Background running proces monitor

[Techidada]

Hi

I am running a background command and want to mointor output of that commands which generate some flag files. When it finish it should be stopped.

I tried this

open(MON, "$CMD > output.txt |") || die "Can't start the $COMCOMM";
while (<MON>) {
   opendir(DIR, $dir) or die " Can't open $dir";
    while ($file = readdir(DIR)) { 
      if ($file eq "still_running_flag") {
        print "$CMD is running...\n"; 
        sleep 10;
        next;
      }
    }
   }
 

The problem is it is not running in background.

Thanks

[KevinADC]

add $! to the die call and see if it helps determine why the command fails:

die "Can't start the $CDM : $!";

Edit: I possibly did not understand your question/problem. The process will not run in the background, it will run right then when you open/pipe to it, not sure what you are trying to do.