in reply to Re^3: How to stop printing the output of a command on screen when the command fails?
in thread How to stop printing the output of a command on screen when the command fails?

Hi, I am new to open3 and perldoc is too vague to understand I am trying a simple perforce command to run in open3.Basically I want to capture both STDOUT and STDERR aswell.I have tried various ways but none of them seem to be working.I am hoping someone will comment. 

foreach my $file (@changed_files)
{
    
#my $p4where_output=`p4 where $file > NUL: 2>&1`;#backticks option not
+ working,so commented out
#print "P4 where output:$p4where_output\n";

my $cmd = "p4 where $file";

local(*HIS_IN, *HIS_OUT, *HIS_ERR);

my $childpid = open3(*HIS_IN, *HIS_OUT, *HIS_ERR, p4 where $cmd);
print HIS_IN "stuff\n";
close(HIS_IN);            # Give end of file to kid.
my @outlines = <HIS_OUT>;    # Read till EOF.
my @errlines = <HIS_ERR>;    # XXX: block potential if massive
print "STDOUT:\n", @outlines, "\n";
print "STDERR:\n", @errlines, "\n";
print @errlines;
close HIS_OUT;
close HIS_ERR;
waitpid($childpid, 0);
if ($?) {
    print "That child exited with wait status of $?\n";
}

        if(@errlines eq 'file(s) not in client view')
        {
        push @changed_paths,"$file\n";
        }
}

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Re^5: How to stop printing the output of a command on screen when the command fails?
by zentara (Cardinal) on Dec 24, 2010 at 16:03 UTC
    You probably want to use IO::Select with the IPC3 filehandles, so you won't block. Look at this example, using the calculator program, bc. You can adapt your p4 to run this way. 
    #!/usr/bin/perl
use warnings;
use strict;
use IPC::Open3;
use IO::Select;

#interface to "bc" calculator
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 expression for bc, i.e. 2 + 2\n";
 chomp(my $query = <STDIN>);
 
 #send query to bc
 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]

      I really need help on this.Tried in a different way as below,am not able to store the STDERR output into any variable.The below program doesnt print anything.I have been working on this since last night,couldnt get a handle on this.Any help is truly appreciated.

      #!/usr/bin/perl -w 
use strict;  
use warnings;
use diagnostics;
#use diagnostics;
use IPC::Open3;
my @changed_paths;
my @changed_files=("//depot/perl/tools/scripts/files/data.c");
foreach my $file (@changed_files)
{

  my($wtr, $rdr, $err);
  use Symbol 'gensym'; $err = gensym;
  my $pid = open3($wtr, $rdr, $err,'p4 where $file');
  print "$err\n"; #prints as GLOB(0x183f108),why is it so?
  #waitpid( $pid, 0 ); //Why do we need this?Program never halts if th
+is is present
  my $child_exit_status = $? >> 8;
     if ($err eq 'file(s) not in client view') 
      {
          push @changed_paths,$file;
      }
      print @changed_paths;
}

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[reply]
[d/l]

        The single quotes in line 13 of your posted code. Is that really what you want - not interpolated? Perldoc shows it differently.

[reply]
[reply]

      Erasing this,posted twice

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