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Updated: Wednesday, February 10, 2021

ruby (1)


ruby - oriented scripting language


ruby  [--copyright]  [--version] [-SUacdlnpswvy] [-0[octal]] [-C direc-
tory] [-E external[:internal]]  [-F[pattern]]  [-I  directory]  [-K[c]]
[-T[level]]  [-W[level]]  [-e  command]  [-i[extension]]  [-r  library]
[-x[directory]]  [--{enable|disable}-FEATURE]  [--dump=target]  [--ver-
bose] [--] [program_file] [argument ...]


RUBY(1)                              UNIX                              RUBY(1)

       ruby - Interpreted object-oriented scripting language

       ruby  [--copyright]  [--version] [-SUacdlnpswvy] [-0[octal]] [-C direc-
       tory] [-E external[:internal]]  [-F[pattern]]  [-I  directory]  [-K[c]]
       [-T[level]]  [-W[level]]  [-e  command]  [-i[extension]]  [-r  library]
       [-x[directory]]  [--{enable|disable}-FEATURE]  [--dump=target]  [--ver-
       bose] [--] [program_file] [argument ...]

       Ruby  is  an  interpreted scripting language for quick and easy object-
       oriented programming.  It has many features to process text  files  and
       to  do system management tasks (like in Perl).  It is simple, straight-
       forward, and extensible.

       If you want a language for easy  object-oriented  programming,  or  you
       don't  like  the Perl ugliness, or you do like the concept of LISP, but
       don't like too many parentheses, Ruby might be your language of choice.

       Ruby's features are as follows:

              Ruby is an interpreted language, so you don't have to  recompile
              programs written in Ruby to execute them.

       Variables have no type (dynamic typing)
              Variables  in Ruby can contain data of any type.  You don't have
              to worry about variable typing.  Consequently, it has  a  weaker
              compile time check.

       No declaration needed
              You can use variables in your Ruby programs without any declara-
              tions.  Variable names  denote  their  scope  -  global,  class,
              instance, or local.

       Simple syntax
              Ruby has a simple syntax influenced slightly from Eiffel.

       No user-level memory management
              Ruby  has automatic memory management.  Objects no longer refer-
              enced from anywhere are automatically collected by  the  garbage
              collector built into the interpreter.

       Everything is an object
              Ruby  is a purely object-oriented language, and was so since its
              creation.  Even such basic data as integers are seen as objects.

       Class, inheritance, and methods
              Being an object-oriented language, Ruby naturally has basic fea-
              tures like classes, inheritance, and methods.

       Singleton methods
              Ruby has the ability to define methods for certain objects.  For
              example, you can define a press-button action for certain widget
              by defining a singleton method for the button.  Or, you can make
              up your own prototype based object system using singleton  meth-
              ods, if you want to.

       Mix-in by modules
              Ruby  intentionally does not have the multiple inheritance as it
              is a source of confusion.  Instead,  Ruby  has  the  ability  to
              share  implementations  across  the  inheritance  tree.  This is
              often called a `Mix-in'.

              Ruby has iterators for loop abstraction.

              In Ruby, you can objectify the procedure.

       Text processing and regular expressions
              Ruby has a bunch of text processing features like in Perl.

       M17N, character set independent
              Ruby supports  multilingualized  programming.  Easy  to  process
              texts written in many different natural languages and encoded in
              many different character encodings, without dependence  on  Uni-

              With  built-in  bignums,  you  can  for example calculate facto-

       Reflection and domain specific languages
              Class is also an instance of  the  Class  class.  Definition  of
              classes  and  methods  is  an expression just as 1+1 is. So your
              programs can even write and modify programs.  Thus you can write
              your  application  in  your  own  programming language on top of

       Exception handling
              As in Java(tm).

       Direct access to the OS
              Ruby can use most UNIX system calls, often used in  system  pro-

       Dynamic loading
              On  most  UNIX  systems, you can load object files into the Ruby
              interpreter on-the-fly.

       Rich libraries
              Libraries called "builtin libraries"  and  "standard  libraries"
              are  bundled  with  Ruby.  And you can obtain more libraries via
              the package management system called `RubyGems'.

              Moreover  there  are  thousands  of  Ruby  projects  on   GitHub

       Ruby  interpreter  accepts  following  command-line options (switches).
       They are quite similar to those of perl(1).

              Prints the copyright notice.

              Prints the version of Ruby interpreter.

