If you’re doing it in php, why not use php code:
In the running program:
define('PIDFILE', '/var/run/myfile.pid');
file_put_contents(PIDFILE, posix_getpid());
function removePidFile() {
unlink(PIDFILE);
}
register_shutdown_function('removePidFile');
Then, in the watchdog program, all you need to do is:
function isProcessRunning($pidFile="/var/run/myfile.pid") {
if (!file_exists($pidFile) || !is_file($pidFile)) return false;
$pid = file_get_contents($pidFile);
return posix_kill($pid, 0);
}
Basically, posix_kill has a special signal 0
that doesn’t actually send a signal to the process, but it does check to see if a signal can be sent (the process is actually running).
And yes, I do use this quite often when I need long running (or at least watchable) php processes. Typically I write init scripts to start the PHP program, and then have a cron watchdog to check hourly to see if it’s running (and if not restart it)…