, cmdstr="building '$TARGET' from '$SOURCE'")

           # You can provide a configurable variable.
           l = Action(build_it, '$STRINGIT')

       Any additional positional arguments, if present, may either be
       construction variables or lists of construction variables whose values
       will be included in the signature of the Action when deciding whether a
       target should be rebuilt because the action changed. Such variables may
       also be specified using the varlist keyword parameter; both positional
       and keyword forms may be present, and will be combined. This is
       necessary whenever you want a target to be rebuilt when a specific
       construction variable changes. This is not often needed for a string
       action, as the expanded variables will normally be part of the command
       line, but may be needed if a Python function action uses the value of a
       construction variable when generating the command line.

           def build_it(target, source, env):
               # build the target from the 'XXX' construction variable
               with open(target[0], 'w') as f:
                   f.write(env['XXX'])
               return 0

           # Use positional arguments.
           a = Action(build_it, '$STRINGIT', ['XXX'])

           # Alternatively, use a keyword argument.
           a = Action(build_it, varlist=['XXX'])

       The Action factory function can be passed the following optional
       keyword arguments to modify the Action object's behavior:

       chdir
           If chdir is true (the default is False), SCons will change
           directories before executing the action. If the value of chdir is a
           string or a directory Node, SCons will change to the specified
           directory. Otherwise, if chdir evaluates true, SCons will change to
           the target file's directory.

           Note that SCons will not automatically modify its expansion of
           construction variables like $TARGET and $SOURCE when using the
           chdir parameter - that is, the expanded file names will still be
           relative to the top-level directory containing the SConstruct file,
           and consequently incorrect relative to the chdir directory.
           Builders created using chdir keyword argument, will need to use
           construction variable expansions like ${TARGET.file} and
           ${SOURCE.file} to use just the filename portion of the targets and
           source. Example:

               a = Action("build < ${SOURCE.file} > ${TARGET.file}", chdir=True)

       exitstatfunc
           If provided, must be a callable which accepts a single parameter,
           the exit status (or return value) from the specified action, and
           which returns an arbitrary or modified value. This can be used, for
           example, to specify that an Action object's return value should be
           ignored under special conditions and SCons should, therefore,
           consider that the action always succeeds. Example:

               def always_succeed(s):
                   # Always return 0, which indicates success.
                   return 0

               a = Action("build < ${SOURCE.file} > ${TARGET.file}",
                          exitstatfunc=always_succeed)

       batch_key
           If provided, indicates that the Action can create multiple target
           files by processing multiple independent source files
           simultaneously. (The canonical example is "batch compilation" of
           multiple object files by passing multiple source files to a single
           invocation of a compiler such as Microsoft's Visual C / C++
           compiler.) If the batch_key argument evaluates True and is not a
           callable object, the configured Action object will cause scons to
           collect all targets built with the Action object and configured
           with the same construction environment into single invocations of
           the Action object's command line or function. Command lines will
           typically want to use the $CHANGED_SOURCES construction variable
           (and possibly $CHANGED_TARGETS as well) to only pass to the command
           line those sources that have actually changed since their targets
           were built. Example:

               a = Action('build $CHANGED_SOURCES', batch_key=True)

           The batch_key argument may also be a callable function that returns
           a key that will be used to identify different "batches" of target
           files to be collected for batch building. A batch_key function must
           accept four parameters: action, env, target and source. The first
           parameter, action, is the active action object. The second
           parameter, env, is the construction environment configured for the
           target. The target and source parameters are the lists of targets
           and sources for the configured action.

