How to set a cron job to run every 3 hours [duplicate]

Question

This question already has answers here:

Running a cron job on Linux every six hours (7 answers)

Closed 6 years ago.

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.

Answer 1

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

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

Example

Answer 2

Change Minute parameter to 0.

You can set the cron for every three hours as:

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

Answer 3

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/