Perl 5 version 8.0 documentation



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


One can read this document in the following formats:

  1. man perlos2
  2. view perl perlos2
  3. explorer perlos2.html
  4. info perlos2

to list some (not all may be available simultaneously), or it may be read as is: either as README.os2, or pod/perlos2.pod.

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 xview.

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 limitations:

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

  • 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.

  • 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 items.

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, beware!

    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

    2. [EMX+GCC Development]

    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

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

  • 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 PERL_SH_DIR).

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


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

  1. perl arg1 arg2 arg3

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

  1. 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:

  1. extproc perl -S -my_opts

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

  1. 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

  1. 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 line).

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

  1. view perl perlrun
  2. man perlrun
  3. view cmdref extproc
  4. 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), `` (see I/O Operators in perlop), and open pipe (see open) are for. (Avoid exec() (see exec) 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 PERL_SH_DIR).

The cases when the shell is used are:

  • One-argument system() (see system), exec() (see exec) with redirection or shell meta-characters;

  • Pipe-open (see open) with the command which contains redirection or shell meta-characters;

  • Backticks `` (see I/O Operators in perlop) with the command which contains redirection or shell meta-characters;

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

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

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

  • For globbing (see glob, I/O Operators in perlop) (obsolete? Perl uses builtin globbing nowadays...).

  • 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 set).

    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 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

    • Did you run your programs with -w switch? See 2 (and DOS) programs under Perl in Starting OS.

    • 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 program.

    • 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 "correctly".

    `` 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.

    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;

    1. find "pattern" file
    2. 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

    1. system 'cmd', '/c', 'find "pattern" file';
    2. `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 away.

    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

    1. emxrev

    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:


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


      see PERL_BADFREE.


      This file resides somewhere deep in the location you installed your perl library, find it out by

      1. 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)
      1. unzip *.exe *.ico -d f:/emx.add/bin
      2. unzip *.dll -d f:/emx.add/dll

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

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

      (have the directory on PATH);

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

      (have the directory on PATH);

    • Main Perl library
      1. 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
      1. unzip -d f:/perllib/lib/site_perl/5.8.3/

      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
      1. unzip -d f:/perllib/lib

      Same remark as for

    • Manpages for Perl and utilities
      1. 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
      1. 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
      1. 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: info , LaTeX , Acrobat , FrameMaker and so on. [Use programs such as pod2latex etc.]

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

      This directory should better be on BOOKSHELF .

    • Pdksh
      1. 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

    1. 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 executables/DLLs.

    Accessing documentation

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

    OS/2 .INF file

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

    1. view perl
    2. view perl perlfunc
    3. view perl less
    4. view perl ExtUtils::MakeMaker

    (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

    1. pod2ipf > perl.ipf

    in /perllib/lib/pod directory, then

    1. 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

    1. perldoc perlfunc
    2. perldoc less
    3. 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:

    1. man perlfunc
    2. man 3 less
    3. man ExtUtils.MakeMaker

    to access documentation for different components of Perl. Start with

    1. 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

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

    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

    1. cd f:/perllib/lib/pod
    2. pod2html

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

    1. 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. There is an alternative (but maybe older) view on

    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

    1. gnupatch -p0 < os2\diff.configure
    2. sh Configure -des -D prefix=f:/perllib
    3. make
    4. make test
    5. make install
    6. make aout_test
    7. 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

    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

    1. find --version
    2. 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.

    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

    1. 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 typing

    1. link386

    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

    1. 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.

    Change to the directory of extraction.

    Application of the patches

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

    1. 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 anywhere.


    1. 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 PERLLIB_PREFIX , see PERLLIB_PREFIX.

    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.


    1. make

    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

    1. 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 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 sighandlers.

      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

    1. perl t/harness

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

    1. Failed Test Status Wstat Total Fail Failed List of failed
    2. ------------------------------------------------------------
    3. io/pipe.t 12 1 8.33% 9
    4. 7 tests skipped, plus 56 subtests skipped.
    5. Failed 1/195 test scripts, 99.49% okay. 1/6542 subtests failed, 99.98% okay.

    The reasons for most important skipped tests are:

    • op/fs.t
    • Checks atime and mtime of stat() - unfortunately, HPFS provides only 2sec time granularity (for compatibility with FAT?).

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

    • op/stat.t

      Checks stat(). Tests:

    • 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 now.


    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 LIBPATH.


    1. 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

    1. make perl_

    test and install by

    1. make aout_test
    2. 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

    1. make perl_dll


    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.

    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

    1. extproc /bin/bash -x -c

    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

    1. 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 PERL_SH_DIR).

    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:

    • File::Copy::syscopy

      used by File::Copy::copy , see File::Copy.

