IPC problem

gyre007 has asked for the wisdom of the Perl Monks concerning the following question:

Hi all... ve been doing some IPC scripts....not very succesfully.. Let me introduce it to you:

#!/usr/bin/perl

use IPC::Open3;
use POSIX qw( :sys_wait_h );

my $pid;
my $cmd = "extern.pl";
my $cmd2 = "extern2.pl";
my $exit_code = 0;
my $exit_code2 = 0;
my $help = 0;
my $help2 = 0;

$pid = open3(*MMRET_IN, *MMRET_OUT, *MMRET_ERR, $cmd);
print "Process spawned with PID = $pid \n";
$help = waitpid($pid,WNOHANG);
print "HELP_VALUE is $help\n";
$exit_code = $? >> 8;
print "ExitCODE is $exit_code \n";

$pid2 = open3(*MMRET_IN2, *MMRET_OUT2, *MMRET_ERR2, $cmd2);
print "Process spawned with PID = $pid2 \n";
$help2 = waitpid($pid2,WNOHANG);
print "HELP_VALUE is $help2\n";
$exit_code2 = $? >> 8;
print "ExitCODE is $exit_code2 \n";
[download]

"extern.pl" and "extern2.pl" are scripts that I want to execute from the main script - as child processes... extern.pl exits with the value "2" and extern2.pl exits with the value "1" I would expect that in $exit_code2 would be stored the exit value from the extern2.pl - "1" Problem is that it does not happen... In variable $? stays the exit value of script extern.pl and doesn not get overwritten byt the exit value of extern2.pl script. Does anyone know how can I get the exit value of second executed scrip "extern2.pl"? Thanks a LOT gyre

Comment on IPC problem Download Code

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Re: IPC problem by almut (Canon) on Oct 18, 2007 at 13:25 UTC
I think you don't want `WNOHANG` here... At least, with `waitpid($pid,0)` it does what I'd expect it to do. Sample output: `Process spawned with PID = 24247 HELP_VALUE is 24247 ExitCODE is 2 Process spawned with PID = 24248 HELP_VALUE is 24248 ExitCODE is 1` [download]	[reply] [d/l] [select]
Re^2: IPC problem by gyre007 (Novice) on Oct 18, 2007 at 13:32 UTC
Maybe it is a bug of Perl...because I changed the script as you suggested and still get the same result :( `Process spawned with PID = 16921 HELP_VALUE is 16921 ExitCODE is 2 Process spawned with PID = 16922 HELP_VALUE is 16922 ExitCODE is 2` [download]	[reply] [d/l]
Re^3: IPC problem by almut (Canon) on Oct 18, 2007 at 13:52 UTC
Hm, maybe. What version of Perl / IPC::Open3? What platform? I can't reproduce the problem here (5.8.8 / 1.0106, Linux), so we'll have to wait until someone else can... You have changed `waitpid($pid2,0)` too, have you? (which is what I implied, but didn't explicitly say) (the problem with `WNOHANG` is that the process might not yet have terminated at that point, so you wouldn't get a valid return code).	[reply] [d/l] [select]
Re^4: IPC problem by gyre007 (Novice) on Oct 18, 2007 at 13:57 UTC
Re^4: IPC problem by gyre007 (Novice) on Oct 18, 2007 at 14:02 UTC
Re^5: IPC problem by almut (Canon) on Oct 18, 2007 at 14:22 UTC
Re^3: IPC problem by gyre007 (Novice) on Oct 18, 2007 at 13:52 UTC
And maybe it's the problem of my scripts "external.pl" and "external2.pl" here they are: external.pl: `#!/usr/bin/perl my $i =0; while($i<=1000000){ if($i == 800){ exit 2; } $i++; }` [download] external2.pl: `#!/usr/bin/perl my $i =0; while($i<=1000000){ if($i == 900){ exit 1; } $i++; }` [download] Or I don't know what can cause these problems then...	[reply] [d/l] [select]