man pages section 1: User Commands

Exit Print View

Updated: July 2014

perlos2 (1)


perlos2 - Perl under OS/2, DOS, Win0.3*, Win0.95 and WinNT.


One can read this document in the following formats:

man perlos2
view perl perlos2
explorer perlos2.html
info perlos2

to list some (not all may be available simultaneously), or
it may be read as is: either as README.os2, or

To read the .INF version of documentation (very recommended)
outside of OS/2, one needs an IBM's reader (may be available
on IBM ftp sites (?)  (URL anyone?)) or shipped with PC DOS
7.0 and IBM's Visual Age C++ 3.5.

A copy of a Win* viewer is contained in the "Just add OS/2
Warp" package

in ?:\JUST_ADD\view.exe. This gives one an access to EMX's
.INF docs as well (text form is available in /emx/doc in
EMX's distribution).  There is also a different viewer named

Note that if you have lynx.exe or netscape.exe installed,
you can follow WWW links from this document in .INF format.
If you have EMX docs installed correctly, you can follow
library links (you need to have "view emxbook" working by
setting "EMXBOOK" environment variable as it is described in
EMX docs).


Perl Programmers Reference Guide                       PERLOS2(1)

     perlos2 - Perl under OS/2, DOS, Win0.3*, Win0.95 and WinNT.

     One can read this document in the following formats:

             man perlos2
             view perl perlos2
             explorer perlos2.html
             info perlos2

     to list some (not all may be available simultaneously), or
     it may be read as is: either as README.os2, or

     To read the .INF version of documentation (very recommended)
     outside of OS/2, one needs an IBM's reader (may be available
     on IBM ftp sites (?)  (URL anyone?)) or shipped with PC DOS
     7.0 and IBM's Visual Age C++ 3.5.

     A copy of a Win* viewer is contained in the "Just add OS/2
     Warp" package

     in ?:\JUST_ADD\view.exe. This gives one an access to EMX's
     .INF docs as well (text form is available in /emx/doc in
     EMX's distribution).  There is also a different viewer named

     Note that if you have lynx.exe or netscape.exe installed,
     you can follow WWW links from this document in .INF format.
     If you have EMX docs installed correctly, you can follow
     library links (you need to have "view emxbook" working by
     setting "EMXBOOK" environment variable as it is described in
     EMX docs).

     The target is to make OS/2 one of the best supported
     platform for using/building/developing Perl and Perl
     applications, as well as make Perl the best language to use
     under OS/2. The secondary target is to try to make this work
     under DOS and Win* as well (but not too hard).

     The current state is quite close to this target. Known

     o    Some *nix programs use fork() a lot; with the mostly
          useful flavors of perl for OS/2 (there are several
          built simultaneously) this is supported; but some
          flavors do not support this (e.g., when Perl is called

perl v5.12.5         Last change: 2012-11-03                    1

Perl Programmers Reference Guide                       PERLOS2(1)

          from inside REXX).  Using fork() after useing
          dynamically loading extensions would not work with very
          old versions of EMX.

     o    You need a separate perl executable perl__.exe (see
          perl__.exe) if you want to use PM code in your
          application (as Perl/Tk or OpenGL Perl modules do)
          without having a text-mode window present.

          While using the standard perl.exe from a text-mode
          window is possible too, I have seen cases when this
          causes degradation of the system stability.  Using
          perl__.exe avoids such a degradation.

     o    There is no simple way to access WPS objects. The only
          way I know is via "OS2::REXX" and "SOM" extensions (see
          OS2::REXX, Som).  However, we do not have access to
          convenience methods of Object-REXX. (Is it possible at
          all? I know of no Object-REXX API.)  The "SOM"
          extension (currently in alpha-text) may eventually
          remove this shortcoming; however, due to the fact that
          DII is not supported by the "SOM" module, using "SOM"
          is not as convenient as one would like it.

     Please keep this list up-to-date by informing me about other

  Other OSes
     Since OS/2 port of perl uses a remarkable EMX environment,
     it can run (and build extensions, and - possibly - be built
     itself) under any environment which can run EMX. The current
     list is DOS, DOS-inside-OS/2, Win0.3*, Win0.95 and WinNT.
     Out of many perl flavors, only one works, see "perl_.exe".

     Note that not all features of Perl are available under these
     environments. This depends on the features the extender -
     most probably RSX - decided to implement.

     Cf. Prerequisites.

     EMX   EMX runtime is required (may be substituted by RSX).
           Note that it is possible to make perl_.exe to run
           under DOS without any external support by binding
           emx.exe/rsx.exe to it, see emxbind. Note that under
           DOS for best results one should use RSX runtime, which
           has much more functions working (like "fork", "popen"
           and so on). In fact RSX is required if there is no
           VCPI present. Note the RSX requires DPMI.  Many
           implementations of DPMI are known to be very buggy,

perl v5.12.5         Last change: 2012-11-03                    2

Perl Programmers Reference Guide                       PERLOS2(1)

           Only the latest runtime is supported, currently "0.9d
           fix 03". Perl may run under earlier versions of EMX,
           but this is not tested.

           One can get different parts of EMX from, say


           The runtime component should have the name

           NOTE. When using emx.exe/rsx.exe, it is enough to have
           them on your path. One does not need to specify them
           explicitly (though this

             emx perl_.exe -de 0

           will work as well.)

     RSX   To run Perl on DPMI platforms one needs RSX runtime.
           This is needed under DOS-inside-OS/2, Win0.3*, Win0.95
           and WinNT (see "Other OSes"). RSX would not work with
           VCPI only, as EMX would, it requires DMPI.

           Having RSX and the latest sh.exe one gets a fully
           functional *nix-ish environment under DOS, say,
           "fork", "``" and pipe-"open" work. In fact, MakeMaker
           works (for static build), so one can have Perl
           development environment under DOS.

           One can get RSX from, say


           Contact the author on

           The latest sh.exe with DOS hooks is available in


           as or under similar names starting with
           "sh", "pdksh" etc.

     HPFS  Perl does not care about file systems, but the perl
           library contains many files with long names, so to
           install it intact one needs a file system which
           supports long file names.

           Note that if you do not plan to build the perl itself,
           it may be possible to fool EMX to truncate file names.

perl v5.12.5         Last change: 2012-11-03                    3

Perl Programmers Reference Guide                       PERLOS2(1)

           This is not supported, read EMX docs to see how to do

     pdksh To start external programs with complicated command
           lines (like with pipes in between, and/or quoting of
           arguments), Perl uses an external shell. With EMX port
           such shell should be named sh.exe, and located either
           in the wired-in-during-compile locations (usually
           F:/bin), or in configurable location (see

           For best results use EMX pdksh. The standard binary
           (5.2.14 or later) runs under DOS (with RSX) as well,


  Starting Perl programs under OS/2 (and DOS and...)
     Start your Perl program with arguments "arg1 arg2
     arg3" the same way as on any other platform, by

             perl arg1 arg2 arg3

     If you want to specify perl options "-my_opts" to the perl
     itself (as opposed to your program), use

             perl -my_opts arg1 arg2 arg3

     Alternately, if you use OS/2-ish shell, like CMD or 4os2,
     put the following at the start of your perl script:

             extproc perl -S -my_opts

     rename your program to foo.cmd, and start it by typing

             foo arg1 arg2 arg3

     Note that because of stupid OS/2 limitations the full path
     of the perl script is not available when you use "extproc",
     thus you are forced to use "-S" perl switch, and your script
     should be on the "PATH". As a plus side, if you know a full
     path to your script, you may still start it with

             perl ../../blah/foo.cmd arg1 arg2 arg3

     (note that the argument "-my_opts" is taken care of by the
     "extproc" line in your script, see ""extproc" on the first

     To understand what the above magic does, read perl docs
     about "-S" switch - see perlrun, and cmdref about "extproc":

perl v5.12.5         Last change: 2012-11-03                    4

Perl Programmers Reference Guide                       PERLOS2(1)

             view perl perlrun
             man perlrun
             view cmdref extproc
             help extproc

     or whatever method you prefer.

     There are also endless possibilities to use executable
     extensions of 4os2, associations of WPS and so on...
     However, if you use *nixish shell (like sh.exe supplied in
     the binary distribution), you need to follow the syntax
     specified in "Switches" in perlrun.

     Note that -S switch supports scripts with additional
     extensions .cmd, .btm, .bat, .pl as well.

  Starting OS/2 (and DOS) programs under Perl
     This is what system() (see "system" in perlfunc), "``" (see
     "I/O Operators" in perlop), and open pipe (see "open" in
     perlfunc) are for. (Avoid exec() (see "exec" in perlfunc)
     unless you know what you do).

     Note however that to use some of these operators you need to
     have a sh-syntax shell installed (see "Pdksh", "Frequently
     asked questions"), and perl should be able to find it (see

     The cases when the shell is used are:

     1.  One-argument system() (see "system" in perlfunc), exec()
         (see "exec" in perlfunc) with redirection or shell meta-

     2.  Pipe-open (see "open" in perlfunc) with the command
         which contains redirection or shell meta-characters;

     3.  Backticks "``" (see "I/O Operators" in perlop) with the
         command which contains redirection or shell meta-

     4.  If the executable called by
         system()/exec()/pipe-open()/"``" is a script with the
         "magic" "#!" line or "extproc" line which specifies

     5.  If the executable called by
         system()/exec()/pipe-open()/"``" is a script without
         "magic" line, and $ENV{EXECSHELL} is set to shell;

     6.  If the executable called by
         system()/exec()/pipe-open()/"``" is not found (is not
         this remark obsolete?);

perl v5.12.5         Last change: 2012-11-03                    5

Perl Programmers Reference Guide                       PERLOS2(1)

     7.  For globbing (see "glob" in perlfunc, "I/O Operators" in
         perlop) (obsolete? Perl uses builtin globbing

     For the sake of speed for a common case, in the above
     algorithms backslashes in the command name are not
     considered as shell metacharacters.

     Perl starts scripts which begin with cookies "extproc" or
     "#!" directly, without an intervention of shell.  Perl uses
     the same algorithm to find the executable as pdksh: if the
     path on "#!" line does not work, and contains "/", then the
     directory part of the executable is ignored, and the
     executable is searched in . and on "PATH".  To find
     arguments for these scripts Perl uses a different algorithm
     than pdksh: up to 3 arguments are recognized, and trailing
     whitespace is stripped.

     If a script does not contain such a cooky, then to avoid
     calling sh.exe, Perl uses the same algorithm as pdksh: if
     $ENV{EXECSHELL} is set, the script is given as the first
     argument to this command, if not set, then "$ENV{COMSPEC}
     /c" is used (or a hardwired guess if $ENV{COMSPEC} is not

     When starting scripts directly, Perl uses exactly the same
     algorithm as for the search of script given by -S command-
     line option: it will look in the current directory, then on
     components of $ENV{PATH} using the following order of
     appended extensions: no extension, .cmd, .btm, .bat, .pl.

