path: root/os2/README.OS2

		   Notes on the OS/2 Perl port

			Raymond Chen
			 (rjc@math.princeton.edu)

-1.  Background.

This port was based on the MS-DOS port by Diomidis Spinellis.

0.  Set-up.

First copy the files in the os2 directory into the parent
directory.  Also install the file msdos/dir.h in your include
directory.

1.  Compiling.

Perl has been compiled under MS-DOS using the Microsoft C compiler 
version 6.0.  Before compiling install dir.h as <sys/dir.h>.  You will 
need a Unix-like make program and something like yacc (e.g. bison).  I 
just ran yacc on my UNIX box and downloaded the resulting y.tab.[ch] 
files.  Compilation takes 45 minutes on a 16MHz 386 machine running
no jobs other than the compiler, so you will probably need something to 
do in the meantime.  Like, say, lunch.  (Compilation time does not
include formatting the manual.)  If you compile with optimization 
turned off, it takes about half as long.

The executable is 270k (perlsym.exe is 473k; if you compile
without optimization, the sizes are 329K/531K), and the top level 
directory needs 800K for sources, 550K for object code, and 800K for the 
executables, assuming you want to build both perl.exe and perlsym.exe
with full optimization.

The makefile will compile glob for you which you will need to place 
somewhere in your path so that perl globbing will work correctly.  All 
the tests were run, although some modifications were necessary because 
OS/2 isn't UNIX. The tests that failed failed because of limitations of 
the operating system and aren't the fault of the compiler.  a2p and s2p 
were not tested.  

In the eg directory you will find the syscalls.pl header file,
and a sample program that demonstrates some of the improvements
of the OS/2 version over the MS-DOS version and some of the
system calls.

2.  Using OS/2 Perl

The OS/2 version of perl has much of the functionality of the Unix 
version.  Here are some things that don't work:  sockets, password 
functions, [gs]et[eug]id, dbm functions, fork.  

One thing that doesn't work is "split" with no arguments.  Somehow,
yylval.arg is empty ...  [[ Wait, sorry, I fixed that. --rjc ]]

Care has been taken to implement the rest, although the implementation
might not be the best possible.  Here are short notes on the tricky 
bits:  

2.1.  In-place editing.

Files currently can be edited in-place provided you are creating a 
backup.  Considerable effort is made to ensure that a reasonable
name for the backup is selected, while still remaining within
the 8.3 contraints of the FAT filesystem.  (HPFS users have nothing
to worry about, since HPFS doesn't have the stupid 8.3 rule.)

The rules for how OS/2 perl combines your filename with the suffix
(the thing passed to "-i") are rather complicated, but the basic
idea is that the "obvious" name is chosen.

Here are the rules:

Style 0:  Append the suffix exactly as UNIX perl would do it.
          If the filesystem likes it, use it.  (HPFS will always
          swallow it.  FAT will rarely accept it.)

Style 1:  If the suffix begins with a '.', change the file extension
	  to whatever you supplied.  If the name matches the original 
	  name, use the fallback method.

Style 2:  If the suffix is a single character, not a '.', try to add the 
          suffix to the following places, using the first one that works.
              [1] Append to extension.  
              [2] Append to filename, 
              [3] Replace end of extension, 
              [4] Replace end of filename.
          If the name matches the original name, use the fallback method.

Style 3:  Any other case:  Ignore the suffix completely and use the
          fallback method.

Fallback method:  Change the extension to ".$$$".  If that matches the
          original name, then change the extension to ".~~~".

If filename is more than 1000 characters long, we die a horrible
death.  Sorry.

Examples, assuming style 0 failed.

suffix = ".bak" (style 1)
               foo.bar => foo.bak
               foo.bak => foo.$$$	(fallback)
               foo.$$$ => foo.~~~	(fallback)
               makefile => makefile.bak

suffix = "~" (style 2)
               foo.c => foo.c~
               foo.c~ => foo.c~~
               foo.c~~ => foo~.c~~
               foo~.c~~ => foo~~.c~~
               foo~~~~~.c~~ => foo~~~~~.$$$ (fallback)

               foo.pas => foo~.pas
               makefile => makefile.~
               longname.fil => longname.fi~
               longname.fi~ => longnam~.fi~
               longnam~.fi~ => longnam~.$$$
               
2.2.  Directory access.

Are implemented, but in order to support telldir() and seekdir(),
they operate by reading in the entire directory at opendir(),
then handing out pieces of it each time you do a readdir().

