I have a script that runs an external command. If the command fails to respond within 20 seconds, I kill it off and proceed to the rest of the script. However, when I have to "kill" the process, it is leaving a zombie child process.

Since this command can be run hundreds to thousands of times in a given period, the zombie processes add up and eventually the system will return with a "Resources not available, unable to fork," and eventually the script will die.

Here is the code in question (which I found using sites like this). Is there a better way to do this, or is my code just screwy.

eval
{
     local $SIG{ALRM} = sub { die "alarm\n" };
     alarm 20;
     $CHILD = fork();
     if( $CHILD == 0 )
     {
          exec( "my external command" );
     }
     waitpid( $CHILD, 0 );
     alarm 0;
};
if( $@ )
{
     die unless $@ eq "alarm\n";
     kill 9, $CHILD
}

[download]

What I need is a way to execute a external command via perl. Have it timout after a certain period if it fails to respond, and then kill the child process if it hits the timeout period.

This is on OS X 10.6 with the latest version of Perl

EDIT: By just simply adding another waitpid after the kill command (as suggested), the zombies are gone. Not sure why I never tried that before! Thanks for the help!

In reply to exec creating zombie processes by jaiieq

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