     Note that Perl will start to look for scripts only if OS/2
     cannot start the specified application, thus "system 'blah'"
     will not look for a script if there is an executable file
     blah.exe anywhere on "PATH".  In other words, "PATH" is
     essentially searched twice: once by the OS for an
     executable, then by Perl for scripts.

     Note also that executable files on OS/2 can have an
     arbitrary extension, but .exe will be automatically appended
     if no dot is present in the name.  The workaround is as
     simple as that:  since blah. and blah denote the same file
     (at list on FAT and HPFS file systems), to start an
     executable residing in file n:/bin/blah (no extension) give
     an argument "n:/bin/blah." (dot appended) to system().

     Perl will start PM programs from VIO (=text-mode) Perl
     process in a separate PM session; the opposite is not true:
     when you start a non-PM program from a PM Perl process, Perl
     would not run it in a separate session.  If a separate
     session is desired, either ensure that shell will be used,
     as in "system 'cmd /c myprog'", or start it using optional

perl v5.12.5         Last change: 2012-11-03                    6

Perl Programmers Reference Guide                       PERLOS2(1)

     arguments to system() documented in "OS2::Process" module.
     This is considered to be a feature.

Frequently asked questions
  "It does not work"
     Perl binary distributions come with a testperl.cmd script
     which tries to detect common problems with misconfigured
     installations.  There is a pretty large chance it will
     discover which step of the installation you managed to goof.

  I cannot run external programs
     o   Did you run your programs with "-w" switch? See "2 (and
         DOS) programs under Perl" in Starting OS.

     o   Do you try to run internal shell commands, like "`copy a
         b`" (internal for cmd.exe), or "`glob a*b`" (internal
         for ksh)? You need to specify your shell explicitly,
         like "`cmd /c copy a b`", since Perl cannot deduce which
         commands are internal to your shell.

  I cannot embed perl into my program, or use perl.dll from my
     Is your program EMX-compiled with "-Zmt -Zcrtdll"?
         Well, nowadays Perl DLL should be usable from a
         differently compiled program too...  If you can run Perl
         code from REXX scripts (see OS2::REXX), then there are
         some other aspect of interaction which are overlooked by
         the current hackish code to support differently-compiled
         principal programs.

         If everything else fails, you need to build a stand-
         alone DLL for perl. Contact me, I did it once. Sockets
         would not work, as a lot of other stuff.

     Did you use ExtUtils::Embed?
         Some time ago I had reports it does not work.  Nowadays
         it is checked in the Perl test suite, so grep ./t
         subdirectory of the build tree (as well as *.t files in
         the ./lib subdirectory) to find how it should be done

  "``" and pipe-"open" do not work under DOS.
     This may a variant of just "I cannot run external programs",
     or a deeper problem. Basically: you need RSX (see
     "Prerequisites") for these commands to work, and you may
     need a port of sh.exe which understands command arguments.
     One of such ports is listed in "Prerequisites" under RSX. Do
     not forget to set variable "PERL_SH_DIR" as well.

     DPMI is required for RSX.

perl v5.12.5         Last change: 2012-11-03                    7

Perl Programmers Reference Guide                       PERLOS2(1)

  Cannot start "find.exe "pattern" file"
     The whole idea of the "standard C API to start applications"
     is that the forms "foo" and "foo" of program arguments are
     completely interchangable.  find breaks this paradigm;

       find "pattern" file
       find pattern file

     are not equivalent; find cannot be started directly using
     the above API.  One needs a way to surround the doublequotes
     in some other quoting construction, necessarily having an
     extra non-Unixish shell in between.

     Use one of

       system 'cmd', '/c', 'find "pattern" file';
       `cmd /c 'find "pattern" file'`

     This would start find.exe via cmd.exe via "sh.exe" via
     "perl.exe", but this is a price to pay if you want to use
     non-conforming program.

  Automatic binary installation
     The most convenient way of installing a binary distribution
     of perl is via perl installer install.exe. Just follow the
     instructions, and 99% of the installation blues would go

     Note however, that you need to have unzip.exe on your path,
     and EMX environment running. The latter means that if you
     just installed EMX, and made all the needed changes to
     Config.sys, you may need to reboot in between. Check EMX
     runtime by running


     Binary installer also creates a folder on your desktop with
     some useful objects.  If you need to change some aspects of
     the work of the binary installer, feel free to edit the file
     Perl.pkg.  This may be useful e.g., if you need to run the
     installer many times and do not want to make many
     interactive changes in the GUI.

     Things not taken care of by automatic binary installation:

     "PERL_BADLANG" may be needed if you change your codepage
                    after perl installation, and the new value is
                    not supported by EMX. See "PERL_BADLANG".


perl v5.12.5         Last change: 2012-11-03                    8

Perl Programmers Reference Guide                       PERLOS2(1)      This file resides somewhere deep in the
                    location you installed your perl library,
                    find it out by

                      perl -MConfig -le "print $INC{''}"

                    While most important values in this file are
                    updated by the binary installer, some of them
                    may need to be hand-edited. I know no such
                    data, please keep me informed if you find
                    one.  Moreover, manual changes to the
                    installed version may need to be accompanied
                    by an edit of this file.

     NOTE. Because of a typo the binary installer of 5.00305
     would install a variable "PERL_SHPATH" into Config.sys.
     Please remove this variable and put "PERL_SH_DIR" instead.

  Manual binary installation
     As of version 5.00305, OS/2 perl binary distribution comes
     split into 11 components. Unfortunately, to enable
     configurable binary installation, the file paths in the zip
     files are not absolute, but relative to some directory.

     Note that the extraction with the stored paths is still
     necessary (default with unzip, specify "-d" to pkunzip).
     However, you need to know where to extract the files. You
     need also to manually change entries in Config.sys to
     reflect where did you put the files. Note that if you have
     some primitive unzipper (like "pkunzip"), you may get a lot
     of warnings/errors during unzipping. Upgrade to "(w)unzip".

     Below is the sample of what to do to reproduce the
     configuration on my machine.  In VIEW.EXE you can press
     "Ctrl-Insert" now, and cut-and-paste from the resulting file
     - created in the directory you started VIEW.EXE from.

     For each component, we mention environment variables related
     to each installation directory.  Either choose directories
     to match your values of the variables, or create/append-to
     variables to take into account the directories.

     Perl VIO and PM executables (dynamically linked)
          unzip *.exe *.ico -d f:/emx.add/bin
          unzip *.dll -d f:/emx.add/dll

        (have the directories with "*.exe" on PATH, and "*.dll"
        on LIBPATH);

     Perl_ VIO executable (statically linked)
          unzip -d f:/emx.add/bin

perl v5.12.5         Last change: 2012-11-03                    9

Perl Programmers Reference Guide                       PERLOS2(1)

        (have the directory on PATH);

     Executables for Perl utilities
          unzip -d f:/emx.add/bin

        (have the directory on PATH);

     Main Perl library
          unzip -d f:/perllib/lib

        If this directory is exactly the same as the prefix which
        was compiled into perl.exe, you do not need to change
        anything. However, for perl to find the library if you
        use a different path, you need to "set PERLLIB_PREFIX" in
        Config.sys, see "PERLLIB_PREFIX".

     Additional Perl modules
          unzip -d f:/perllib/lib/site_perl/5.12.5/

        Same remark as above applies.  Additionally, if this
        directory is not one of directories on @INC (and @INC is
        influenced by "PERLLIB_PREFIX"), you need to put this
        directory and subdirectory ./os2 in "PERLLIB" or
        "PERL5LIB" variable. Do not use "PERL5LIB" unless you
        have it set already. See "ENVIRONMENT" in perl.

        [Check whether this extraction directory is still
        applicable with the new directory structure layout!]

     Tools to compile Perl modules
          unzip -d f:/perllib/lib

        Same remark as for

     Manpages for Perl and utilities
          unzip -d f:/perllib/man

        This directory should better be on "MANPATH". You need to
        have a working man to access these files.

     Manpages for Perl modules
          unzip -d f:/perllib/man

        This directory should better be on "MANPATH". You need to
        have a working man to access these files.

     Source for Perl documentation
          unzip -d f:/perllib/lib

        This is used by the "perldoc" program (see perldoc), and
        may be used to generate HTML documentation usable by WWW
        browsers, and documentation in zillions of other formats:

perl v5.12.5         Last change: 2012-11-03                   10

Perl Programmers Reference Guide                       PERLOS2(1)

        "info", "LaTeX", "Acrobat", "FrameMaker" and so on.  [Use
        programs such as pod2latex etc.]

     Perl manual in .INF format
          unzip -d d:/os2/book

        This directory should better be on "BOOKSHELF".

          unzip -d f:/bin

        This is used by perl to run external commands which
        explicitly require shell, like the commands using
        redirection and shell metacharacters. It is also used
        instead of explicit /bin/sh.

        Set "PERL_SH_DIR" (see "PERL_SH_DIR") if you move sh.exe
        from the above location.

        Note. It may be possible to use some other sh-compatible
        shell (untested).

     After you installed the components you needed and updated
     the Config.sys correspondingly, you need to hand-edit This file resides somewhere deep in the location
     you installed your perl library, find it out by

       perl -MConfig -le "print $INC{''}"

     You need to correct all the entries which look like file
     paths (they currently start with "f:/").

     The automatic and manual perl installation leave precompiled
     paths inside perl executables. While these paths are
     overwriteable (see "PERLLIB_PREFIX", "PERL_SH_DIR"), some
     people may prefer binary editing of paths inside the

Accessing documentation
     Depending on how you built/installed perl you may have
     (otherwise identical) Perl documentation in the following

  OS/2 .INF file
     Most probably the most convenient form. Under OS/2 view it

       view perl
       view perl perlfunc
       view perl less
       view perl ExtUtils::MakeMaker

perl v5.12.5         Last change: 2012-11-03                   11

Perl Programmers Reference Guide                       PERLOS2(1)

     (currently the last two may hit a wrong location, but this
     may improve soon). Under Win* see "SYNOPSIS".

     If you want to build the docs yourself, and have OS/2
     toolkit, run

             pod2ipf > perl.ipf

     in /perllib/lib/pod directory, then

             ipfc /inf perl.ipf

     (Expect a lot of errors during the both steps.) Now move it
     on your BOOKSHELF path.

  Plain text
     If you have perl documentation in the source form, perl
     utilities installed, and GNU groff installed, you may use

             perldoc perlfunc
             perldoc less
             perldoc ExtUtils::MakeMaker

     to access the perl documentation in the text form (note that
     you may get better results using perl manpages).