           The returned key should typically be a tuple of values derived from
           the arguments, using any appropriate logic to decide how multiple
           invocations should be batched. For example, a batch_key function
           may decide to return the value of a specific construction variable
           from env which will cause scons to batch-build targets with
           matching values of that construction variable, or perhaps return
           the Python id() of the entire construction environment, in which
           case scons will batch-build all targets configured with the same
           construction environment. Returning None indicates that the
           particular target should not be part of any batched build, but
           instead will be built by a separate invocation of action's command
           or function. Example:

               def batch_key(action, env, target, source):
                   tdir = target[0].dir
                   if tdir.name == 'special':
                       # Don't batch-build any target
                       # in the special/ subdirectory.
                       return None
                   return (id(action), id(env), tdir)
               a = Action('build $CHANGED_SOURCES', batch_key=batch_key)

   Miscellaneous Action Functions
       SCons supplies Action functions that arrange for various common file
       and directory manipulations to be performed. These are similar in
       concept to "tasks" in the Ant build tool, although the implementation
       is slightly different. These functions do not actually perform the
       specified action at the time the function is called, but rather are
       factory functions which return an Action object that can be executed at
       the appropriate time.

       There are two natural ways that these Action Functions are intended to
       be used.

       First, if you need to perform the action at the time the SConscript
       file is being read, you can use the Execute global function:

           Execute(Touch('file'))

       Second, you can use these functions to supply Actions in a list for use
       by the env.Command method. This can allow you to perform more
       complicated sequences of file manipulation without relying on
       platform-specific external commands:

           env = Environment(TMPBUILD='/tmp/builddir')
           env.Command(
               target='foo.out',
               source='foo.in',
               action=[
                   Mkdir('$TMPBUILD'),
                   Copy('$TMPBUILD', '${SOURCE.dir}'),
                   "cd $TMPBUILD && make",
                   Delete('$TMPBUILD'),
               ],
           )

       Chmod(dest, mode)
           Returns an Action object that changes the permissions on the
           specified dest file or directory to the specified mode which can be
           octal or string, similar to the bash command. Examples:

               Execute(Chmod('file', 0o755))

               env.Command('foo.out', 'foo.in',
                           [Copy('$TARGET', '$SOURCE'),
                            Chmod('$TARGET', 0o755)])

               Execute(Chmod('file', "ugo+w"))

               env.Command('foo.out', 'foo.in',
                           [Copy('$TARGET', '$SOURCE'),
                            Chmod('$TARGET', "ugo+w")])

           The behavior of Chmod is limited on Windows, see the notes in the
           Python documentation for os.chmod, which is the underlying
           function.

       Copy(dest, src)
           Returns an Action object that will copy the src source file or
           directory to the dest destination file or directory. Examples:

               Execute(Copy('foo.output', 'foo.input'))

               env.Command('bar.out', 'bar.in', Copy('$TARGET', '$SOURCE'))

       Delete(entry, [must_exist])
           Returns an Action that deletes the specified entry, which may be a
           file or a directory tree. If a directory is specified, the entire
           directory tree will be removed. If the must_exist flag is set to a
           true value, then a Python error will be raised if the specified
           entry does not exist; the default is false, that is, the Action
           will silently do nothing if the entry does not exist. Examples:

               Execute(Delete('/tmp/buildroot'))

               env.Command(
                   'foo.out',
                   'foo.in',
                   action=[
                       Delete('${TARGET.dir}'),
                       MyBuildAction,
                   ],
               )

               Execute(Delete('file_that_must_exist', must_exist=True))

       Mkdir(name)
           Returns an Action that creates the directory name and all needed
           intermediate directories.  name may also be a list of directories
           to create. Examples:

               Execute(Mkdir('/tmp/outputdir'))

               env.Command(
                   'foo.out',
                   'foo.in',
                   action=[
                       Mkdir('/tmp/builddir'),
                       Copy('/tmp/builddir/foo.in', '$SOURCE'),
                       "cd /tmp/builddir && make",
                       Copy('$TARGET', '/tmp/builddir/foo.out'),
                   ],
               )

       Move(dest, src)
           Returns an Action that moves the specified src file or directory to
           the specified dest file or directory. Examples:

               Execute(Move('file.destination', 'file.source'))

               env.Command(
                   'output_file',
                   'input_file',
                   action=[MyBuildAction, Move('$TARGET', 'file_created_by_MyBuildAction')],
               )

       Touch(file)
           Returns an Action that updates the modification time on the
           specified file. Examples:

               Execute(Touch('file_to_be_touched'))

               env.Command('marker', 'input_file', action=[MyBuildAction, Touch('$TARGET')])

   Variable Substitution
       Before executing a command, scons performs variable substitution on the
       string that makes up the action part of the builder. Variables to be
       interpolated are indicated in the string with a leading $, to
       distinguish them from plain text which is not to be substituted. The
       name may be surrounded by curly braces (${}) to separate the name from
       surrounding characters if necessary. Curly braces are required when you
       use Python list subscripting/slicing notation on a variable to select
       one or more items from a list, or access a variable's special
       attributes, or use Python expression substitution.

