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 run by cron every 5mn to check whether the process is still running.

Based on this page, I tried the following code, but it always returns True even if I call it with bogus data:

function processExists($file = false) {
    $exists= false;
    $file= $file ? $file : __FILE__;

    // Check if file is in process list
    exec("ps -C $file -o pid=", $pids);
    if (count($pids) > 1) {
    $exists = true;
    }
    return $exists;
}

#if(processExists("lighttpd"))
if(processExists("dummy"))
    print("Exists\n")
else
    print("Doesn't exist\n");

Next, I tried this code...

(exec("ps -A | grep -i 'lighttpd -D' | grep -v grep", $output);)
print $output;

... but don't get what I expect:

/tmp> ./mycron.phpcli 
Arrayroot:/tmp> 

FWIW, this script is run with the CLI version of PHP 5.2.5, and the OS is uClinux 2.6.19.3.

Thank you for any hint.

---

Edit: This seems to work fine

exec("ps aux | grep -i 'lighttpd -D' | grep -v grep", $pids);
if(empty($pids)) {
        print "Lighttpd not running!\n";
} else {
        print "Lighttpd OK\n";
}

Answer 1

The main problem is the if you run a php script, the exec command will be run as the web-servers user (www-data); this user can't see pid's from other users, unless you use "pidof"

<?php
//##########################################
// desc: Diese PHP Script zeig euch ob ein Prozess läuft oder nicht
// autor: seevenup
// version: 1.3
// info: Da das exec kommando als apache user (www-data) ausgefuert
//       wird, muss pidof benutzt werden da es prozesse von
//       anderen usern anzeigen kann
//##########################################

if (!function_exists('server_status')) {
        function server_status($string,$name) {
                $pid=exec("pidof $name");
                exec("ps -p $pid", $output);

                if (count($output) > 1) {
                        echo "$string: <font color='green'><b>RUNNING</b></font><br>";
                }
                else {
                        echo "$string: <font color='red'><b>DOWN</b></font><br>";
                }
        }
}

//Beispiel "Text zum anzeigen", "Prozess Name auf dem Server"
server_status("Running With Rifles","rwr_server");
server_status("Starbound","starbound_server");
server_status("Minecraft","minecarf");
?>

More information about the script here http://umbru.ch/?p=328

Answer 2

<?php

function check_if_process_is_running($process)
{
    exec("/bin/pidof $process",$response);
    if ($response)
    {
         return true;
    } else
    {
         return false;
    }
}

if (check_if_process_is_running("mysqld"))
{
      echo "MySQL is running";
} else
{
      echo "Mysql stopped";
}

?>

Answer 3

i have a function to get the pid of a process...

function getRunningPid($processName) {
    $pid = 0;
    $processes = array();
    $command = 'ps ax | grep '.$processName;
    exec($command, $processes);
    foreach ($processes as $processString) {
        $processArr = explode(' ', trim($processString));
            if (
            (intval($processArr[0]) != getmypid())&&
            (strpos($processString, 'grep '.$processName) === false)
        ) {
            $pid = intval($processArr[0]);
        }
    }
    return $pid;
}