     Alternately, try running pod2text on .pod files.

     If you have man installed on your system, and you installed
     perl manpages, use something like this:

             man perlfunc
             man 3 less
             man ExtUtils.MakeMaker

     to access documentation for different components of Perl.
     Start with

             man perl

     Note that dot (.) is used as a package separator for
     documentation for packages, and as usual, sometimes you need
     to give the section - 3 above - to avoid shadowing by the
     less(1) manpage.

     Make sure that the directory above the directory with
     manpages is on our "MANPATH", like this

       set MANPATH=c:/man;f:/perllib/man

perl v5.12.5         Last change: 2012-11-03                   12

Perl Programmers Reference Guide                       PERLOS2(1)

     for Perl manpages in "f:/perllib/man/man1/" etc.

     If you have some WWW browser available, installed the Perl
     documentation in the source form, and Perl utilities, you
     can build HTML docs. Cd to directory with .pod files, and do
     like this

             cd f:/perllib/lib/pod

     After this you can direct your browser the file perl.html in
     this directory, and go ahead with reading docs, like this:

             explore file:///f:/perllib/lib/pod/perl.html

     Alternatively you may be able to get these docs prebuilt
     from CPAN.

  GNU "info" files
     Users of Emacs would appreciate it very much, especially
     with "CPerl" mode loaded. You need to get latest "pod2texi"
     from "CPAN", or, alternately, the prebuilt info pages.

  PDF files
     for "Acrobat" are available on CPAN (may be for slightly
     older version of perl).

  "LaTeX" docs
     can be constructed using "pod2latex".

     Here we discuss how to build Perl under OS/2.

  The short story
     Assume that you are a seasoned porter, so are sure that all
     the necessary tools are already present on your system, and
     you know how to get the Perl source distribution.  Untar it,
     change to the extract directory, and

       gnupatch -p0 < os2\diff.configure
       sh Configure -des -D prefix=f:/perllib
       make test
       make install
       make aout_test
       make aout_install

     This puts the executables in f:/perllib/bin.  Manually move
     them to the "PATH", manually move the built perl*.dll to
     "LIBPATH" (here for Perl DLL * is a not-very-meaningful hex
     checksum), and run

perl v5.12.5         Last change: 2012-11-03                   13

Perl Programmers Reference Guide                       PERLOS2(1)

       make installcmd INSTALLCMDDIR=d:/ir/on/path

     Assuming that the "man"-files were put on an appropriate
     location, this completes the installation of minimal Perl
     system.  (The binary distribution contains also a lot of
     additional modules, and the documentation in INF format.)

     What follows is a detailed guide through these steps.

     You need to have the latest EMX development environment, the
     full GNU tool suite (gawk renamed to awk, and GNU find.exe
     earlier on path than the OS/2 find.exe, same with sort.exe,
     to check use

       find --version
       sort --version

     ). You need the latest version of pdksh installed as sh.exe.

     Check that you have BSD libraries and headers installed, and
     - optionally - Berkeley DB headers and libraries, and crypt.

     Possible locations to get the files:

     It is reported that the following archives contain enough
     utils to build perl:,,,,,,,, and (or a
     later version).  Note that all these utilities are known to
     be available from LEO:

     Note also that the db.lib and db.a from the EMX distribution
     are not suitable for multi-threaded compile (even single-
     threaded flavor of Perl uses multi-threaded C RTL, for
     compatibility with XFree86-OS/2). Get a corrected one from

     If you have exactly the same version of Perl installed
     already, make sure that no copies or perl are currently
     running.  Later steps of the build may fail since an older
     version of perl.dll loaded into memory may be found.
     Running "make test" becomes meaningless, since the test are
     checking a previous build of perl (this situation is

perl v5.12.5         Last change: 2012-11-03                   14

Perl Programmers Reference Guide                       PERLOS2(1)

     detected and reported by lib/os2_base.t test).  Do not
     forget to unset "PERL_EMXLOAD_SEC" in environment.

     Also make sure that you have /tmp directory on the current
     drive, and . directory in your "LIBPATH". One may try to
     correct the latter condition by

       set BEGINLIBPATH .\.

     if you use something like CMD.EXE or latest versions of
     4os2.exe.  (Setting BEGINLIBPATH to just "." is ignored by
     the OS/2 kernel.)

     Make sure your gcc is good for "-Zomf" linking: run
     "omflibs" script in /emx/lib directory.

     Check that you have link386 installed. It comes standard
     with OS/2, but may be not installed due to customization. If


     shows you do not have it, do Selective install, and choose
     "Link object modules" in Optional system utilities/More. If
     you get into link386 prompts, press "Ctrl-C" to exit.

  Getting perl source
     You need to fetch the latest perl source (including
     developers releases). With some probability it is located in

     If not, you may need to dig in the indices to find it in the
     directory of the current maintainer.

     Quick cycle of developers release may break the OS/2 build
     time to time, looking into

     may indicate the latest release which was publicly released
     by the maintainer. Note that the release may include some
     additional patches to apply to the current source of perl.

     Extract it like this

       tar vzxf perl5.00409.tar.gz

     You may see a message about errors while extracting
     Configure. This is because there is a conflict with a
     similarly-named file configure.

perl v5.12.5         Last change: 2012-11-03                   15

Perl Programmers Reference Guide                       PERLOS2(1)

     Change to the directory of extraction.

  Application of the patches
     You need to apply the patches in ./os2/diff.* like this:

       gnupatch -p0 < os2\diff.configure

     You may also need to apply the patches supplied with the
     binary distribution of perl.  It also makes sense to look on
     the perl5-porters mailing list for the latest OS/2-related
     patches (see
     Such patches usually contain strings "/os2/" and "patch", so
     it makes sense looking for these strings.

     You may look into the file ./hints/ and correct
     anything wrong you find there. I do not expect it is needed

       sh Configure -des -D prefix=f:/perllib

     "prefix" means: where to install the resulting perl library.
     Giving correct prefix you may avoid the need to specify

     Ignore the message about missing "ln", and about "-c" option
     to tr. The latter is most probably already fixed, if you see
     it and can trace where the latter spurious warning comes
     from, please inform me.



     At some moment the built may die, reporting a version
     mismatch or unable to run perl.  This means that you do not
     have . in your LIBPATH, so perl.exe cannot find the needed
     perl67B2.dll (treat these hex digits as line noise).  After
     this is fixed the build should finish without a lot of fuss.

     Now run

       make test

     All tests should succeed (with some of them skipped).  If
     you have the same version of Perl installed, it is crucial
     that you have "." early in your LIBPATH (or in
     BEGINLIBPATH), otherwise your tests will most probably test

perl v5.12.5         Last change: 2012-11-03                   16

Perl Programmers Reference Guide                       PERLOS2(1)

     the wrong version of Perl.

     Some tests may generate extra messages similar to

     A lot of "bad free"
         in database tests related to Berkeley DB. This should be
         fixed already.  If it persists, you may disable this
         warnings, see "PERL_BADFREE".

     Process terminated by SIGTERM/SIGINT
         This is a standard message issued by OS/2 applications.
         *nix applications die in silence. It is considered to be
         a feature. One can easily disable this by appropriate

         However the test engine bleeds these message to screen
         in unexpected moments. Two messages of this kind should
         be present during testing.

     To get finer test reports, call

       perl t/harness

     The report with io/pipe.t failing may look like this:

       Failed Test  Status Wstat Total Fail  Failed  List of failed
       io/pipe.t                    12    1   8.33%  9
       7 tests skipped, plus 56 subtests skipped.
       Failed 1/195 test scripts, 99.49% okay. 1/6542 subtests failed, 99.98% okay.

     The reasons for most important skipped tests are:

             18  Checks "atime" and "mtime" of "stat()" -
                 unfortunately, HPFS provides only 2sec time
                 granularity (for compatibility with FAT?).

             25  Checks "truncate()" on a filehandle just opened
                 for write - I do not know why this should or
                 should not work.

             Checks "stat()". Tests:

             4   Checks "atime" and "mtime" of "stat()" -
                 unfortunately, HPFS provides only 2sec time
                 granularity (for compatibility with FAT?).

  Installing the built perl
     If you haven't yet moved "perl*.dll" onto LIBPATH, do it

perl v5.12.5         Last change: 2012-11-03                   17

Perl Programmers Reference Guide                       PERLOS2(1)


       make install

     It would put the generated files into needed locations.
     Manually put perl.exe, perl__.exe and perl___.exe to a
     location on your PATH, perl.dll to a location on your


       make installcmd INSTALLCMDDIR=d:/ir/on/path

     to convert perl utilities to .cmd files and put them on
     PATH. You need to put .EXE-utilities on path manually. They
     are installed in "$prefix/bin", here $prefix is what you
     gave to Configure, see Making.

     If you use "man", either move the installed */man/
     directories to your "MANPATH", or modify "MANPATH" to match
     the location.  (One could have avoided this by providing a
     correct "manpath" option to ./Configure, or editing
     ./ between configuring and making steps.)

  "a.out"-style build
     Proceed as above, but make perl_.exe (see "perl_.exe") by

       make perl_

     test and install by

       make aout_test
       make aout_install

     Manually put perl_.exe to a location on your PATH.

     Note. The build process for "perl_" does not know about all
     the dependencies, so you should make sure that anything is
     up-to-date, say, by doing

       make perl_dll


Building a binary distribution
     [This section provides a short overview only...]

     Building should proceed differently depending on whether the
     version of perl you install is already present and used on
     your system, or is a new version not yet used.  The
     description below assumes that the version is new, so
     installing its DLLs and .pm files will not disrupt the

perl v5.12.5         Last change: 2012-11-03                   18

Perl Programmers Reference Guide                       PERLOS2(1)

     operation of your system even if some intermediate steps are
     not yet fully working.

     The other cases require a little bit more convoluted
     procedures.  Below I suppose that the current version of
     Perl is 5.8.2, so the executables are named accordingly.

     1.  Fully build and test the Perl distribution.  Make sure
         that no tests are failing with "test" and "aout_test"
         targets; fix the bugs in Perl and the Perl test suite
         detected by these tests.  Make sure that "all_test" make
         target runs as clean as possible.  Check that
         "os2/perlrexx.cmd" runs fine.

     2.  Fully install Perl, including "installcmd" target.  Copy
         the generated DLLs to "LIBPATH"; copy the numbered Perl
         executables (as in perl5.8.2.exe) to "PATH"; copy
         "perl_.exe" to "PATH" as "perl_5.8.2.exe".  Think
         whether you need backward-compatibility DLLs.  In most
         cases you do not need to install them yet; but sometime
         this may simplify the following steps.

