Posted by David Haynes on 03/03/06 04:52

s wrote:
> On Thu, 02 Mar 2006 15:18:43 -0500, Pol <Pol@nospam.com> wrote:
>
>> Can php scripts be initiated as a cron jobs running indefinately in a
>> loop performing a task?
>>
>> Any recommendations for writing a php script that will run as an unix
>> server process that will run indefinitely once it starts?
>>
>> If cron starts it every 10 minutes. How can I check if I my process is
>> running and then end if an instance is already running?
>
> One approach is to have your script write a pid file, and check for
> the presence of pid files from other instances of itself.
>
> There are a few different ways you can use the pid file; here is some
> code from a daemon that I have. This code writes a pid file for this
> instance, then goes looking to see what other pid files exist. If the
> create time of any given pid file is more than 12 hours old, the old
> process is killed.
>
> My goal here was to ensure that no running instance had been alive for
> more than 12 hours (I had my reasons). But you could easily rework the
> logic to, for example, prevent multiple instances from running at the
> same time.
>
> <?
> #Write a pid file
> touch('pidfiles/' . getmypid());
>
> #Look for other processes
> $dir = opendir('pidfiles') or die("Can't open PID directory\n");
> while(($filename = readdir($dir)) !== false){
> if(($filename == '.') || ($filename == '..')){
> continue;
> }
> $time = filectime('pidfiles/' . $filename);
> if($time < (time() - 43200)){
> #Kill off the old process
> `kill -9 $filename`;
> unlink('pidfiles/' . $filename);
> }
> }
>
> // Do your daemon stuff here...
>
> #Remove our own pid file
> unlink('pidfiles/' . getmypid());
> ?>
>
> If you use this approach, don't forget that your script should remove
> its own pid file if/when it finishes running cleanly, and it should
> remove the pid file of any other process that it kills off.
>
> hth
>
> --
> <s@guerril.la.ape> (to email, remove .ape)
> Apologies for the ad below.
> --
>
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flock a file in /tmp and fail if you don't get the flock.
Since the lock is handled by the kernel, it will die if the locking
process dies.

-david-

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