       Besides regular construction variables, scons provides the following
       special variables for use in expanding commands:

       $CHANGED_SOURCES
           The file names of all sources of the build command that have
           changed since the target was last built.

       $CHANGED_TARGETS
           The file names of all targets that would be built from sources that
           have changed since the target was last built.

       $SOURCE
           The file name of the source of the build command, or the file name
           of the first source if multiple sources are being built.

       $SOURCES
           The file names of the sources of the build command.

       $TARGET
           The file name of the target being built, or the file name of the
           first target if multiple targets are being built.

       $TARGETS
           The file names of all targets being built.

       $UNCHANGED_SOURCES
           The file names of all sources of the build command that have not
           changed since the target was last built.

       $UNCHANGED_TARGETS
           The file names of all targets that would be built from sources that
           have not changed since the target was last built.

       These names are reserved and may not be assigned to or used as
       construction variables.

       For example, the following builder call:

           env = Environment(CC='cc')
           env.Command(
               target=['foo'],
               source=['foo.c', 'bar.c'],
               action='@echo $CC -c -o $TARGET $SOURCES'
           )

       would produce the following output:

           cc -c -o foo foo.c bar.c

       In the previous example, a string ${SOURCES[1]} would expand to: bar.c.

       A variable name may have the following modifiers appended within the
       enclosing curly braces to access properties of the interpolated string.
       These are known as special attributes.
           base -
               The base path of the file name,
               including the directory path
               but excluding any suffix.

           dir - The name of the directory in which the file exists.
           file -  The file name, minus any directory portion.
           filebase - Like file but minus its suffix.
           suffix - Just the file suffix.
           abspath - The absolute path name of the file.
           relpath - The path name of the file relative to the root SConstruct
           file's directory.
           posix -
               The path with directories separated by forward slashes
               (/).
               Sometimes necessary on Windows systems
               when a path references a file on other (POSIX) systems.

           windows -
               The path with directories separated by backslashes
               (\\).
               Sometimes necessary on POSIX-style systems
               when a path references a file on other (Windows) systems.
               win32 is a (deprecated) synonym for
               windows.

           srcpath -
               The directory and file name to the source file linked to this
           file through
               VariantDir().
               If this file isn't linked,
               it just returns the directory and filename unchanged.

           srcdir -
               The directory containing the source file linked to this file
           through
               VariantDir().
               If this file isn't linked,
               it just returns the directory part of the filename.

           rsrcpath -
               The directory and file name to the source file linked to this
           file through
               VariantDir().
               If the file does not exist locally but exists in a Repository,
               the path in the Repository is returned.
               If this file isn't linked, it just returns the
               directory and filename unchanged.

           rsrcdir -
               The Repository directory containing the source file linked to
           this file through
               VariantDir().
               If this file isn't linked,
               it just returns the directory part of the filename.


       For example, the specified target will expand as follows for the
       corresponding modifiers:

           $TARGET              => sub/dir/file.x
           ${TARGET.base}       => sub/dir/file
           ${TARGET.dir}        => sub/dir
           ${TARGET.file}       => file.x
           ${TARGET.filebase}   => file
           ${TARGET.suffix}     => .x
           ${TARGET.abspath}    => /top/dir/sub/dir/file.x
           ${TARGET.relpath}    => sub/dir/file.x

           $TARGET              => ../dir2/file.x
           ${TARGET.abspath}    => /top/dir2/file.x
           ${TARGET.relpath}    => ../dir2/file.x

           SConscript('src/SConscript', variant_dir='sub/dir')
           $SOURCE              => sub/dir/file.x
           ${SOURCE.srcpath}    => src/file.x
           ${SOURCE.srcdir}     => src

           Repository('/usr/repository')
           $SOURCE              => sub/dir/file.x
           ${SOURCE.rsrcpath}   => /usr/repository/src/file.x
           ${SOURCE.rsrcdir}    => /usr/repository/src

       Some modifiers can be combined, like ${TARGET.srcpath.base),
       ${TARGET.file.suffix}, etc.