     3.  Make sure that "" can download files from CPAN.
         If not, you may need to manually install "Net::FTP".

     4.  Install the bundle "Bundle::OS2_default"

           perl5.8.2 -MCPAN -e "install Bundle::OS2_default" < nul |& tee 00cpan_i_1

         This may take a couple of hours on 1GHz processor (when
         run the first time).  And this should not be necessarily
         a smooth procedure.  Some modules may not specify
         required dependencies, so one may need to repeat this
         procedure several times until the results stabilize.

           perl5.8.2 -MCPAN -e "install Bundle::OS2_default" < nul |& tee 00cpan_i_2
           perl5.8.2 -MCPAN -e "install Bundle::OS2_default" < nul |& tee 00cpan_i_3

         Even after they stabilize, some tests may fail.

         Fix as many discovered bugs as possible.  Document all
         the bugs which are not fixed, and all the failures with
         unknown reasons.  Inspect the produced logs 00cpan_i_1
         to find suspiciously skipped tests, and other fishy

         Keep in mind that installation of some modules may fail
         too: for example, the DLLs to update may be already
         loaded by  Inspect the "install" logs (in the
         example above 00cpan_i_1 etc) for errors, and install
         things manually, as in

perl v5.12.5         Last change: 2012-11-03                   19

Perl Programmers Reference Guide                       PERLOS2(1)

           cd $CPANHOME/.cpan/build/Digest-MD5-2.31
           make install

         Some distributions may fail some tests, but you may want
         to install them anyway (as above, or via "force install"
         command of "" shell-mode).

         Since this procedure may take quite a long time to
         complete, it makes sense to "freeze" your CPAN
         configuration by disabling periodic updates of the local
         copy of CPAN index: set "index_expire" to some big value
         (I use 365), then save the settings

           CPAN> o conf index_expire 365
           CPAN> o conf commit

         Reset back to the default value 1 when you are finished.

     5.  When satisfied with the results, rerun the "installcmd"
         target.  Now you can copy "perl5.8.2.exe" to "perl.exe",
         and install the other OMF-build executables:
         "perl__.exe" etc.  They are ready to be used.

     6.  Change to the "./pod" directory of the build tree,
         download the Perl logo CamelGrayBig.BMP, and run

           ( perl2ipf > perl.ipf ) |& tee 00ipf
           ipfc /INF perl.ipf |& tee 00inf

         This produces the Perl docs online book "perl.INF".
         Install in on "BOOKSHELF" path.

     7.  Now is the time to build statically linked executable
         perl_.exe which includes newly-installed via
         "Bundle::OS2_default" modules.  Doing testing via
         "" is going to be painfully slow, since it
         statically links a new executable per XS extension.

         Here is a possible workaround: create a toplevel
         Makefile.PL in $CPANHOME/.cpan/build/ with contents
         being (compare with "Making executables with a custom
         collection of statically loaded extensions")

           use ExtUtils::MakeMaker;
           WriteMakefile NAME => 'dummy';

         execute this as

           perl_5.8.2.exe Makefile.PL <nul |& tee 00aout_c1
           make -k all test <nul |& 00aout_t1

         Again, this procedure should not be absolutely smooth.

perl v5.12.5         Last change: 2012-11-03                   20

Perl Programmers Reference Guide                       PERLOS2(1)

         Some "Makefile.PL"'s in subdirectories may be buggy, and
         would not run as "child" scripts.  The interdependency
         of modules can strike you; however, since non-XS modules
         are already installed, the prerequisites of most modules
         have a very good chance to be present.

         If you discover some glitches, move directories of
         problematic modules to a different location; if these
         modules are non-XS modules, you may just ignore them -
         they are already installed; the remaining, XS, modules
         you need to install manually one by one.

         After each such removal you need to rerun the
         "Makefile.PL"/"make" process; usually this procedure
         converges soon.  (But be sure to convert all the
         necessary external C libraries from .lib format to .a
         format: run one of

           emxaout foo.lib
           emximp -o foo.a foo.lib

         whichever is appropriate.)  Also, make sure that the
         DLLs for external libraries are usable with with
         executables compiled without "-Zmtd" options.

         When you are sure that only a few subdirectories lead to
         failures, you may want to add "-j4" option to "make" to
         speed up skipping subdirectories with already finished

         When you are satisfied with the results of tests,
         install the build C libraries for extensions:

           make install |& tee 00aout_i

         Now you can rename the file ./perl.exe generated during
         the last phase to perl_5.8.2.exe; place it on "PATH"; if
         there is an inter-dependency between some XS modules,
         you may need to repeat the "test"/"install" loop with
         this new executable and some excluded modules - until
         the procedure converges.

         Now you have all the necessary .a libraries for these
         Perl modules in the places where Perl builder can find
         it.  Use the perl builder: change to an empty directory,
         create a "dummy" Makefile.PL again, and run

           perl_5.8.2.exe Makefile.PL |& tee 00c
           make perl                  |& tee 00p

         This should create an executable ./perl.exe with all the
         statically loaded extensions built in.  Compare the

perl v5.12.5         Last change: 2012-11-03                   21

Perl Programmers Reference Guide                       PERLOS2(1)

         generated perlmain.c files to make sure that during the
         iterations the number of loaded extensions only
         increases.  Rename ./perl.exe to perl_5.8.2.exe on

         When it converges, you got a functional variant of
         perl_5.8.2.exe; copy it to "perl_.exe".  You are done
         with generation of the local Perl installation.

     8.  Make sure that the installed modules are actually
         installed in the location of the new Perl, and are not
         inherited from entries of @INC given for inheritance
         from the older versions of Perl: set
         "PERLLIB_582_PREFIX" to redirect the new version of Perl
         to a new location, and copy the installed files to this
         new location.  Redo the tests to make sure that the
         versions of modules inherited from older versions of
         Perl are not needed.

         Actually, the log output of pod2ipf during the step 6
         gives a very detailed info about which modules are
         loaded from which place; so you may use it as an
         additional verification tool.

         Check that some temporary files did not make into the
         perl install tree.  Run something like this

           pfind . -f "!(/\.(pm|pl|ix|al|h|a|lib|txt|pod|imp|bs|dll|ld|bs|inc|xbm|yml|cgi|uu|e2x|skip|packlist|eg|cfg|html|pub|enc|all|ini|po|pot)$/i or /^\w+$/") | less

         in the install tree (both top one and sitelib one).

         Compress all the DLLs with lxlite.  The tiny .exe can be
         compressed with "/c:max" (the bug only appears when
         there is a fixup in the last 6 bytes of a page (?);
         since the tiny executables are much smaller than a page,
         the bug will not hit).  Do not compress "perl_.exe" - it
         would not work under DOS.

     9.  Now you can generate the binary distribution.  This is
         done by running the test of the CPAN distribution
         "OS2::SoftInstaller".  Tune up the file to suit
         the layout of current version of Perl first.  Do not
         forget to pack the necessary external DLLs accordingly.
         Include the description of the bugs and test suite
         failures you could not fix.  Include the small-stack
         versions of Perl executables from Perl build directory.

         Include perl5.def so that people can relink the perl DLL
         preserving the binary compatibility, or can create
         compatibility DLLs.  Include the diff files ("diff -pu
         old new") of fixes you did so that people can rebuild
         your version.  Include so that one can use

perl v5.12.5         Last change: 2012-11-03                   22

Perl Programmers Reference Guide                       PERLOS2(1)

         remote debugging.

     10. Share what you did with the other people.  Relax.  Enjoy
         fruits of your work.

     11. Brace yourself for thanks, bug reports, hate mail and
         spam coming as result of the previous step.  No good
         deed should remain unpunished!

Building custom .EXE files
     The Perl executables can be easily rebuilt at any moment.
     Moreover, one can use the embedding interface (see
     perlembed) to make very customized executables.

  Making executables with a custom collection of statically
     loaded extensions
     It is a little bit easier to do so while decreasing the list
     of statically loaded extensions.  We discuss this case only

     1.  Change to an empty directory, and create a placeholder

           use ExtUtils::MakeMaker;
           WriteMakefile NAME => 'dummy';

     2.  Run it with the flavor of Perl (perl.exe or perl_.exe)
         you want to rebuild.

           perl_ Makefile.PL

     3.  Ask it to create new Perl executable:

           make perl

         (you may need to manually add "PERLTYPE=-DPERL_CORE" to
         this commandline on some versions of Perl; the symptom
         is that the command-line globbing does not work from
         OS/2 shells with the newly-compiled executable; check

           .\perl.exe -wle "print for @ARGV" *


     4.  The previous step created perlmain.c which contains a
         list of newXS() calls near the end.  Removing
         unnecessary calls, and rerunning

           make perl

         will produce a customized executable.

perl v5.12.5         Last change: 2012-11-03                   23

Perl Programmers Reference Guide                       PERLOS2(1)

  Making executables with a custom search-paths
     The default perl executable is flexible enough to support
     most usages.  However, one may want something yet more
     flexible; for example, one may want to find Perl DLL
     relatively to the location of the EXE file; or one may want
     to ignore the environment when setting the Perl-library
     search patch, etc.

     If you fill comfortable with embedding interface (see
     perlembed), such things are easy to do repeating the steps
     outlined in "Making executables with a custom collection of
     statically loaded extensions", and doing more comprehensive
     edits to main() of perlmain.c.  The people with little
     desire to understand Perl can just rename main(), and do
     necessary modification in a custom main() which calls the
     renamed function in appropriate time.

     However, there is a third way: perl DLL exports the main()
     function and several callbacks to customize the search path.
     Below is a complete example of a "Perl loader" which

     1.  Looks for Perl DLL in the directory "$exedir/../dll";

     2.  Prepends the above directory to "BEGINLIBPATH";

     3.  Fails if the Perl DLL found via "BEGINLIBPATH" is
         different from what was loaded on step 1; e.g., another
         process could have loaded it from "LIBPATH" or from a
         different value of "BEGINLIBPATH".  In these cases one
         needs to modify the setting of the system so that this
         other process either does not run, or loads the DLL from
         "BEGINLIBPATH" with "LIBPATHSTRICT=T" (available with
         kernels after September 2000).

