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Crontab Syntax Help

Hours of the day



3:03 pm on Oct 11, 2006 (gmt 0)

5+ Year Member

Hi, I am wondering if this is possible... I want to run a cron job for the first 1-12 hours of the day every 5 minutes, but also for the 21st to 24th hour of the day. It may sound stupid but it makes sense with what i'm doing. Does the below crontab look right? I know */5 updates every 5 minutes but does the 1-12,21-24 part look correct?

*/5 1-12,21-24 * * *


4:50 pm on Oct 11, 2006 (gmt 0)

10+ Year Member

It looks good except for one small issue. Midnight, in a cron time is 0. So the 1-12,21-24 should be 1-12,21-0.

As a side note: does anyone know if 21-12 would work instead of 1-12,21-0?


9:26 am on Oct 12, 2006 (gmt 0)

5+ Year Member

Both 1-12,21-0 or 21-12 don't work. After trying to save it, it says "bad hour: errors in crontab file, can't install".

It looks like the only way is the long way:
*/5 1,2,3,4,5,6,7,8,9,10,11,12,21,22,23,0 * * *

Doing it the long way there's no errors.


3:26 pm on Oct 12, 2006 (gmt 0)

WebmasterWorld Senior Member 10+ Year Member

What you want is:
*/5 0-12,21-23 * * *

That's the hour of midnight through the hour of noon, plus the hour of 9pm through the hour of 11pm, all inclusive.


2:54 am on Oct 13, 2006 (gmt 0)

5+ Year Member

The logic of */5 0-12,21-23 * * * looks right but I get the error message saying "bad hour: errors in crontab file, can't install".

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