       The curly brace notation may also be used to enclose a Python
       expression to be evaluated. See the section called "Python Code
       Substitution" below for a description.

       A variable name may also be a Python function associated with a
       construction variable in the environment. The function should accept
       four arguments:
           target - a list of target nodes
           source - a list of source nodes
           env - the construction environment
           for_signature -
               a Boolean value that specifies
               whether the function is being called
               for generating a build signature.


       SCons will insert whatever the called function returns into the
       expanded string:

           def foo(target, source, env, for_signature):
               return "bar"

           # Will expand $BAR to "bar baz"
           env=Environment(FOO=foo, BAR="$FOO baz")

       As a reminder, this evaluation happens when $BAR is actually used in a
       builder action. The value of env['BAR'] will be exactly as it was set:
       "$FOO baz".

       You can use this feature to pass arguments to a Python function by
       creating a callable class that stores one or more arguments in an
       object, and then uses them when the __call__() method is called. Note
       that in this case, the entire variable expansion must be enclosed by
       curly braces so that the arguments will be associated with the
       instantiation of the class:

           class foo:
               def __init__(self, arg):
                   self.arg = arg

               def __call__(self, target, source, env, for_signature):
                   return self.arg + " bar"

           # Will expand $BAR to "my argument bar baz"
           env=Environment(FOO=foo, BAR="${FOO('my argument')} baz")

       The special pseudo-variables $( and $) may be used to surround parts of
       a command line that may change without causing a rebuild--that is,
       which are not included in the signature of target files built with this
       command. All text between $( and $) will be removed from the command
       line before it is added to file signatures, and the $( and $) will be
       removed before the command is executed. For example, the command line:

           echo Last build occurred $( $TODAY $). > $TARGET

       would execute the command:

           echo Last build occurred $TODAY. > $TARGET

       but the command signature added to any target files would be:

           echo Last build occurred  . > $TARGET

   Python Code Substitution
       If a substitutable expression using the notation ${something} does not
       appear to match one of the other substitution patterns, it is evaluated
       as a Python expression. This uses Python's eval function, with the
       globals parameter set to the current environment's set of construction
       variables, and the result substituted in. So in the following case:

           env.Command(
               'foo.out', 'foo.in', "echo ${COND==1 and 'FOO' or 'BAR'} > $TARGET"
           )

       the command executed will be either

           echo FOO > foo.out

       or

           echo BAR > foo.out

       according to the current value of env['COND'] when the command is
       executed. The evaluation takes place when the target is being built,
       not when the SConscript is being read. So if env['COND'] is changed
       later in the SConscript, the final value will be used.

       Here's a more complete example. Note that all of COND, FOO, and BAR are
       construction variables, and their values are substituted into the final
       command.  FOO is a list, so its elements are interpolated separated by
       spaces.

           env=Environment()
           env['COND'] = 1
           env['FOO'] = ['foo1', 'foo2']
           env['BAR'] = 'barbar'
           env.Command(
               'foo.out', 'foo.in', "echo ${COND==1 and FOO or BAR} > $TARGET"
           )

       will execute:

           echo foo1 foo2 > foo.out

       In point of fact, Python expression evaluation is how the special
       attributes are substituted: they are simply attributes of the Python
       objects that represent $TARGET, $SOURCES, etc., which SCons passes to
       eval which returns the value.

       SCons uses the following rules when converting construction variables
       into command lines:

       string
           When the value is a string it is interpreted as a space delimited
           list of command line arguments.

       list
           When the value is a list it is interpreted as a list of command
           line arguments. Each element of the list is converted to a string.

       other
           Anything that is not a list or string is converted to a string and
           interpreted as a single command line argument.

       newline
           Newline characters (\n) delimit lines. The newline parsing is done
           after all other parsing, so it is not possible for arguments (e.g.
           file names) to contain embedded newline characters.