              (The digit ``zero''.)   Specifies  the  input  record  separator
              ("$/")  as an octal number. If no digit is given, the null char-
              acter is taken as the separator.  Other switches may follow  the
              digits.   -00  turns Ruby into paragraph mode.  -0777 makes Ruby
              read whole file at once as a single string  since  there  is  no
              legal character with that value.

       -C directory

       -X directory
              Causes Ruby to switch to the directory.

       -E external[:internal]

       --encoding external[:internal]
              Specifies the default value(s) for external encodings and inter-
              nal encoding. Values should be separated with colon (:).

              You can omit the one for  internal  encodings,  then  the  value
              ("Encoding.default_internal") will be nil.


              Specify the default external or internal character encoding

       -F pattern
              Specifies input field separator ("$;").

       -I directory
              Used  to tell Ruby where to load the library scripts.  Directory
              path will be added to the load-path variable ("$:").

       -K kcode
              Specifies KANJI  (Japanese)  encoding.  The  default  value  for
              script   encodings   ("__ENCODING__")   and  external  encodings
              ("Encoding.default_external") will be the specified one.   kcode
              can be one of

       e      EUC-JP

       s      Windows-31J (CP932)

       u      UTF-8

       n      ASCII-8BIT (BINARY)

       -S     Makes  Ruby  use  the  PATH  environment  variable to search for
              script, unless its name begins with a slash.  This  is  used  to
              emulate  #!  on machines that don't support it, in the following

              #! /usr/ruby/2.3/bin/ruby
              # This line makes the next one a comment in Ruby \
                exec /usr/ruby/2.3/bin/ruby -S $0 $*

              Turns on taint checks at the specified level (default 1).

       -U     Sets  the  default  value  for   internal   encodings   ("Encod-
              ing.default_internal") to UTF-8.

              Turns  on  verbose  mode at the specified level without printing
              the version message at the beginning. The level can be;

       0      Verbose mode is "silence". It sets the "$VERBOSE" to nil.

       1      Verbose mode is "medium". It sets the "$VERBOSE" to false.

       2 (default)
              Verbose mode is "verbose". It sets the "$VERBOSE" to true.  -W 2
              is same as -w

       -a     Turns on auto-split mode when used with -n or -p.  In auto-split
              mode, Ruby executes
                $F = $_.split
              at beginning of each loop.

       -c     Causes Ruby to check the syntax of the script and  exit  without
              executing. If there are no syntax errors, Ruby will print ``Syn-
              tax OK'' to the standard output.


              Turns on debug mode.  "$DEBUG" will be set to true.

       -e command
              Specifies script from command-line while  telling  Ruby  not  to
              search the rest of the arguments for a script file name.


       --help Prints a summary of the options.

       -i extension
              Specifies  in-place-edit  mode.  The extension, if specified, is
              added to old file name to make a backup copy.  For example:

              % echo matz > /tmp/junk
              % cat /tmp/junk
              % ruby -p -i.bak -e '$_.upcase!' /tmp/junk
              % cat /tmp/junk
              % cat /tmp/junk.bak

       -l     (The lowercase letter ``ell''.)  Enables  automatic  line-ending
              processing,  which  means  to  firstly  set "$\" to the value of
              "$/", and secondly chops every line read using chop!.

       -n     Causes Ruby to assume the following  loop  around  your  script,
              which  makes  it  iterate over file name arguments somewhat like
              sed -n or awk.

              while gets

       -p     Acts mostly same as -n switch, but print the value  of  variable
              "$_" at the each end of the loop.  For example:

              % echo matz | ruby -p -e '$_.tr! "a-z", "A-Z"'

       -r library
              Causes  Ruby  to  load  the library using require.  It is useful
              when using -n or -p.

       -s     Enables some switch parsing for switches after script  name  but
              before  any  file name arguments (or before a --).  Any switches
              found there are removed from  ARGV  and  set  the  corresponding
              variable in the script.  For example:

              #! /usr/ruby/2.3/bin/ruby -s
              # prints "true" if invoked with `-xyz' switch.
              print "true\n" if $xyz

              On  some systems "$0" does not always contain the full pathname,
              so you need the -S switch to tell Ruby to search for the  script
              if  necessary  (to  handle  embedded spaces and such).  A better
              construct than "$*" would be ${1+"$@"}, but it does not work  if
              the script is being interpreted by csh(1).

       -v     Enables verbose mode.  Ruby will print its version at the begin-
              ning and set the variable  "$VERBOSE"  to  true.   Some  methods
              print  extra  messages if this variable is true.  If this switch
              is given, and no other switches are present,  Ruby  quits  after
              printing its version.

