SPUG:

[Jonathan Gardner]

On Monday 26 August 2002 04:40 pm, Creede Lambard wrote:
> I'd say, every time program A or program B runs, save its PID in a file
> somewhere (or database table, or whatever). Then, when you decide to
> shut down, go through the list in that file and kill all the pids in it.
>
> If you do this be sure to remove the PID entry when an instance of the
> program exits or you could cause yourself unnecessary work.
>

It's not much work to check to see if a PID stored in a file is valid. Try 
this:

	$pid = `cat $pidfile`;
	chomp $pid;
	if (kill 0, $pid) {
		# still running.
	} else {
		# dead - stale lockfile.
	}
	
There is a small chance that the child has been long dead and you have cycled 
through the available PIDs, and a different process is running as that PID, 
but what can you do about that?

-- 
Jonathan Gardner
jgardn at alumni.washington.edu

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