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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 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).

Note that if you have lynx.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 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:

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 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.

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   [EMX+GCC Development]

The runtime component should have the name

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

emx perl_.exe -de 0

will work as well.)


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.


Perl does not care about file systems, but to install the whole perl library 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.


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

perl arg1 arg2 arg3

If you want to specify perl options -my_opts to the perl itself (as opposed to 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 line").

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

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 enables a search 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 "PERL_SH_DIR").

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-characters;

  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-characters;

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

  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;

  7. For globbing (see "glob" in perlfunc, "I/O Operators" in perlop).

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 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).

If starting scripts directly, Perl will use 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.

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 as as simple as that: since blah. and blah denote the same file, to start an executable residing in file n:/bin/blah (no extension) give an argument n:/bin/blah. (dot appended) to system().

Perl will correctly start PM programs from VIO (=text-mode) Perl process; the opposite is not true: when you start a non-PM program from a PM Perl process, it 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

I cannot embed perl into my program, or use perl.dll from my program.

Is your program EMX-compiled with -Zmt -Zcrtdll?

If not, 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?

I had reports it does not work. Somebody would need to fix it.

`` 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

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. In fact find.exe cannot be started at all using C library API only. Otherwise the following command-lines would be equivalent:

find "pattern" file
find pattern file


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


A folder is created on your desktop which contains some useful objects.

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".



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.

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:

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

(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/5.8.3/

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.

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: info, LaTeX, Acrobat, FrameMaker and so on.

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 (file globbing - if done via shell - may break).

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"), one may get better results by 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

view perl
view perl perlfunc
view perl less
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

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

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 pod2info from CPAN, or, alternately, prebuilt info pages.

.PDF files

for Acrobat are available on CPAN (for slightly old 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

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 * is a not-very-meaningful hex checksum), and run

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

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 this from are

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:

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


if you use something like CMD.EXE or latest versions of 4os2.exe.

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


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.

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.

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


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


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.



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).

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

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:


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.


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.


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.


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.

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


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 can lock the system before Warp3 fixpak22.


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. 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

If /bin/bash is not found, and appending of executable extensions to /bin/bash does not help either, then Perl looks for an executable bash 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 "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 different type than the current session, it will start the new process in a separate session of necessary type. Call via OS2::Process to disable this magic.

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.

Prebuilt methods:


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


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 true, works with END_LIBPATH, otherwise with BEGIN_LIBPATH.

Cwd::extLibpath_set( path [, type ] )

Set current value of extended library search path. If type is present and true, works with END_LIBPATH, 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 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.


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.


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 details.


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.


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.

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

Prebuilt variables:


same as _emx_rev of EMX, a string similar to 0.9c.


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


a number OS_MAJOR + 0.001 * OS_MINOR.



Perl modifies some standard C library calls in the following ways:


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


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.


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.


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 HABs and HMQs. 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:

  • 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.

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

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 detached (run help detach for more info). Very useful for extensions which use PM, like Perl/Tk or OpenGL.


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: all the references to external functions are resolved at the compile time; 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 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:

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 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.


Specific for EMX port. Used as storage place for temporary files.


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


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

DLL name mangling

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


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

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:

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. Needs a reimplementation (in terms of chaining waiting threads, with the linked list stored in per-thread structure?).


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.


Ilya Zakharevich,



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