How can I kill a Perl system call after a timeout?

Question

I\'ve got a Perl script I\'m using for running a file processing tool which is started using backticks. The problem is that occasionally the tool hangs and It needs to be killed

Answer 1

You need to set $SIG{'ALRM'} to a handler routine and then call the alarm function with the timeout value. Something like:

$SIG{'ALRM'} = handler;
foreach $file (@FILES) {
  alarm(10);
  $runResult = `mytool $file >> $file.log`;
  alarm(0);
}

sub handler {
  print "There was a timeout\n";
}

This should trigger the handler subroutine after 10 seconds. Setting alarm to 0 turns off the alarm.

Answer 2

I would probably not use `` for this. Instead I would open() the command with | so that it runs asynchronously. This will return the pid. Then you can do a nonblocking wait() in a loop with sleep that after a certain number of tries without success, issues a signal to the child pid.