Home / server / Questions / 237710
Accepted
webnoob
Asked: 2011-02-20 13:06:55 +0800 CST

Don't run cron job if already running

  • 772

I know this question has been asked already but I either didn't understand the answer or it didn't apply to me.

I have a php script that I am calling every 1 minute using CPanel to set up the Cron Job. The nature of the script means that it could overrun for just over the minute so I need to know how to stop the next one running if the first one hasn't completed.

I have a VPS running CENTOS 5.5 and have access to WHM and CPanel. I have never used Linux before (only just got the server yesterday) so I have no idea what I am doing and would appreciate some help if possible. If I need to provide more information please let me know (I don't know what info you would need at the moment).

Thanks.

linux php cron

4 Answers

  1. Use a bash script as your cron job

    cron.sh

    #!/bin/bash
$lockfile=/tmp/lock.file

if [ ! -e $lockfile ]; then
   touch $lockfile
   php /path/to/php/script.php
   rm $lockfile
else
   echo "script already running"
fi
    • 5
  2. Best Answer

    Please see Process Management. You will probably want to use a lock file. You can use flock for example.

    Why can't you let your jobs complete?

    Your questions says "I either didn't understand the answer or it didn't apply to me", but you don't say in what way. Please be more specific.

    • 4

  3. Docs: https://www.timkay.com/solo/

    solo is a very simple script (10 lines) that prevents a program from running more than one copy at a time. It is useful with cron to make sure that a job doesn't run before a previous one has finished.

    Example

    * * * * * solo -port=3801 ./job.pl blah blah
    • 1

  4. I am curious if implementing something with ps will solve the issue. Would simple ps -e | grep script_name.php | awk '{print $4}' be sufficient? It definitely will tell you if the script is running, no need to check if someone killed it beforehand. How creating and then removing a lock file is better/faster than this?

    I am not sure, just want to know pros and cons. Thanks

    • 0