I'm writing scripts which need to execute some other programs, and look at the stdout and stderr from said calls. My scripts, in turn, are to be called by a 3rd party, closed source program.

I've been using IPC::Open3 for this, and things work great when run from the commandline. But when invoked by the 3rd party program, the call to open3 fails with the following messsage: open3: Can't call method "close" on an undefined value at c:/apps/perl/lib/IPC/Open3.pm line 368.

I whipped up a small test script to illustrate the problem. The 3rd party program doesn't display stdout or stderr, hence why I'm writing everything to files. Also, the "#------#" lines are just to show where the script starts and ends in this post, and are not present in the script

#------# Begin code for test_open3.pl 
#!c:/apps/perl/bin/perl

use IPC::Open3 qw( open3 );
use strict;
use warnings;
$| = 1;

open DBG, ">debug2.log" or die $!;
eval
{
        my @pids;
        my @cmd1 = ( 'c:/Program Files/TortoiseSVN/bin/svn.exe', '--ve
+rsion', '--

quiet');
        my $nul = $^O eq 'MSWin32' ? 'nul' : '/dev/null';

        open(CHILD_STDERR, '>', 'error.txt') or die "Could not open CH
+ILD_STDERR for 

writing ($!)";
        open(CHILD_STDOUT, '>', 'out.txt') or die "Could not open CHIL
+D_STDOUT for 

writing ($!)";

        push @pids, open3(undef, '>&CHILD_STDOUT', '>&CHILD_STDERR', @
+cmd1);
    waitpid($_, 0) for @pids;
    print "Child exited with value ", $? >> 8, "\n";
        #close(CHILD_STDIN) or die "Could not clost STDIN ($!)";

    close CHILD_STDOUT or die "Could not close STDOUT";
    open(CHILD_STDOUT, '<', 'out.txt') or die "Could not open CHILD_ST
+DOUT for reading 

($!)";
    my @out = <CHILD_STDOUT>;
    close CHILD_STDOUT or die "Could not close STDOUT ($!)";

    close CHILD_STDERR or die "Could not close STDERR";
    open(CHILD_STDERR, '<', 'err.txt') or die "Could not open CHILD_ST
+DERR for reading 

($!)";
    my @err = <CHILD_STDERR>;
    close CHILD_STDERR or die "Could not close STDERR ($!)";

    print "----OUT----\n", join("\n", @out), "----OUT----\n";
    print "----ERR----\n", join("\n", @err), "----ERR----\n";
    print DBG "Done!\n";
};
if ($@)
{
    print DBG $@;
    close DBG;
    exit 1;
}

close DBG;
#------#
[download]

The above code yields open3: Can't call method "close" on an undefined value at c:/apps/perl/lib/IPC/Open3.pm line 368. inside the debug2.log file.

I tried a slightly different approach with this test script:

#------# begin code for test9.pl
#!c:/apps/perl/bin/perl

use IPC::Open3 qw( open3 );
use strict;
use warnings;

open DBG, ">debug2.log" or die $!;
eval
{
    my @cmd1 = ( 'c:/Program Files/TortoiseSVN/bin/svn.exe', '--versio
+n', '--quiet');
    print "Running ", join(" ", map { "'$_'" } @cmd1), "\n";
    open my $old_stdout, '>&', STDOUT or die "Couldn't dup stdout! ($!
+)";
    open my $old_stderr, '>&', STDERR or die "Couldn't dup stderr! ($!
+)";
    open STDOUT, '>', 'out.txt' or die "Couldn't redirect stdout to fi
+le! ($!)";
    open STDERR, '>', 'err.txt' or die "Couldn't redirect stderr to fi
+le! ($!)";
    system(@cmd1);


    close STDOUT;
    close STDERR;
    open STDOUT, '>&', $old_stdout or die "Could not re-connect to std
+out! ($!)";
    open STDERR, '>&', $old_stderr or die "Could not re-connect to std
+err! ($!)";
    open FH, '<', 'out.txt' or die "Could not open out.txt! ($!)";
    open FH2, '<', 'err.txt' or die "Could not open err.txt! ($!)";
    my ($out, $err);
    {
        local $/;
        $out = <FH>;
        $err = <FH2>;
    }
    close FH;
    close FH2;

    print "----OUT----\n", $out, "\n----OUT----\n";
    print "----ERR----\n", $err, "\n----ERR----\n";
        #print join("\n", @err), "\n";
};
if ($@) { print DBG $@; exit 1; }

close DBG;
#------#
[download]

...and that also works just fine under the commandline, but bombs when invoked by the 3rd party program. This time, the error message in debug2.log is: Couldn't dup stdout! (Permission denied) at d:/users/jdoe/test9.pl line 12.

I'm trying hard to avoid invoking the shell. The scripts need to run under a wide variety of systems: ActiveState Perl, Cygwin Perl, actual Unix systems, ActiveState Perl running under Cygwin, etc. This makes using backquotes a real pain since it's hard to know what shell will be executed and thus what rules to use when shell escaping a command.

UPDATE: Forgot to actually ask the proper question: The 3rd party program seems to be doing something funky to stdout (and maybe stderr and/or stdin) which is causing open3 to bomb. Does anyone have any suggestions on how to cope with this, or a different way to tackle the problem without invoking the shell? I'd also appreciate any insight as to what could be going on, even if you don't have suggestions for a solution. I couldn't find anything on google or perlmonks' search, though maybe my search-fu is weak.

UPDATE 2: Running perl --version yields:

This is perl, v5.8.9 built for MSWin32-x86-multi-thread
(with 13 registered patches, see perl -V for more detail)

Copyright 1987-2008, Larry Wall

Binary build 828 [294165] provided by ActiveState http://www.ActiveSta
+te.com
Built Dec  8 2010 16:51:11

Perl may be copied only under the terms of either the Artistic License
+ or the
GNU General Public License, which may be found in the Perl 5 source ki
+t.

Complete documentation for Perl, including FAQ lists, should be found 
+on
this system using "man perl" or "perldoc perl".  If you have access to
+ the
Internet, point your browser at http://www.perl.org/, the Perl Home Pa
+ge.
[download]