    • DynaLoader::mod2fname

      used by DynaLoader for DLL name mangling.

    • Cwd::current_drive()

      Self explanatory.

    • Cwd::sys_chdir(name)

      leaves drive as it is.

    • Cwd::change_drive(name)

      chanes the "current" drive.

    • Cwd::sys_is_absolute(name)

      means has drive letter and is_rooted.

    • Cwd::sys_is_rooted(name)

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

    • Cwd::sys_is_relative(name)

      means changes with current dir.

    • Cwd::sys_cwd(name)

      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.

    • Cwd::extLibpath([type])

      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 .

    • OS2::Error(do_harderror,do_exception)

      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 exceptions.

      I know of no way to find out the state of popups before the first call to this function.

    • OS2::Errors2Drive(drive)

      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 requested.

      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 function.

    • OS2::SysInfo()

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

    • OS2::BootDrive()

      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 details.

    • OS2::Serve_Messages(force)

      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.

      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 present.

      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.

    • OS2::_control87(new,mask)

      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.

    • OS2::get_control87()

      gets the coprocessor control word as an integer.

    • OS2::set_control87_em(new=MCW_EM,mask=MCW_EM)

      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:

    • $OS2::emx_rev

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

    • $OS2::emx_env

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

    • $OS2::os_ver

      a number OS_MAJOR + 0.001 * OS_MINOR .

    • $OS2::is_aout

      true if the Perl library was compiled in AOUT format.

    • $OS2::can_fork

      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}.

    • $OS2::nsyserror

      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 not.)


    • 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 .

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

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

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

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

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

      • waitpid(3):

        1. WUNTRACED
        2. Not implemented.
        3. waitpid() is not implemented for negative values of PID.

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

    • See Text-mode filehandles.

    • 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.

    • 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 predictable.

      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 death.

      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 ways:

    • popen

      my_popen uses sh.exe if shell is required, cf. PERL_SH_DIR.

    • tmpnam

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

    • tmpfile

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

    • ctermid

      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 USE_PERL_FLOCK=0 .

    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:

    • HAB

      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

      1. extern int Perl_hab_GET(void);


    • HMQ

      There are two cases:

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

      • 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 basis.

    • * 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 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 are

      • CheckOSError(expr)

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

      • CheckWinError(expr)

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

      • SaveWinError(expr)

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

      • SaveCroakWinError(expr,die,name1,name2)

        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.

      • WinError_2_Perl_rc

        Sets Perl_rc to the return value of WinGetLastError().

      • FillWinError

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

      • FillOSError(rc)

        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 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:

      1. CallORD(), DeclFuncByORD(), DeclVoidFuncByORD(),
      2. DeclOSFuncByORD(), DeclWinFuncByORD(), AssignFuncPByORD(),
      3. DeclWinFuncByORD_CACHE(), DeclWinFuncByORD_CACHE_survive(),
      4. DeclWinFuncByORD_CACHE_resetError_survive(),
      5. DeclWinFunc_CACHE(), DeclWinFunc_CACHE_resetError(),
      6. 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 functions.

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

    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 distribution:


    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 yourself.


    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 application.

    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 application.

    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 debugger).

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

    1. 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!

    1. open P, 'pm_prog args 2>&1 |' or die;
    2. 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 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.

    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:

    • explicit fork() in the script,

    • open FH, "|-"

    • open FH, "-|" , in other words, opening pipes to itself.

    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

    1. path1;path2


    1. 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

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

    This will cause Perl with the prebuilt @INC of

    1. f:/perllib/lib/5.00553/os2
    2. f:/perllib/lib/5.00553
    3. f:/perllib/lib/site_perl/5.00553/os2
    4. f:/perllib/lib/site_perl/5.00553
    5. .

    to use the following @INC:

    1. h:/opt/gnu/5.00553/os2
    2. h:/opt/gnu/5.00553
    3. h:/opt/gnu/site_perl/5.00553/os2
    4. h:/opt/gnu/site_perl/5.00553
    5. .


    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 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 files.


    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, getpriority" .

    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

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

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

    • 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" DLLs).

    • 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 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:

    • 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 executable.

    • 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.)

    REMARK. LIBPATHSTRICT , BEGINLIBPATH and ENDLIBPATH 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.

    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

    2. DESCRIPTION ' Perl module for 5.00553 -> Perl 5.6.1 forwarder'
    5. EXPORTS

    modifying the versions/names as needed. Run

    1. 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).

    1. cat perl5shim.def-leader lst >perl5shim.def
    2. 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 PERL_SH_DIR.

    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 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

    1. 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

    1. 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:

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

    • 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 line.

    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 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 structure?)?)

    • os2.c

      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 was not updated since 5.6.1, see os2/Changes for more info.


    Ilya Zakharevich,