           Note
           Use of the Python eval function is considered to have security
           implications, since, depending on input sources, arbitrary
           unchecked strings of code can be executed by the Python
           interpreter. Although SCons makes use of it in a somewhat
           restricted context, you should be aware of this issue when using
           the ${python-expression-for-subst} form.

   Scanner Objects
       You can use the Scanner function to define objects to scan new file
       types for implicit dependencies. The Scanner function accepts the
       following arguments:

       function
           This can be either:

           o   a Python function that will process the Node (file) and return
               a list of File Nodes representing the implicit dependencies
               (file names) found in the contents.

           o   a dictionary that maps keys (typically the file suffix, but see
               below for more discussion) to other Scanners that should be
               called.

           If the argument is a Python function, the function must accept
           three required arguments and an optional fourth:
               node -
                   The internal SCons node representing the file.
                   Use str(node)
                   to fetch the name of the file, and
                   node.get_contents()
                   to fetch the contents of the file as bytes or
                   node.get_text_contents()
                   to fetch the contents as text.
                   Note that the file is
                   not
                   guaranteed to exist before the scanner is called,
                   so the scanner function should check that
                   if there's any chance that the scanned file
                   might not exist
                   (for example, if it's built from other files).

               env - The construction environment for the scan.
               path -
                   A tuple (or list)
                   of directories that can be searched
                   for files.
                   This will usually be the tuple returned by the
                  path_function
                  argument (see below).

               arg -
                   The argument supplied when the scanner was created, if any
                   (default None.


       name
           The name of the Scanner. This is mainly used to identify the
           Scanner internally. The default value is "NONE".

       argument
           An optional argument that, if specified, will be passed to the
           scanner function (described above) and the path function (specified
           below).

       skeys
           An optional list that can be used to determine which scanner should
           be used for a given Node. In the usual case of scanning for file
           names, this argument will be a list of suffixes for the different
           file types that this Scanner knows how to scan. If the argument is
           a string, then it will be expanded into a list by the current
           environment.

       path_function
           A Python function that takes four or five arguments: a construction
           environment, a Node for the directory containing the SConscript
           file in which the first target was defined, a list of target nodes,
           a list of source nodes, and an optional argument supplied when the
           scanner was created. The path_function returns a tuple of
           directories that can be searched for files to be returned by this
           Scanner object. (Note that the FindPathDirs function can be used to
           return a ready-made path_function for a given construction variable
           name, instead of having to write your own function from scratch.)

       node_class
           The class of Node that should be returned by this Scanner object.
           Any strings or other objects returned by the scanner function that
           are not of this class will be run through the function supplied by
           the node_factory argument.

       node_factory
           A Python function that will take a string or other object and turn
           it into the appropriate class of Node to be returned by this
           Scanner object.

       scan_check
           An optional Python function that takes two arguments, a Node (file)
           and a construction environment, and returns whether the Node
           should, in fact, be scanned for dependencies. This check can be
           used to eliminate unnecessary calls to the scanner function when,
           for example, the underlying file represented by a Node does not yet
           exist.

       recursive
           An optional flag that specifies whether this scanner should be
           re-invoked on the dependency files returned by the scanner. When
           this flag is not set, the Node subsystem will only invoke the
           scanner on the file being scanned, and not (for example) also on
           the files specified by the #include lines in the file being
           scanned.  recursive may be a callable function, in which case it
           will be called with a list of Nodes found and should return a list
           of Nodes that should be scanned recursively; this can be used to
           select a specific subset of Nodes for additional scanning.

       Note that scons has a global SourceFileScanner object that is used by
       the Object, SharedObject and StaticObject builders to decide which
       scanner should be used for different file extensions. You can use the
       SourceFileScanner.add_scanner() method to add your own Scanner object
       to the SCons infrastructure that builds target programs or libraries
       from a list of source files of different types:

           def xyz_scan(node, env, path):
               contents = node.get_text_contents()
               # Scan the contents and return the included files.

