Find running process id using php within crontab (RHEL4): crontab, pid, php, linux

Find running process id using php within crontab (RHEL4)

Asked by: poisa

I'm writing a php file that -via crontab- gets executed once every minute to send out mails. I'm not being able to device a method to prevent multiple instances of this program from running simultaneously. I only want ONE instance at a time.

My logic is:
1) Get all running processes using "ps auxwww" (plus some awk magic to get only pids for the specified file)
2) If there is more than one process running, meaning there is me, plus another process, exit gracefully.

The problem is that when I run this (see the code window below), I can ONLY see the process id of the currently running php file and none other. Even without filtering anything out, the output of ps auxw only has one process!

I'm guessing there is some sort of user permission thing going on. How can I go around this?

Thanks!

Context: Dedicated server running Red Hat Enterprise Linux 4 with PHP 5.2.9. I have root shell access.

<?php
// over simplified version
echo exec("ps auxw");
?>

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Sorry, I only know of the alternative I posted above. If you don't mind my asking, what's the problem if the script only runs a few lines before being told to continue or exit.

Here's a shell_exec class I found:
http://us.php.net/manual/en/function.shell-exec.php#59898

It's also been attached.

Sorry I can't help much more.

<?php
/**
 * @author     Ashraf M Kaabi
 * @name       Advance Linux Exec
 */
class exec {
    /**
     * Run Application in background
     *
     * @param     unknown_type $Command
     * @param     unknown_type $Priority
     * @return     PID
     */
    function background($Command, $Priority = 0){
       if($Priority)
           $PID = shell_exec("nohup nice -n $Priority $Command > /dev/null & echo $!");
       else
           $PID = shell_exec("nohup $Command > /dev/null & echo $!");
       return($PID);
   }
   /**
    * Check if the Application running !
    *
    * @param     unknown_type $PID
    * @return     boolen
    */
   function is_running($PID){
       exec("ps $PID", $ProcessState);
       return(count($ProcessState) >= 2);
   }
   /**
    * Kill Application PID
    *
    * @param  unknown_type $PID
    * @return boolen
    */
   function kill($PID){
       if(exec::is_running($PID)){
           exec("kill -KILL $PID");
           return true;
       }else return false;
   }
};
?>

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function processExists($process) { // Check if file is in process list exec("ps -ef|grep $process|grep -v grep", $pids); if (count($pids) >= 1) { $pids[0] = implode(" ", array_filter(explode(" ", $pids[0]))); $data = explode(" ", $pids[0]); if( isset($data[1]) ) { echo($file . " executing with pid " . $data[1]); exit(); } } echo($file . " not executing."); }

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Find running process id using php within crontab (RHEL4)

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crontab

pid

php

linux

PHP Scripting Language

Linux Administration

Red Hat Linux

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