Catching errors from embedded script in parent script

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

Hello All,
I have written a code "auto_runner.pl" which invokes another script "embed.pl".
embed.pl script in turn opens an xterm and sends messages on this xterm. I want to catch the error thrown in this xterm. Zenity tags are used to highlight error when embed.pl comes across one.
Also that I have no control of changing the code in embed.pl since it is someone's else's code I am using...
Please suggest which direction should I proceed.
Looks clueless to me.

sub CIrc_check{
    my %SETUP=%{$_[0]};
    print "\033[33m Embed.pl invoked\033[0m\n";
    my $link=$SETUP{SVN};
    my $output_path=$SETUP{LOCATION_OF_OUTPUT};
    my $model_name=$SETUP{MODEL_NAME};
    $output_path=$output_path."/"."EMBED_RESULT";
    `mkdir $output_path`;
    chdir $output_path or die "Can't cd to $output_path : $!\n";
    `xterm -e embed.pl -link $link &`;
#When embed.pl strikes with an error in link or something it evaluated
+ it throws zenity tag sayin error in model name or so
}
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Re: Catching errors from embedded script in parent script by zentara (Cardinal) on Jun 09, 2012 at 10:06 UTC
You could use IPC::Open3, here is a basic example of collecting stdout separate from stderr. To test it's functioning, try entering "2 + 2" then try "2 / 0". #!/usr/bin/perl use warnings; use strict; use IPC::Open3; use IO::Select; my $pid = open3(\WRITE, \READ,\ERROR,"bc"); my $sel = new IO::Select(); $sel->add(\READ); $sel->add(\ERROR); my($error,$answer)=('',''); while(1){ print "Enter command\n"; chomp(my $query = <STDIN>); #send query to bash print WRITE "$query\n"; foreach my $h ($sel->can_read) { my $buf = ''; if ($h eq \ERROR) { sysread(ERROR,$buf,4096); if($buf){print "ERROR-> $buf\n"} } else { sysread(READ,$buf,4096); if($buf){print "$query = $buf\n"} } } } waitpid($pid, 1); # It is important to waitpid on your child process, # otherwise zombies could be created. [download] I'm not really a human, but I play one on earth. Old Perl Programmer Haiku ................... flash japh	[reply] [d/l]

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Re: Catching errors from embedded script in parent script
by zentara (Cardinal) on Jun 09, 2012 at 10:06 UTC

IPC::Open3

#!/usr/bin/perl
use warnings;
use strict;
use IPC::Open3;
use IO::Select;

my $pid = open3(\*WRITE, \*READ,\*ERROR,"bc");

my $sel = new IO::Select();

$sel->add(\*READ);
$sel->add(\*ERROR);

my($error,$answer)=('','');

while(1){

 print "Enter command\n";
 chomp(my $query = <STDIN>);
 
 #send query to bash
 print WRITE "$query\n";

 foreach my $h ($sel->can_read)
 {
   my $buf = '';
   if ($h eq \*ERROR)
   {
     sysread(ERROR,$buf,4096);
     if($buf){print "ERROR-> $buf\n"}
   }
   else
   {
     sysread(READ,$buf,4096);
     if($buf){print "$query = $buf\n"}
   }
 }
}

waitpid($pid, 1);
# It is important to waitpid on your child process,  
# otherwise zombies could be created.
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I'm not really a human, but I play one on earth.
Old Perl Programmer Haiku ................... flash japh

[reply]
[d/l]