           XYZScanner = Scanner(xyz_scan)

           SourceFileScanner.add_scanner('.xyz', XYZScanner)

           env.Program('my_prog', ['file1.c', 'file2.f', 'file3.xyz'])

SYSTEM-SPECIFIC BEHAVIOR
       scons and its configuration files are very portable, due largely to its
       implementation in Python. There are, however, a few portability issues
       waiting to trap the unwary.

   .C file suffix
       scons handles the upper-case .C file suffix differently, depending on
       the capabilities of the underlying system. On a case-sensitive system
       such as Linux or UNIX, scons treats a file with a .C suffix as a C++
       source file. On a case-insensitive system such as Windows, scons treats
       a file with a .C suffix as a C source file.

   Fortran file suffixes
       scons handles upper-case Fortran file suffixes differently depending on
       the capabilities of the underlying system. On a case-sensitive system
       such as Linux or UNIX, scons treats a file with a .F as a Fortran
       source file that is to be first run through the standard C
       preprocessor, while the lower-case version is not. This matches the
       convention of gfortran, which may also be followed by other Fortran
       compilers. This also applies to other naming variants, .FOR, .FTN,
       .F90, .F95, .F03 and .F08; files suffixed with .FPP and .fpp are both
       run through the preprocessor, as indicated by the pp part of the name.
       On a case-insensitive system such as Windows, scons treats a file with
       a .F suffix as a Fortran source file that should not be run through the
       C preprocessor.

       Run through the C preprocessor here means that a different set of
       construction variables will be applied in constructed commands, for
       example $FORTRANPPCOM and $FORTRANPPCOMSTR instead of $FORTRANCOM and
       $FORTRANCOMSTR. See the Fortran-related construction variables for more
       details.

   Windows: Cygwin Tools and Cygwin Python vs. Windows Pythons
       Cygwin supplies a set of tools and utilities that let users work on a
       Windows system using a more POSIX-like environment. The Cygwin tools,
       including Cygwin Python, do this, in part, by sharing an ability to
       interpret UNIX-like path names. For example, the Cygwin tools will
       internally translate a Cygwin path name like /cygdrive/c/mydir to an
       equivalent Windows pathname of C:/mydir (equivalent to C:\mydir).

       Versions of Python that are built for native Windows execution, such as
       the python.org and ActiveState versions, do not have the Cygwin path
       name semantics. This means that using a native Windows version of
       Python to build compiled programs using Cygwin tools (such as gcc,
       bison and flex) may yield unpredictable results. "Mixing and matching"
       in this way can be made to work, but it requires careful attention to
       the use of path names in your SConscript files.

       In practice, users can sidestep the issue by adopting the following
       rules: When using gcc, use the Cygwin-supplied Python interpreter to
       run scons; when using Microsoft Visual C/C++ (or some other Windows
       compiler) use the python.org or Microsoft Store or ActiveState version
       of Python to run scons.

   Windows: scons.bat file
       On Windows systems, scons is executed via a wrapper scons.bat file.
       This has (at least) two ramifications:

       First, Windows command-line users that want to use variable assignment
       on the command line may have to put double quotes around the
       assignments:

           scons "FOO=BAR" "BAZ=BLEH"

       Second, the Cygwin shell does not recognize this file as being the same
       as an scons command issued at the command-line prompt. You can work
       around this either by executing scons.bat from the Cygwin command line,
       or by creating a wrapper shell script named scons.

   MinGW
       The MinGW bin directory must be in your PATH environment variable or
       the ['ENV']['PATH'] construction variable for scons to detect and use
       the MinGW tools. When running under the native Windows Python
       interpreter, scons will prefer the MinGW tools over the Cygwin tools,
       if they are both installed, regardless of the order of the bin
       directories in the PATH variable. If you have both MSVC and MinGW
       installed and you want to use MinGW instead of MSVC, then you must
       explicitly tell scons to use MinGW by passing tools=['mingw'] to the
       Environment function, because scons will prefer the MSVC tools over the
       MinGW tools.