     4.  Loads Perl library from "$exedir/../dll/lib/".

     5.  Uses Bourne shell from "$exedir/../dll/sh/ksh.exe".

     For best results compile the C file below with the same
     options as the Perl DLL.  However, a lot of functionality
     will work even if the executable is not an EMX applications,
     e.g., if compiled with

       gcc -Wall -DDOSISH -DOS2=1 -O2 -s -Zomf -Zsys perl-starter.c -DPERL_DLL_BASENAME=\"perl312F\" -Zstack 8192 -Zlinker /PM:VIO

     Here is the sample C file:

       #define INCL_DOS
       #define INCL_NOPM
       /* These are needed for compile if os2.h includes os2tk.h, not os2emx.h */
       #define INCL_DOSPROCESS
       #include <os2.h>

perl v5.12.5         Last change: 2012-11-03                   24

Perl Programmers Reference Guide                       PERLOS2(1)

       #include "EXTERN.h"
       #include "perl.h"

       static char *me;
       HMODULE handle;

       static void
       die_with(char *msg1, char *msg2, char *msg3, char *msg4)
          ULONG c;
          char *s = " error: ";

          DosWrite(2, me, strlen(me), &c);
          DosWrite(2, s, strlen(s), &c);
          DosWrite(2, msg1, strlen(msg1), &c);
          DosWrite(2, msg2, strlen(msg2), &c);
          DosWrite(2, msg3, strlen(msg3), &c);
          DosWrite(2, msg4, strlen(msg4), &c);
          DosWrite(2, "\r\n", 2, &c);

       typedef ULONG (*fill_extLibpath_t)(int type, char *pre, char *post, int replace, char *msg);
       typedef int (*main_t)(int type, char *argv[], char *env[]);
       typedef int (*handler_t)(void* data, int which);

       #ifndef PERL_DLL_BASENAME
       #  define PERL_DLL_BASENAME "perl"

       static HMODULE
       load_perl_dll(char *basename)
           char buf[300], fail[260];
           STRLEN l, dirl;
           fill_extLibpath_t f;
           ULONG rc_fullname;
           HMODULE handle, handle1;

           if (_execname(buf, sizeof(buf) - 13) != 0)
               die_with("Can't find full path: ", strerror(errno), "", "");
           /* XXXX Fill `me' with new value */
           l = strlen(buf);
           while (l && buf[l-1] != '/' && buf[l-1] != '\\')
           dirl = l - 1;
           strcpy(buf + l, basename);
           l += strlen(basename);
           strcpy(buf + l, ".dll");
           if ( (rc_fullname = DosLoadModule(fail, sizeof fail, buf, &handle)) != 0

perl v5.12.5         Last change: 2012-11-03                   25

Perl Programmers Reference Guide                       PERLOS2(1)

                && DosLoadModule(fail, sizeof fail, basename, &handle) != 0 )
               die_with("Can't load DLL ", buf, "", "");
           if (rc_fullname)
               return handle;                /* was loaded with short name; all is fine */
           if (DosQueryProcAddr(handle, 0, "fill_extLibpath", (PFN*)&f))
               die_with(buf, ": DLL exports no symbol ", "fill_extLibpath", "");
           buf[dirl] = 0;
           if (f(0 /*BEGINLIBPATH*/, buf /* prepend */, NULL /* append */,
                 0 /* keep old value */, me))
               die_with(me, ": prepending BEGINLIBPATH", "", "");
           if (DosLoadModule(fail, sizeof fail, basename, &handle1) != 0)
               die_with(me, ": finding perl DLL again via BEGINLIBPATH", "", "");
           buf[dirl] = '\\';
           if (handle1 != handle) {
               if (DosQueryModuleName(handle1, sizeof(fail), fail))
                   strcpy(fail, "???");
               die_with(buf, ":\n\tperl DLL via BEGINLIBPATH is different: \n\t",
                        "\n\tYou may need to manipulate global BEGINLIBPATH and LIBPATHSTRICT"
                        "\n\tso that the other copy is loaded via BEGINLIBPATH.");
           return handle;

       main(int argc, char **argv, char **env)
           main_t f;
           handler_t h;

           me = argv[0];
           handle = load_perl_dll(PERL_DLL_BASENAME);

           if (DosQueryProcAddr(handle, 0, "Perl_OS2_handler_install", (PFN*)&h))
               die_with(PERL_DLL_BASENAME, ": DLL exports no symbol ", "Perl_OS2_handler_install", "");
           if ( !h((void *)"~installprefix", Perlos2_handler_perllib_from)
                || !h((void *)"~dll", Perlos2_handler_perllib_to)
                || !h((void *)"~dll/sh/ksh.exe", Perlos2_handler_perl_sh) )
               die_with(PERL_DLL_BASENAME, ": Can't install @INC manglers", "", "");

           if (DosQueryProcAddr(handle, 0, "dll_perlmain", (PFN*)&f))
               die_with(PERL_DLL_BASENAME, ": DLL exports no symbol ", "dll_perlmain", "");
           return f(argc, argv, env);

Build FAQ
  Some "/" became "\" in pdksh.
     You have a very old pdksh. See Prerequisites.

  'errno' - unresolved external
     You do not have MT-safe db.lib. See Prerequisites.

perl v5.12.5         Last change: 2012-11-03                   26

Perl Programmers Reference Guide                       PERLOS2(1)

  Problems with tr or sed
     reported with very old version of tr and sed.

  Some problem (forget which ;-)
     You have an older version of perl.dll on your LIBPATH, which
     broke the build of extensions.

  Library ... not found
     You did not run "omflibs". See Prerequisites.

  Segfault in make
     You use an old version of GNU make. See Prerequisites.

  op/sprintf test failure
     This can result from a bug in emx sprintf which was fixed in
     0.9d fix 03.

Specific (mis)features of OS/2 port
  "setpriority", "getpriority"
     Note that these functions are compatible with *nix, not with
     the older ports of '94 - 95. The priorities are absolute, go
     from 32 to -95, lower is quicker. 0 is the default priority.

     WARNING.  Calling "getpriority" on a non-existing process
     could lock the system before Warp3 fixpak22.  Starting with
     Warp3, Perl will use a workaround: it aborts getpriority()
     if the process is not present.  This is not possible on
     older versions "2.*", and has a race condition anyway.

     Multi-argument form of "system()" allows an additional
     numeric argument. The meaning of this argument is described
     in OS2::Process.

     When finding a program to run, Perl first asks the OS to
     look for executables on "PATH" (OS/2 adds extension .exe if
     no extension is present).  If not found, it looks for a
     script with possible extensions added in this order: no
     extension, .cmd, .btm, .bat, .pl.  If found, Perl checks the
     start of the file for magic strings "#!" and "extproc ".  If
     found, Perl uses the rest of the first line as the beginning
     of the command line to run this script.  The only mangling
     done to the first line is extraction of arguments (currently
     up to 3), and ignoring of the path-part of the "interpreter"
     name if it can't be found using the full path.

     E.g., "system 'foo', 'bar', 'baz'" may lead Perl to finding
     C:/emx/bin/foo.cmd with the first line being

      extproc /bin/bash    -x   -c

perl v5.12.5         Last change: 2012-11-03                   27

Perl Programmers Reference Guide                       PERLOS2(1)

     If /bin/bash.exe is not found, then Perl looks for an
     executable bash.exe on "PATH".  If found in
     C:/emx.add/bin/bash.exe, then the above system() is
     translated to

       system qw(C:/emx.add/bin/bash.exe -x -c C:/emx/bin/foo.cmd bar baz)

     One additional translation is performed: instead of /bin/sh
     Perl uses the hardwired-or-customized shell (see

     The above search for "interpreter" is recursive: if bash
     executable is not found, but bash.btm is found, Perl will
     investigate its first line etc.  The only hardwired limit on
     the recursion depth is implicit: there is a limit 4 on the
     number of additional arguments inserted before the actual
     arguments given to system().  In particular, if no
     additional arguments are specified on the "magic" first
     lines, then the limit on the depth is 4.

     If Perl finds that the found executable is of PM type when
     the current session is not, it will start the new process in
     a separate session of necessary type.  Call via
     "OS2::Process" to disable this magic.

     WARNING.  Due to the described logic, you need to explicitly
     specify .com extension if needed.  Moreover, if the
     executable perl5.6.1 is requested, Perl will not look for
     perl5.6.1.exe.  [This may change in the future.]

  "extproc" on the first line
     If the first chars of a Perl script are "extproc ", this
     line is treated as "#!"-line, thus all the switches on this
     line are processed (twice if script was started via
     cmd.exe).  See "DESCRIPTION" in perlrun.

  Additional modules:
     OS2::Process, OS2::DLL, OS2::REXX, OS2::PrfDB, OS2::ExtAttr.
     These modules provide access to additional numeric argument
     for "system" and to the information about the running
     process, to DLLs having functions with REXX signature and to
     the REXX runtime, to OS/2 databases in the .INI format, and
     to Extended Attributes.

     Two additional extensions by Andreas Kaiser, "OS2::UPM", and
     "OS2::FTP", are included into "ILYAZ" directory, mirrored on
     CPAN.  Other OS/2-related extensions are available too.

  Prebuilt methods:
         used by "File::Copy::copy", see File::Copy.

perl v5.12.5         Last change: 2012-11-03                   28

Perl Programmers Reference Guide                       PERLOS2(1)

         used by "DynaLoader" for DLL name mangling.

         Self explanatory.

         leaves drive as it is.

         chanes the "current" drive.

         means has drive letter and is_rooted.

         means has leading "[/\\]" (maybe after a drive-letter:).

         means changes with current dir.

         Interface to cwd from EMX. Used by "Cwd::cwd".

     "Cwd::sys_abspath(name, dir)"
         Really really odious function to implement. Returns
         absolute name of file which would have "name" if CWD
         were "dir".  "Dir" defaults to the current dir.

         Get current value of extended library search path. If
         "type" is present and positive, works with
         "END_LIBPATH", if negative, works with "LIBPATHSTRICT",
         otherwise with "BEGIN_LIBPATH".

     "Cwd::extLibpath_set( path [, type ] )"
         Set current value of extended library search path. If
         "type" is present and positive, works with
         <END_LIBPATH>, if negative, works with "LIBPATHSTRICT",
         otherwise with "BEGIN_LIBPATH".

         Returns   "undef" if it was not called yet, otherwise
         bit 1 is set if on the previous call do_harderror was
         enabled, bit 2 is set if on previous call do_exception
         was enabled.

         This function enables/disables error popups associated
         with hardware errors (Disk not ready etc.) and software

         I know of no way to find out the state of popups before

perl v5.12.5         Last change: 2012-11-03                   29

Perl Programmers Reference Guide                       PERLOS2(1)

         the first call to this function.

         Returns "undef" if it was not called yet, otherwise
         return false if errors were not requested to be written
         to a hard drive, or the drive letter if this was

         This function may redirect error popups associated with
         hardware errors (Disk not ready etc.) and software
         exceptions to the file POPUPLOG.OS2 at the root
         directory of the specified drive.  Overrides
         OS2::Error() specified by individual programs.  Given
         argument undef will disable redirection.

         Has global effect, persists after the application exits.

