Linux – Don’t run cron job if already running

cronlinuxPHP

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.

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.

Related Solutions

Cron Job – How to Run a Cron Job Manually and Immediately

Here's what I did, and it seems to work in this situation. At least, it shows me an error, whereas running from the command line as the user doesn't show the error.

Step 1: I put this line temporarily in the user's crontab:

* * * * *   /usr/bin/env > /home/username/tmp/cron-env

then took it out once the file was written.

Step 2: Made myself a little run-as-cron bash script containing:

#!/bin/bash
/usr/bin/env -i $(cat /home/username/tmp/cron-env) "$@"

So then, as the user in question, I was able to

run-as-cron /the/problematic/script --with arguments --and parameters

This solution could obviously be expanded to make use of sudo or such for more flexibility.

Hope this helps others.

Linux – Where is this cron job running from

On my Debian system, /var/log/syslog contains an entry for each cron job which is executed …

Jan 17 20:10:01 machine1 /USR/SBIN/CRON[1545]: (convict) CMD (fetchmail -s >/dev/null 2>&1)
Jan 17 20:17:01 machine1 /USR/SBIN/CRON[1800]: (root) CMD (   cd / && run-parts --report /etc/cron.hourly)
Jan 17 20:20:01 machine1 /USR/SBIN/CRON[1914]: (convict) CMD (fetchmail -s >/dev/null 2>&1)

If your job is being executed by cron, you should find a reference to it in /var/log/syslog.

Best Answer

Related Solutions

Cron Job – How to Run a Cron Job Manually and Immediately

Linux – Where is this cron job running from

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