Will Cron Job Interrupt Previous Process?

Question

I have a cron job which works every minute like below

*/1 * * * *

My script sometimes spends more than 1 minute to finish itself. My question is,

will next cron job interrupt current processing one?

For better understanding;

First script starts at 07.00 and ends 07.03 (3 minutes) Will cron intterrupt above process and start new one from start at 07.01?

No, it won't do that. You should take care of that by yourself if it's needed. — Alma Do, Jun 24 '15 at 13:42

score 3 · Answer 1 · answered Jun 24 '15 at 13:42

3

Cron will start a new process each time. Once cron has started a process it then leaves it to itself and has no further control over it.

If you need your process to wait for existing ones to finish you'll need to code that into your process yourself.

answered Jun 24 '15 at 13:42

Eborbob

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Hmm thanks for your answer. Is there any documentation or source about this issue? – hakki Jun 25 '15 at 11:26
There are different cron utilities out there - e.g. Ubuntu comes with vixiecron (http://manpages.ubuntu.com/manpages/vivid/man8/cron.8.html). `cron then wakes up every minute, examining all stored crontabs, checking each command to see if it should be run in the current minute.` If the way cron works is an issue for you you'll need to explain what functionality you are after and then someone might be able to assist. – Eborbob Jun 25 '15 at 11:51

score 0 · Answer 2 · answered Feb 02 '22 at 22:10

Try using or look into flock();

What this does is, locks a file, a simple file, so, you can create a simple empty file and usa a condition to see if its locked or not, if is locked then terminate the process, if is not locked then continue with process.

try something like this:

$f = fopen('./tmp/lock.txt', 'w') or die ('path to file doesn't exist');
$lock = flock($f, LOCK_EX | LOCK_NB) or die ('lock.txt is locked, is being used');
echo "lock is free";
//continue with code here

if you are using this in a script that is being triggered by cron, be sure to use LOCK_NB, is you don´t use it, it will indicate to use the wait() command until lock.txt is unlocked.

take a look at this post

https://stackoverflow.com/a/10552054/15285033

Will Cron Job Interrupt Previous Process?

2 Answers2