         I know of no way to find out the state of redirection of
         popups to the disk before the first call to this

         Returns a hash with system information. The keys of the
         hash are


         Returns a letter without colon.

     "OS2::MorphPM(serve)", "OS2::UnMorphPM(serve)"
         Transforms the current application into a PM application
         and back.  The argument true means that a real message
         loop is going to be served.  OS2::MorphPM() returns the
         PM message queue handle as an integer.

         See "Centralized management of resources" for additional

         Fake on-demand retrieval of outstanding PM messages.  If
         "force" is false, will not dispatch messages if a real
         message loop is known to be present.  Returns number of
         messages retrieved.

perl v5.12.5         Last change: 2012-11-03                   30

Perl Programmers Reference Guide                       PERLOS2(1)

         Dies with "QUITing..." if WM_QUIT message is obtained.

     "OS2::Process_Messages(force [, cnt])"
         Retrieval of PM messages until window
         creation/destruction.  If "force" is false, will not
         dispatch messages if a real message loop is known to be

         Returns change in number of windows.  If "cnt" is given,
         it is incremented by the number of messages retrieved.

         Dies with "QUITing..." if WM_QUIT message is obtained.

         the same as _control87(3) of EMX.  Takes integers as
         arguments, returns the previous coprocessor control word
         as an integer.  Only bits in "new" which are present in
         "mask" are changed in the control word.

         gets the coprocessor control word as an integer.

         The variant of OS2::_control87() with default values
         good for handling exception mask: if no "mask", uses
         exception mask part of "new" only.  If no "new",
         disables all the floating point exceptions.

         See "Misfeatures" for details.

     "OS2::DLLname([how [, \&xsub]])"
         Gives the information about the Perl DLL or the DLL
         containing the C function bound to by &xsub.  The
         meaning of "how" is: default (2): full name; 0: handle;
         1: module name.

     (Note that some of these may be moved to different libraries
     - eventually).

  Prebuilt variables:
         numeric value is the same as _emx_rev of EMX, a string
         value the same as _emx_vprt (similar to "0.9c").

         same as _emx_env of EMX, a number similar to 0x8001.

         a number "OS_MAJOR + 0.001 * OS_MINOR".

         true if the Perl library was compiled in AOUT format.

perl v5.12.5         Last change: 2012-11-03                   31

Perl Programmers Reference Guide                       PERLOS2(1)

         true if the current executable is an AOUT EMX
         executable, so Perl can fork.  Do not use this, use the
         portable check for $Config::Config{dfork}.

         This variable (default is 1) controls whether to enforce
         the contents of $^E to start with "SYS0003"-like id.  If
         set to 0, then the string value of $^E is what is
         available from the OS/2 message file.  (Some messages in
         this file have an "SYS0003"-like id prepended, some

     o   Since flock(3) is present in EMX, but is not functional,
         it is emulated by perl.  To disable the emulations, set
         environment variable "USE_PERL_FLOCK=0".

     o   Here is the list of things which may be "broken" on EMX
         (from EMX docs):

         o   The functions recvmsg(3), sendmsg(3), and
             socketpair(3) are not implemented.

         o   sock_init(3) is not required and not implemented.

         o   flock(3) is not yet implemented (dummy function).
             (Perl has a workaround.)

         o   kill(3):  Special treatment of PID=0, PID=1 and
             PID=-1 is not implemented.

         o   waitpid(3):

                           Not implemented.
                   waitpid() is not implemented for negative values of PID.

         Note that "kill -9" does not work with the current
         version of EMX.

     o   See "Text-mode filehandles".

     o   Unix-domain sockets on OS/2 live in a pseudo-file-system
         "/sockets/...".  To avoid a failure to create a socket
         with a name of a different form, "/socket/" is prepended
         to the socket name (unless it starts with this already).

         This may lead to problems later in case the socket is
         accessed via the "usual" file-system calls using the
         "initial" name.

perl v5.12.5         Last change: 2012-11-03                   32

Perl Programmers Reference Guide                       PERLOS2(1)

     o   Apparently, IBM used a compiler (for some period of time
         around '95?) which changes FP mask right and left.  This
         is not that bad for IBM's programs, but the same
         compiler was used for DLLs which are used with general-
         purpose applications.  When these DLLs are used, the
         state of floating-point flags in the application is not

         What is much worse, some DLLs change the floating point
         flags when in _DLLInitTerm() (e.g., TCP32IP).  This
         means that even if you do not call any function in the
         DLL, just the act of loading this DLL will reset your
         flags.  What is worse, the same compiler was used to
         compile some HOOK DLLs.  Given that HOOK dlls are
         executed in the context of all the applications in the
         system, this means a complete unpredictablity of
         floating point flags on systems using such HOOK DLLs.
         E.g., GAMESRVR.DLL of DIVE origin changes the floating
         point flags on each write to the TTY of a VIO (windowed
         text-mode) applications.

         Some other (not completely debugged) situations when FP
         flags change include some video drivers (?), and some
         operations related to creation of the windows.  People
         who code OpenGL may have more experience on this.

         Perl is generally used in the situation when all the
         floating-point exceptions are ignored, as is the default
         under EMX.  If they are not ignored, some benign Perl
         programs would get a "SIGFPE" and would die a horrible

         To circumvent this, Perl uses two hacks.  They help
         against one type of damage only: FP flags changed when
         loading a DLL.

         One of the hacks is to disable floating point exceptions
         on Perl startup (as is the default with EMX).  This
         helps only with compile-time-linked DLLs changing the
         flags before main() had a chance to be called.

         The other hack is to restore FP flags after a call to
         dlopen().  This helps against similar damage done by
         DLLs _DLLInitTerm() at runtime.  Currently no way to
         switch these hacks off is provided.

     Perl modifies some standard C library calls in the following

     "popen"  "my_popen" uses sh.exe if shell is required, cf.

perl v5.12.5         Last change: 2012-11-03                   33

Perl Programmers Reference Guide                       PERLOS2(1)

     "tmpnam" is created using "TMP" or "TEMP" environment
              variable, via "tempnam".

              If the current directory is not writable, file is
              created using modified "tmpnam", so there may be a
              race condition.

              a dummy implementation.

     "stat"   "os2_stat" special-cases /dev/tty and /dev/con.

     "mkdir", "rmdir"
              these EMX functions do not work if the path
              contains a trailing "/".  Perl contains a
              workaround for this.

     "flock"  Since flock(3) is present in EMX, but is not
              functional, it is emulated by perl.  To disable the
              emulations, set environment variable

  Identifying DLLs
     All the DLLs built with the current versions of Perl have ID
     strings identifying the name of the extension, its version,
     and the version of Perl required for this DLL.  Run
     "bldlevel DLL-name" to find this info.

  Centralized management of resources
     Since to call certain OS/2 API one needs to have a correctly
     initialized "Win" subsystem, OS/2-specific extensions may
     require getting "HAB"s and "HMQ"s.  If an extension would do
     it on its own, another extension could fail to initialize.

     Perl provides a centralized management of these resources:

         To get the HAB, the extension should call "hab =
         perl_hab_GET()" in C.  After this call is performed,
         "hab" may be accessed as "Perl_hab".  There is no need
         to release the HAB after it is used.

         If by some reasons perl.h cannot be included, use

           extern int Perl_hab_GET(void);


         There are two cases:

perl v5.12.5         Last change: 2012-11-03                   34

Perl Programmers Reference Guide                       PERLOS2(1)

         o   the extension needs an "HMQ" only because some API
             will not work otherwise.  Use "serve = 0" below.

         o   the extension needs an "HMQ" since it wants to
             engage in a PM event loop.  Use "serve = 1" below.

         To get an "HMQ", the extension should call "hmq =
         perl_hmq_GET(serve)" in C.  After this call is
         performed, "hmq" may be accessed as "Perl_hmq".

         To signal to Perl that HMQ is not needed any more, call
         "perl_hmq_UNSET(serve)".  Perl process will
         automatically morph/unmorph itself into/from a PM
         process if HMQ is needed/not-needed.  Perl will
         automatically enable/disable "WM_QUIT" message during
         shutdown if the message queue is served/not-served.

         NOTE.  If during a shutdown there is a message queue
         which did not disable WM_QUIT, and which did not process
         the received WM_QUIT message, the shutdown will be
         automatically cancelled.  Do not call perl_hmq_GET(1)
         unless you are going to process messages on an orderly

     * Treating errors reported by OS/2 API
         There are two principal conventions (it is useful to
         call them "Dos*" and "Win*" - though this part of the
         function signature is not always determined by the name
         of the API) of reporting the error conditions of OS/2
         API.  Most of "Dos*" APIs report the error code as the
         result of the call (so 0 means success, and there are
         many types of errors).  Most of "Win*" API report
         success/fail via the result being "TRUE"/"FALSE"; to
         find the reason for the failure one should call
         WinGetLastError() API.

         Some "Win*" entry points also overload a "meaningful"
         return value with the error indicator; having a 0 return
         value indicates an error.  Yet some other "Win*" entry
         points overload things even more, and 0 return value may
         mean a successful call returning a valid value 0, as
         well as an error condition; in the case of a 0 return
         value one should call WinGetLastError() API to
         distinguish a successful call from a failing one.

         By convention, all the calls to OS/2 API should indicate
         their failures by resetting $^E.  All the Perl-
         accessible functions which call OS/2 API may be broken
         into two classes: some die()s when an API error is
         encountered, the other report the error via a false
         return value (of course, this does not concern Perl-
         accessible functions which expect a failure of the OS/2

perl v5.12.5         Last change: 2012-11-03                   35

Perl Programmers Reference Guide                       PERLOS2(1)

         API call, having some workarounds coded).

         Obviously, in the situation of the last type of the
         signature of an OS/2 API, it is must more convenient for
         the users if the failure is indicated by die()ing: one
         does not need to check $^E to know that something went
         wrong.  If, however, this solution is not desirable by
         some reason, the code in question should reset $^E to 0
         before making this OS/2 API call, so that the caller of
         this Perl-accessible function has a chance to
         distinguish a success-but-0-return value from a failure.
         (One may return undef as an alternative way of reporting
         an error.)

         The macros to simplify this type of error propagation

             Returns true on error, sets $^E.  Expects expr() be
             a call of "Dos*"-style API.

             Returns true on error, sets $^E.  Expects expr() be
             a call of "Win*"-style API.

             Returns "expr", sets $^E from WinGetLastError() if
             "expr" is false.

             Returns "expr", sets $^E from WinGetLastError() if
             "expr" is false, and die()s if "die" and $^E are
             true.  The message to die is the concatenated
             strings "name1" and "name2", separated by ": " from
             the contents of $^E.