       -w     Enables  verbose  mode  without  printing version message at the
              beginning.  It sets the "$VERBOSE" variable to true.

              Tells Ruby that the script is embedded in  a  message.   Leading
              garbage  will be discarded until the first line that starts with
              ``#!''  and  contains  the  string,  ``ruby''.   Any  meaningful
              switches  on  that  line will be applied.  The end of the script
              must be specified with  either  EOF,  "^D"  ("control-D"),  "^Z"
              ("control-Z"),  or  the reserved word __END__.  If the directory
              name is specified, Ruby will switch  to  that  directory  before
              executing script.


              DO NOT USE.

              Turns on compiler debug mode.  Ruby will print a bunch of inter-
              nal state messages during compilation.  Only specify this switch
              you are going to debug the Ruby interpreter.


              Disables (or enables) the specified FEATURE .


              Disables (or enables) RubyGems libraries.  By default, Ruby will
              load the latest version of each installed gem. The Gem  constant
              is true if RubyGems is enabled, false if otherwise.


              Ignores  (or  considers)  the  RUBYOPT  environment variable. By
              default, Ruby considers the variable.


              Disables (or enables) all features.

              Dump some informations.

              Prints the specified target.  target can be one of;

              version description same as --version

       usage  brief usage message same as -h

       help   Show long help message same as --help

       syntax check of syntax same as -c --yydebug

              compiler debug mode, same as --yydebug

              Only specify this switch if you are  going  to  debug  the  Ruby


              AST nodes tree

              Only  specify  this  switch  if  you are going to debug the Ruby

       insns  disassembled instructions

              Only specify this switch if you are  going  to  debug  the  Ruby

              Enables  verbose  mode  without  printing version message at the
              beginning.  It sets the "$VERBOSE" variable to  true.   If  this
              switch  is  given, and no other switches are present, Ruby quits
              after printing its version.

              A colon-separated list of directories that are added  to  Ruby's
              library  load  path  ("$:").  Directories  from this environment
              variable are searched before the standard load path is searched.


              Additional Ruby options.

                RUBYOPT="-w -Ke"

              Note       that       RUBYOPT       can       contain       only
              -d,-E,-I,-K,-r,-T,-U,-v,-w,-W,  --debug,  --disable-FEATURE  and

              A colon-separated list of directories  that  Ruby  searches  for
              Ruby programs when the -S flag is specified.  This variable pre-
              cedes the PATH environment variable.

              The path to the system shell command.  This environment variable
              is  enabled  for  only mswin32, mingw32, and OS/2 platforms.  If
              this variable is not defined, Ruby refers to COMSPEC.

       PATH   Ruby refers to the PATH environment  variable  on  calling  Ker-

              And  Ruby depends on some RubyGems related environment variables
              unless RubyGems is disabled.  See the help of gem(1) as below.

              % gem help

       The Ruby garbage collector (GC) tracks objects  in  fixed-sized  slots,
       but  each  object  may have auxiliary memory allocations handled by the
       malloc family of C standard library calls ( malloc(3),  calloc(3),  and
       realloc(3))  In  this  documentatation,  the  "heap" refers to the Ruby
       object heap of fixed-sized slots, while "malloc"  refers  to  auxiliary
       allocations commonly referred to as the "process heap".  Thus there are
       at least two possible ways to trigger GC:

       1      Reaching the object limit.

       2      Reaching the malloc limit.

              In Ruby 2.1, the generational GC was introduced and  the  limits
              are  divided into young and old generations, providing two addi-
              tional ways to trigger a GC:

       3      Reaching the old object limit.

       4      Reaching the old malloc limit.

              There are currently 4 possible areas where the GC may  be  tuned
              by the the following 11 environment variables:

              Initial  allocation  slots.   Introduced  in  Ruby 2.1, default:

              Prepare at least this amount of slots after GC.   Allocate  this
              number  slots if there are not enough slots.  Introduced in Ruby
              2.1, default: 4096

              Increase allocation rate of heap slots by this  factor.   Intro-
              duced in Ruby 2.1, default: 1.8, minimum: 1.0 (no growth)

              Allocation  rate  is limited to this number of slots, preventing
              excessive allocation due to RUBY_GC_HEAP_GROWTH_FACTOR.   Intro-
              duced in Ruby 2.1, default: 0 (no limit)

              Perform  a full GC when the number of old objects is more than R
              * N, where R is this factor and N is the number of  old  objects
              after the last full GC.  Introduced in Ruby 2.1.1, default: 2.0

              The  initial  limit of young generation allocation from the mal-
              loc-family.  GC will start when this limit is reached.  Default:

              The  maximum  limit  of  young generation allocation from malloc
              before GC starts.   Prevents  excessive  malloc  growth  due  to
              RUBY_GC_MALLOC_LIMIT_GROWTH_FACTOR.   Introduced  in  Ruby  2.1,
              default: 32MB.

