Checking if process still running?

Question

As a way to build a poor-man\'s watchdog and make sure an application is restarted in case it crashes (until I figure out why), I need to write a PHP CLI script that will be

Answer 1

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)...