             Sets "Perl_rc" to the return value of

             Sets "Perl_rc" to the return value of
             WinGetLastError(), and sets $^E to the corresponding

             Sets "Perl_rc" to "rc", and sets $^E to the
             corresponding value.

     * Loading DLLs and ordinals in DLLs
         Some DLLs are only present in some versions of OS/2, or
         in some configurations of OS/2.  Some exported entry

perl v5.12.5         Last change: 2012-11-03                   36

Perl Programmers Reference Guide                       PERLOS2(1)

         points are present only in DLLs shipped with some
         versions of OS/2.  If these DLLs and entry points were
         linked directly for a Perl executable/DLL or from a Perl
         extensions, this binary would work only with the
         specified versions/setups.  Even if these entry points
         were not needed, the load of the executable (or DLL)
         would fail.

         For example, many newer useful APIs are not present in
         OS/2 v2; many PM-related APIs require DLLs not available
         on floppy-boot setup.

         To make these calls fail only when the calls are
         executed, one should call these API via a dynamic
         linking API.  There is a subsystem in Perl to simplify
         such type of calls.  A large number of entry points
         available for such linking is provided (see
         "entries_ordinals" - and also "PMWIN_entries" - in
         os2ish.h).  These ordinals can be accessed via the APIs:

           CallORD(), DeclFuncByORD(), DeclVoidFuncByORD(),
           DeclOSFuncByORD(), DeclWinFuncByORD(), AssignFuncPByORD(),
           DeclWinFuncByORD_CACHE(), DeclWinFuncByORD_CACHE_survive(),
           DeclWinFunc_CACHE(), DeclWinFunc_CACHE_resetError(),
           DeclWinFunc_CACHE_survive(), DeclWinFunc_CACHE_resetError_survive()

         See the header files and the C code in the supplied
         OS/2-related modules for the details on usage of these

         Some of these functions also combine dynaloading
         semantic with the error-propagation semantic discussed

Perl flavors
     Because of idiosyncrasies of OS/2 one cannot have all the
     eggs in the same basket (though EMX environment tries hard
     to overcome this limitations, so the situation may somehow
     improve). There are 4 executables for Perl provided by the

     The main workhorse. This is a chimera executable: it is
     compiled as an "a.out"-style executable, but is linked with
     "omf"-style dynamic library perl.dll, and with dynamic CRT
     DLL. This executable is a VIO application.

     It can load perl dynamic extensions, and it can fork().

     Note. Keep in mind that fork() is needed to open a pipe to

perl v5.12.5         Last change: 2012-11-03                   37

Perl Programmers Reference Guide                       PERLOS2(1)

     This is a statically linked "a.out"-style executable. It
     cannot load dynamic Perl extensions. The executable supplied
     in binary distributions has a lot of extensions prebuilt,
     thus the above restriction is important only if you use
     custom-built extensions. This executable is a VIO

     This is the only executable with does not require OS/2. The
     friends locked into "M$" world would appreciate the fact
     that this executable runs under DOS, Win0.3*, Win0.95 and
     WinNT with an appropriate extender. See "Other OSes".

     This is the same executable as perl___.exe, but it is a PM

     Note. Usually (unless explicitly redirected during the
     startup) STDIN, STDERR, and STDOUT of a PM application are
     redirected to nul. However, it is possible to see them if
     you start "perl__.exe" from a PM program which emulates a
     console window, like Shell mode of Emacs or EPM. Thus it is
     possible to use Perl debugger (see perldebug) to debug your
     PM application (but beware of the message loop lockups -
     this will not work if you have a message queue to serve,
     unless you hook the serving into the getc() function of the

     Another way to see the output of a PM program is to run it

       pm_prog args 2>&1 | cat -

     with a shell different from cmd.exe, so that it does not
     create a link between a VIO session and the session of
     "pm_porg".  (Such a link closes the VIO window.)  E.g., this
     works with sh.exe - or with Perl!

       open P, 'pm_prog args 2>&1 |' or die;
       print while <P>;

     The flavor perl__.exe is required if you want to start your
     program without a VIO window present, but not "detach"ed
     (run "help detach" for more info).  Very useful for
     extensions which use PM, like "Perl/Tk" or "OpenGL".

     Note also that the differences between PM and VIO
     executables are only in the default behaviour.  One can
     start any executable in any kind of session by using the
     arguments "/fs", "/pm" or "/win" switches of the command
     "start" (of CMD.EXE or a similar shell).  Alternatively, one
     can use the numeric first argument of the "system" Perl

perl v5.12.5         Last change: 2012-11-03                   38

Perl Programmers Reference Guide                       PERLOS2(1)

     function (see OS2::Process).

     This is an "omf"-style executable which is dynamically
     linked to perl.dll and CRT DLL. I know no advantages of this
     executable over "perl.exe", but it cannot fork() at all.
     Well, one advantage is that the build process is not so
     convoluted as with "perl.exe".

     It is a VIO application.

  Why strange names?
     Since Perl processes the "#!"-line (cf.  "DESCRIPTION" in
     perlrun, "Switches" in perlrun, "Not a perl script" in
     perldiag, "No Perl script found in input" in perldiag), it
     should know when a program is a Perl. There is some naming
     convention which allows Perl to distinguish correct lines
     from wrong ones. The above names are almost the only names
     allowed by this convention which do not contain digits
     (which have absolutely different semantics).

  Why dynamic linking?
     Well, having several executables dynamically linked to the
     same huge library has its advantages, but this would not
     substantiate the additional work to make it compile. The
     reason is the complicated-to-developers but very quick and
     convenient-to-users "hard" dynamic linking used by OS/2.

     There are two distinctive features of the dyna-linking model
     of OS/2: first, all the references to external functions are
     resolved at the compile time; second, there is no runtime
     fixup of the DLLs after they are loaded into memory.  The
     first feature is an enormous advantage over other models: it
     avoids conflicts when several DLLs used by an application
     export entries with the same name.  In such cases "other"
     models of dyna-linking just choose between these two entry
     points using some random criterion - with predictable
     disasters as results.  But it is the second feature which
     requires the build of perl.dll.

     The address tables of DLLs are patched only once, when they
     are loaded. The addresses of the entry points into DLLs are
     guaranteed to be the same for all the programs which use the
     same DLL.  This removes the runtime fixup - once DLL is
     loaded, its code is read-only.

     While this allows some (significant?) performance
     advantages, this makes life much harder for developers,
     since the above scheme makes it impossible for a DLL to be
     "linked" to a symbol in the .EXE file.  Indeed, this would
     need a DLL to have different relocations tables for the
     (different) executables which use this DLL.

perl v5.12.5         Last change: 2012-11-03                   39

Perl Programmers Reference Guide                       PERLOS2(1)

     However, a dynamically loaded Perl extension is forced to
     use some symbols from the perl executable, e.g., to know how
     to find the arguments to the functions: the arguments live
     on the perl internal evaluation stack. The solution is to
     put the main code of the interpreter into a DLL, and make
     the .EXE file which just loads this DLL into memory and
     supplies command-arguments.  The extension DLL cannot link
     to symbols in .EXE, but it has no problem linking to symbols
     in the .DLL.

     This greatly increases the load time for the application (as
     well as complexity of the compilation). Since interpreter is
     in a DLL, the C RTL is basically forced to reside in a DLL
     as well (otherwise extensions would not be able to use CRT).
     There are some advantages if you use different flavors of
     perl, such as running perl.exe and perl__.exe
     simultaneously: they share the memory of perl.dll.

     NOTE.  There is one additional effect which makes DLLs more
     wasteful: DLLs are loaded in the shared memory region, which
     is a scarse resource given the 512M barrier of the
     "standard" OS/2 virtual memory.  The code of .EXE files is
     also shared by all the processes which use the particular
     .EXE, but they are "shared in the private address space of
     the process"; this is possible because the address at which
     different sections of the .EXE file are loaded is decided at
     compile-time, thus all the processes have these sections
     loaded at same addresses, and no fixup of internal links
     inside the .EXE is needed.

     Since DLLs may be loaded at run time, to have the same
     mechanism for DLLs one needs to have the address range of
     any of the loaded DLLs in the system to be available in all
     the processes which did not load a particular DLL yet.  This
     is why the DLLs are mapped to the shared memory region.

  Why chimera build?
     Current EMX environment does not allow DLLs compiled using
     Unixish "a.out" format to export symbols for data (or at
     least some types of data). This forces "omf"-style compile
     of perl.dll.

     Current EMX environment does not allow .EXE files compiled
     in "omf" format to fork(). fork() is needed for exactly
     three Perl operations:

     o   explicit fork() in the script,

     o   "open FH, "|-""

     o   "open FH, "-|"", in other words, opening pipes to

perl v5.12.5         Last change: 2012-11-03                   40

Perl Programmers Reference Guide                       PERLOS2(1)

     While these operations are not questions of life and death,
     they are needed for a lot of useful scripts. This forces
     "a.out"-style compile of perl.exe.

     Here we list environment variables with are either OS/2- and
     DOS- and Win*-specific, or are more important under OS/2
     than under other OSes.

     Specific for EMX port. Should have the form



       path1 path2

     If the beginning of some prebuilt path matches path1, it is
     substituted with path2.

     Should be used if the perl library is moved from the default
     location in preference to "PERL(5)LIB", since this would not
     leave wrong entries in @INC.  For example, if the compiled
     version of perl looks for @INC in f:/perllib/lib, and you
     want to install the library in h:/opt/gnu, do

       set PERLLIB_PREFIX=f:/perllib/lib;h:/opt/gnu

     This will cause Perl with the prebuilt @INC of


     to use the following @INC:


     If 0, perl ignores setlocale() failing. May be useful with
     some strange locales.

     If 0, perl would not warn of in case of unwarranted free().
     With older perls this might be useful in conjunction with

perl v5.12.5         Last change: 2012-11-03                   41

Perl Programmers Reference Guide                       PERLOS2(1)

     the module DB_File, which was buggy when dynamically linked
     and OMF-built.

     Should not be set with newer Perls, since this may hide some
     real problems.

     Specific for EMX port. Gives the directory part of the
     location for sh.exe.

     Specific for EMX port. Since flock(3) is present in EMX, but
     is not functional, it is emulated by perl.  To disable the
     emulations, set environment variable "USE_PERL_FLOCK=0".

  "TMP" or "TEMP"
     Specific for EMX port. Used as storage place for temporary

     Here we list major changes which could make you by surprise.

  Text-mode filehandles
     Starting from version 5.8, Perl uses a builtin translation
     layer for text-mode files.  This replaces the efficient
     well-tested EMX layer by some code which should be best
     characterized as a "quick hack".