2.3.  Pipes and redirection.

Pipes and redirection are supported.  Although OS/2 does not 
terminate programs which try to write to closed pipes, perl will
kill them for you if you do it like this:

	open(I, "long-running-program|");
	... process a few lines ...
	close(I);	# discard the rest ...

The killing works like this:  We wait until the child program either
closes its stdout or tries to write to it.  If it writes to its stdout,
we kill it.  Otherwise, we cwait for it.  This is pretty much what UNIX
does by default.

All pipe commands are given to cmd.exe (or your COMSPEC) for execution as

	CMD /c your-command-line

so you can go ahead and load it up with any goofy things you want,
like 2>1 redirection, more pipes, && || etc.

The pipe() function is also supported, so you can go ahead and
make your own funky file descriptor connections before piping off
a process.  However, you have to mark the descriptor you are
retaining as NOINHERIT before spawning, else you are in deadlock city.
Unfortunately, there's no way to mark the handle as NOINHERIT yet.
It's on my wish list.

2.4.  Syscall and Ioctl

IOCtl is not supported because the API is very different from the
UNIX API.  Instead, IOCtl is supported as a syscall.  Here are
the syscalls I've written so far:

	$OS2_GetVersion = 0;
	$OS2_Shutdown = 1;
	$OS2_Beep = 2;
	$OS2_PhysicalDisk = 3;
	$OS2_Config = 4;
	$OS2_IOCtl = 5;
	$OS2_QCurDisk = 6;
	$OS2_SelectDisk = 7;
	$OS2_SetMaxFH = 8;
	$OS2_Sleep = 9;
	$OS2_StartSession = 10;
	$OS2_StopSession = 11;
	$OS2_SelectSession = 12;

The arguments you pass are handed off to OS/2 without interpretation,
and the return value is returned straight to you.  However, you don't
have to supply arguments for the ones whose descriptions are "must be 
zero"; perl will supply the mandatory zeros for you.

2.5.  Binary file access

Files are opened in text mode by default.  This means that CR LF pairs 
are translated to LF. If binary access is needed the `binarymode' 
function should be used.  There is currently no way to reverse the 
effect of the binary function.  If that is needed close and reopen the 
file.  

2.6.  Priority

The getpriority and setpriority functions are implemented, but since 
OS/2 priorities are different from UNIX priorities, the arguments aren't 
the same.  Basically, the arguments you pass are handed directly to 
OS/2. The only exception is the last argument to setpriority.  To make 
it easier to make delta priorities, if the priority class is 0xff, it 
is changed to 0.  That way, you can write

	setpriority(0,0,-2)

instead of

	setpriority(0,0,0xfe)

to decrease the delta by 2.

2.7.  Interpreter startup.

The effect of the Unix #!/bin/perl interpreter startup can be obtained 
under OS/2 by giving the script a .cmd extension and beginning the script 
with the line

	extproc C:\binp\perl.exe -S

You should provide the appropriate path to your executable, and
the -S option is necessary so that perl can find your script.

2.8.  The kill function.

UNIX and OS/2 have different ideas about the kill function.  I've
done a pretty feeble job of taking perl's UNIXish approach and
trying to jam it into the OS/2 way.  No doubt you'll find that
your kill()s aren't working.  My apologies in advance.

3.  Bug reports.

I don't normally have access to an OS/2 machine, so if you find
a bug, you can go ahead and tell me about it, but the odds that
I'd be able to fix it are slim.

4.  Wish list.

4.1.  OS/2.

Make ENOPIPE a fatal error.

Permit linking of files.  (Allegedly, they're working on this.)

Get a fork.

Make CMD.EXE pass through the return code of its child.

4.2 perl.

Provide a nice way to add new functions to perl without having
to understand the innards of perl.  Not being fluent in perl
innards hacking, I added my extra functions via syscall.

4.3. My port.

4.3.1.  In-place editing.

Make more idiot-proof.

Allow in-place editing without backup.  (How?)

4.3.2.  Spawning and piping.

Make popen() cleverer.  Currently, it blindly hands everything
off to CMD.EXE.  This wastes an exec if the command line didn't
have any shell metacharacters and if the program being run
is not a batch file.

Clever spawning is carried out by do_spawn.  We should try
to make popen() do much of the same sort of preprocessing
as do_spawn does (which means, of course, that we probably
should yank out code to be dished off into a subroutine).

In do_spawn(), use DosExecPgm instead of spawnl in order to get more 
precise reasons why the child terminated (RESULTCODES).


				July 1990

				Raymond Chen <rjc@math.princeton.edu>
				1817 Oxford St. Apt 6
				Berkeley, CA 94709-1828 USA