How to set a cron job to run every 3 hours

Question

Is this the correct way for setting a cron job to run every 3 hours? After setting it this way, cron is executing the command every minute.

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http://unix.stackexchange.com/? – BenC Mar 19 '14 at 16:31 — BenC, Mar 19 '14 at 16:31

score 135 · Accepted Answer · edited Dec 20 '16 at 00:47

135

Change Minute to be 0. That's it :)

Note: you can check your "crons" in http://cronchecker.net/

edited Dec 20 '16 at 00:47

Aman Aggarwal

answered Mar 19 '14 at 16:11

jimm-cl

how can i set it to start at particular time as well ? for eg; every 3 hours starting from 12 pm. – Sidharth Ramesh Mar 06 '19 at 03:31

Aman Aggarwal · Answer 2 · 2016-11-11T11:10:40.210

42

Change Minute parameter to 0.

You can set the cron for every three hours as:

0 */3 * * * your command here ..

edited Nov 11 '16 at 11:10

answered Mar 25 '15 at 06:25

Aman Aggarwal

score 16 · Answer 3 · answered Oct 25 '15 at 09:08

16

The unix setup should be like the following:

 0 */3 * * * sh cron/update_old_citations.sh

good reference for how to set various settings in cron at: http://www.thegeekstuff.com/2011/07/cron-every-5-minutes/

answered Oct 25 '15 at 09:08

shacharsol

3 Answers3