What's the best way to make sure only one instance of a Perl program is running?

Question

There are several ways to do this, but I\'m not sure which one of them is the best.

Here\'s what I can think of:

• Look for the process using pgrep.

Answer 1

Do the old PID file trick.

• start process
• see if there is a file called "myprog.PID"
• check for existence of running proc. with matching PID using kill 0, $pid
• if prog name of PID proc. matches, complain loudly and exit
• if not, clean up stale "myprog.PID"
• create a file called "myprog.PID" and then continue

HTH

cheers,

Rob