     In addition to possible bugs and an inability to follow
     changes to the translation policy with off/on switches of
     TERMIO translation, this introduces a serious incompatible
     change: before sysread() on text-mode filehandles would go
     through the translation layer, now it would not.

     "setpriority" and "getpriority" are not compatible with
     earlier ports by Andreas Kaiser. See "setpriority,

  DLL name mangling: pre 5.6.2
     With the release 5.003_01 the dynamically loadable libraries
     should be rebuilt when a different version of Perl is
     compiled. In particular, DLLs (including perl.dll) are now
     created with the names which contain a checksum, thus
     allowing workaround for OS/2 scheme of caching DLLs.

     It may be possible to code a simple workaround which would

     o   find the old DLLs looking through the old @INC;

     o   mangle the names according to the scheme of new perl and
         copy the DLLs to these names;

perl v5.12.5         Last change: 2012-11-03                   42

Perl Programmers Reference Guide                       PERLOS2(1)

     o   edit the internal "LX" tables of DLL to reflect the
         change of the name (probably not needed for Perl
         extension DLLs, since the internally coded names are not
         used for "specific" DLLs, they used only for "global"

     o   edit the internal "IMPORT" tables and change the name of
         the "old" perl????.dll to the "new" perl????.dll.

  DLL name mangling: 5.6.2 and beyond
     In fact mangling of extension DLLs was done due to
     misunderstanding of the OS/2 dynaloading model.  OS/2
     (effectively) maintains two different tables of loaded DLL:

     Global DLLs
         those loaded by the base name from "LIBPATH"; including
         those associated at link time;

     specific DLLs
         loaded by the full name.

     When resolving a request for a global DLL, the table of
     already-loaded specific DLLs is (effectively) ignored;
     moreover, specific DLLs are always loaded from the
     prescribed path.

     There is/was a minor twist which makes this scheme fragile:
     what to do with DLLs loaded from

         (which depend on the process)

     . from "LIBPATH"
         which effectively depends on the process (although
         "LIBPATH" is the same for all the processes).

     Unless "LIBPATHSTRICT" is set to "T" (and the kernel is
     after 2000/09/01), such DLLs are considered to be global.
     When loading a global DLL it is first looked in the table of
     already-loaded global DLLs.  Because of this the fact that
     one executable loaded a DLL from "BEGINLIBPATH" and
     "ENDLIBPATH", or . from "LIBPATH" may affect which DLL is
     loaded when another executable requests a DLL with the same
     name.  This is the reason for version-specific mangling of
     the DLL name for perl DLL.

     Since the Perl extension DLLs are always loaded with the
     full path, there is no need to mangle their names in a
     version-specific ways: their directory already reflects the
     corresponding version of perl, and @INC takes into account
     binary compatibility with older version.  Starting from
     5.6.2 the name mangling scheme is fixed to be the same as

perl v5.12.5         Last change: 2012-11-03                   43

Perl Programmers Reference Guide                       PERLOS2(1)

     for Perl 5.005_53 (same as in a popular binary release).
     Thus new Perls will be able to resolve the names of old
     extension DLLs if @INC allows finding their directories.

     However, this still does not guarantee that these DLL may be
     loaded.  The reason is the mangling of the name of the Perl
     DLL.  And since the extension DLLs link with the Perl DLL,
     extension DLLs for older versions would load an older Perl
     DLL, and would most probably segfault (since the data in
     this DLL is not properly initialized).

     There is a partial workaround (which can be made complete
     with newer OS/2 kernels): create a forwarder DLL with the
     same name as the DLL of the older version of Perl, which
     forwards the entry points to the newer Perl's DLL.  Make
     this DLL accessible on (say) the "BEGINLIBPATH" of the new
     Perl executable.  When the new executable accesses old
     Perl's extension DLLs, they would request the old Perl's DLL
     by name, get the forwarder instead, so effectively will link
     with the currently running (new) Perl DLL.

     This may break in two ways:

     o   Old perl executable is started when a new executable is
         running has loaded an extension compiled for the old
         executable (ouph!).  In this case the old executable
         will get a forwarder DLL instead of the old perl DLL, so
         would link with the new perl DLL.  While not directly
         fatal, it will behave the same as new executable.  This
         beats the whole purpose of explicitly starting an old

     o   A new executable loads an extension compiled for the old
         executable when an old perl executable is running.  In
         this case the extension will not pick up the forwarder -
         with fatal results.

     With support for "LIBPATHSTRICT" this may be circumvented -
     unless one of DLLs is started from . from "LIBPATH" (I do
     not know whether "LIBPATHSTRICT" affects this case).

     REMARK.  Unless newer kernels allow . in "BEGINLIBPATH"
     (older do not), this mess cannot be completely cleaned.  (It
     turns out that as of the beginning of 2002, . is not
     allowed, but .\. is - and it has the same effect.)

     are not environment variables, although cmd.exe emulates
     them on "SET ..." lines.  From Perl they may be accessed by
     Cwd::extLibpath and Cwd::extLibpath_set.

perl v5.12.5         Last change: 2012-11-03                   44

Perl Programmers Reference Guide                       PERLOS2(1)

  DLL forwarder generation
     Assume that the old DLL is named perlE0AC.dll (as is one for
     5.005_53), and the new version is 5.6.1.  Create a file
     perl5shim.def-leader with

       DESCRIPTION ' Perl module for 5.00553 -> Perl 5.6.1 forwarder'

     modifying the versions/names as needed.  Run

      perl -wnle "next if 0../EXPORTS/; print qq(  \"$1\") if /\"(\w+)\"/" perl5.def >lst

     in the Perl build directory (to make the DLL smaller replace
     perl5.def with the definition file for the older version of
     Perl if present).

      cat perl5shim.def-leader lst >perl5shim.def
      gcc -Zomf -Zdll -o perlE0AC.dll perl5shim.def -s -llibperl

     (ignore multiple "warning L4085").

     As of release 5.003_01 perl is linked to multithreaded C RTL
     DLL.  If perl itself is not compiled multithread-enabled, so
     will not be perl's malloc(). However, extensions may use
     multiple thread on their own risk.

     This was needed to compile "Perl/Tk" for XFree86-OS/2 out-
     of-the-box, and link with DLLs for other useful libraries,
     which typically are compiled with "-Zmt -Zcrtdll".

  Calls to external programs
     Due to a popular demand the perl external program calling
     has been changed wrt Andreas Kaiser's port.  If perl needs
     to call an external program via shell, the f:/bin/sh.exe
     will be called, or whatever is the override, see

     Thus means that you need to get some copy of a sh.exe as
     well (I use one from pdksh). The path F:/bin above is set up
     automatically during the build to a correct value on the
     builder machine, but is overridable at runtime,

     Reasons: a consensus on "perl5-porters" was that perl should
     use one non-overridable shell per platform. The obvious
     choices for OS/2 are cmd.exe and sh.exe. Having perl build
     itself would be impossible with cmd.exe as a shell, thus I
     picked up "sh.exe". This assures almost 100% compatibility
     with the scripts coming from *nix. As an added benefit this

perl v5.12.5         Last change: 2012-11-03                   45

Perl Programmers Reference Guide                       PERLOS2(1)

     works as well under DOS if you use DOS-enabled port of pdksh
     (see "Prerequisites").

     Disadvantages: currently sh.exe of pdksh calls external
     programs via fork()/exec(), and there is no functioning
     exec() on OS/2. exec() is emulated by EMX by an asynchronous
     call while the caller waits for child completion (to pretend
     that the "pid" did not change). This means that 1 extra copy
     of sh.exe is made active via fork()/exec(), which may lead
     to some resources taken from the system (even if we do not
     count extra work needed for fork()ing).

     Note that this a lesser issue now when we do not spawn
     sh.exe unless needed (metachars found).

     One can always start cmd.exe explicitly via

       system 'cmd', '/c', 'mycmd', 'arg1', 'arg2', ...

     If you need to use cmd.exe, and do not want to hand-edit
     thousands of your scripts, the long-term solution proposed
     on p5-p is to have a directive

       use OS2::Cmd;

     which will override system(), exec(), "``", and
     "open(,'...|')". With current perl you may override only
     system(), readpipe() - the explicit version of "``", and
     maybe exec(). The code will substitute the one-argument call
     to system() by "CORE::system('cmd.exe', '/c', shift)".

     If you have some working code for "OS2::Cmd", please send it
     to me, I will include it into distribution. I have no need
     for such a module, so cannot test it.

     For the details of the current situation with calling
     external programs, see "2 (and DOS) programs under Perl" in
     Starting OS.  Set us mention a couple of features:

     o   External scripts may be called by their basename.  Perl
         will try the same extensions as when processing -S
         command-line switch.

     o   External scripts starting with "#!" or "extproc " will
         be executed directly, without calling the shell, by
         calling the program specified on the rest of the first

  Memory allocation
     Perl uses its own malloc() under OS/2 - interpreters are
     usually malloc-bound for speed, but perl is not, since its
     malloc is lightning-fast.  Perl-memory-usage-tuned

perl v5.12.5         Last change: 2012-11-03                   46

Perl Programmers Reference Guide                       PERLOS2(1)

     benchmarks show that Perl's malloc is 5 times quicker than
     EMX one.  I do not have convincing data about memory
     footprint, but a (pretty random) benchmark showed that
     Perl's one is 5% better.

     Combination of perl's malloc() and rigid DLL name resolution
     creates a special problem with library functions which
     expect their return value to be free()d by system's free().
     To facilitate extensions which need to call such functions,
     system memory-allocation functions are still available with
     the prefix "emx_" added. (Currently only DLL perl has this,
     it should propagate to perl_.exe shortly.)

     One can build perl with thread support enabled by providing
     "-D usethreads" option to Configure.  Currently OS/2 support
     of threads is very preliminary.

     Most notable problems:

         may have a race condition (but probably does not due to
         edge-triggered nature of OS/2 Event semaphores).  (Needs
         a reimplementation (in terms of chaining waiting
         threads, with the linked list stored in per-thread

         has a couple of static variables used in OS/2-specific
         functions.  (Need to be moved to per-thread structure,
         or serialized?)

     Note that these problems should not discourage
     experimenting, since they have a low probability of
     affecting small programs.

     This description is not updated often (since 5.6.1?), see
     ./os2/Changes (perlos2delta) for more info.

     Ilya Zakharevich,

     See attributes(5) for descriptions of the following

perl v5.12.5         Last change: 2012-11-03                   47

Perl Programmers Reference Guide                       PERLOS2(1)

     |Availability   | runtime/perl-512 |
     |Stability      | Uncommitted      |

     This software was built from source available at  The original
     community source was downloaded from

     Further information about this software can be found on the
     open source community website at

perl v5.12.5         Last change: 2012-11-03                   48