              Increases the limit of young generation malloc  calls,  reducing
              GC  frequency  but  increasing  malloc growth until RUBY_GC_MAL-
              LOC_LIMIT_MAX is reached.  Introduced in Ruby 2.1, default: 1.4,
              minimum: 1.0 (no growth)

              The  initial  limit  of old generation allocation from malloc, a
              full GC will start when this limit is  reached.   Introduced  in
              Ruby 2.1, default: 16MB

              The  maximum  limit  of  old  generation  allocation from malloc
              before a full GC starts.  Prevents excessive malloc  growth  due
              to  RUBY_GC_OLDMALLOC_LIMIT_GROWTH_FACTOR.   Introduced  in Ruby
              2.1, default: 128MB

              Increases the limit of old generation malloc allocation,  reduc-
              ing  full  GC  frequency  but  increasing  malloc  growth  until
              RUBY_GC_OLDMALLOC_LIMIT_MAX is reached.  Introduced in Ruby 2.1,
              default: 1.2, minimum: 1.0 (no growth)

       Stack  size environment variables are implementation-dependent and sub-
       ject to change with different versions of Ruby.  The VM stack  is  used
       for  pure-Ruby  code and managed by the virtual machine.  Machine stack
       is used by the operating system and its usage is dependent on C  exten-
       sions  as well as C compiler options.  Using lower values for these may
       allow  applications  to  keep  more  Fibers  or  Threads  running;  but
       increases  the  chance  of SystemStackError exceptions and segmentation
       faults (SIGSEGV).  These environment variables are available since Ruby
       2.0.0.  All values are specified in bytes.

              VM  stack size used at thread creation.  default: 131072 (32-bit
              CPU) or 262144 (64-bit)

              Machine stack size used at thread creation.  default: 524288  or

              VM stack size used at fiber creation.  default: 65536 or 131072

              Machine  stack  size used at fiber creation.  default: 262144 or

       See attributes(7) for descriptions of the following attributes:

       |Availability   | runtime/ruby-23  |
       |Stability      | Uncommitted      |
              The official web site.

              Comprehensive catalog of Ruby libraries.

       Security vulnerabilities should be reported  via  an  email  to  <secu-
       rity@ruby-lang.org>  Reported  problems will be published after they've
       been fixed.

       And you can report other bugs and feature requests via the  Ruby  Issue
       Tracking  System (https://bugs.ruby-lang.org/).  Do not report security
       vulnerabilities via the system because it publishes the vulnerabilities

       Ruby  is  designed  and  implemented  by  Yukihiro Matsumoto <matz@net-

       See  <https://bugs.ruby-lang.org/projects/ruby/wiki/Contributors>   for
       contributors to Ruby.

       The following files specify the installation locations for Ruby:

              Contains  the  Rubygems repository. Configure the GEM_HOME envi-
              ronment variable to point  to  /usr/ruby/2.3/lib/ruby/gems/2.3.0
              as the installation of Rubygems repository.

              Per user location for gems, when installing with the gem install
              option --user-install (gem install --user-install ...  ).   This
              path is automatically added to GEM_PATH.

              Per user location for gem executables.

              Contains   the   Ruby  executable  as well as other utility pro-
              grams, and Rubygems programs. These  programs  are  linked  from
              /usr/bin.   For  example:  /usr/ruby/2.3/bin/ruby is linked from
              /usr/bin/ruby23, and may be linked  from  /usr/bin/ruby  if  the
              package  mediator  "ruby"  is  version "2.3" (see pkg(1)).  Also
              contains executables for  any  installed  gems  that  have  them
              (i.e.: thin, rails, etc).

       This     software     was    built    from    source    available    at
       https://github.com/oracle/solaris-userland.   The  original   community
       source        was       downloaded       from        http://cache.ruby-

       Further information about this software can be found on the open source
       community website at http://www.ruby-lang.org/.

October 31, 2015                              Ruby Programmers Reference Guide