ENVIRONMENT
       In general, scons is not controlled by environment variables set in the
       shell used to invoke it, leaving it up to the SConscript file author to
       import those if desired. However the following variables are imported
       by scons itself if set:

       SCONS_LIB_DIR
           Specifies the directory that contains the scons Python module
           directory. Normally scons can deduce this, but in some
           circumstances, such as working with a source release, it may be
           necessary to specify (for example,
           /home/aroach/scons-src-0.01/src/engine).

       SCONSFLAGS
           A string containing options that will be used by scons in addition
           to those passed on the command line. Can be used to reduce frequent
           retyping of common options. The contents of SCONSFLAGS are
           considered before any passed command line options, so the command
           line can be used to override SCONSFLAGS options if necessary.

       SCONS_CACHE_MSVC_CONFIG
           (Windows only). If set, save the shell environment variables
           generated when setting up the Microsoft Visual C++ compiler (and/or
           Build Tools) to a cache file, to give these settings, which are
           relatively expensive to generate, persistence across scons
           invocations. Use of this option is primarily intended to aid
           performance in tightly controlled Continuous Integration setups.

           If set to a True-like value ("1", "true" or "True") will cache to a
           file named .scons_msvc_cache in the user's home directory. If set
           to a pathname, will use that pathname for the cache.

           Note: use this cache with caution as it might be somewhat fragile:
           while each major toolset version (e.g. Visual Studio 2017 vs 2019)
           and architecture pair will get separate cache entries, if toolset
           updates cause a change to settings within a given release series,
           scons will not detect the change and will reuse old settings.
           Remove the cache file in case of problems with this.  scons will
           ignore failures reading or writing the file and will silently
           revert to non-cached behavior in such cases.

           Available since scons 3.1 (experimental).


ATTRIBUTES
       See attributes(7) for descriptions of the following attributes:


       +---------------+-----------------------+
       |ATTRIBUTE TYPE |   ATTRIBUTE VALUE     |
       +---------------+-----------------------+
       |Availability   | developer/build/scons |
       +---------------+-----------------------+
       |Stability      | Volatile              |
       +---------------+-----------------------+

SEE ALSO
               The SCons User Guide at
               https://scons.org/doc/production/HTML/scons-user.html

           The SCons Design Document (old)

               The SCons Cookbook at
               https://scons-cookbook.readthedocs.io
               for examples of how to solve various problems with SCons.


               SCons source code
               on GitHub[5]


               The SCons API Reference
               https://scons.org/doc/production/HTML/scons-api/index.html
               (for internal details)


AUTHORS
       Originally: Steven Knight knight@baldmt.com and Anthony Roach
       aroach@electriceyeball.com.

       Since 2010: The SCons Development Team scons-dev@scons.org.

AUTHOR
       The SCons Development Team

COPYRIGHT
       Copyright (C) 2001 - 2021 The SCons Foundation

NOTES
        1. LLVM specification
           https://clang.llvm.org/docs/JSONCompilationDatabase.html

        2. ninja package
           https://pypi.org/project/ninja/

        3. If no_progress is set via SetOption in an SConscript file (but not
           if set in a site_init.py file) there will still be an initial
           status message about reading SConscript files since SCons has to
           start reading them before it can see the SetOption.

        4. http://www.opensource.org/licenses/alphabetical
           http://www.opensource.org/licenses/alphabetical

        5. on GitHub
           https://github.com/SCons/scons


       Source code for open source software components in Oracle Solaris can
       be found at https://www.oracle.com/downloads/opensource/solaris-source-
       code-downloads.html.

       This software was built from source available at
       https://github.com/oracle/solaris-userland.  The original community
       source was downloaded from
       https://sourceforge.net/projects/scons/files/scons/4.2.0/scons-4.2.0.tar.gz/download.

       Further information about this software can be found on the open source
       community website at http://www.scons.org/.



SCons 4.2.0 Version 4.2.0
          <pubdate>Released Sat, 31 Jul 2021 18:12:46 -0700</pubdate>
                                                                      SCONS(1)