Difference between these cron commands


 
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# 1  
Old 05-14-2012
Difference between these cron commands

Hi all I want to make sure I was understanding this correctly

if a cron job command was

Code:
* */20 * * * command

does that mean this command will run every 20 hours?

also what is the difference between the following two?

Code:
0,20,40 * * * * command

Code:
20 * * * * command

I believe the first one runs the command at 0, 20 and 40 minutes while the other runs every 20 minutes. . but I am not sure. ThanksSmilie
# 2  
Old 05-14-2012
sorry bad post

Last edited by 47shailesh; 05-14-2012 at 01:27 PM.. Reason: messed up with minutes and hour fields sorry
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# 3  
Old 05-14-2012
First cron: Hourly except at 20:00 . What did you intend? I'm assuming that this certain editions of Linux because the syntax is invalid in unix.

Second cron: every 20 mins (On the hour; twenty minutes past the hour; and forty minutes past the hour).

Third cron: At 20 minutes past every hour.

Last edited by methyl; 05-14-2012 at 01:34 PM.. Reason: update /20
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# 4  
Old 05-14-2012
Quote:
Originally Posted by methyl
First cron: Hourly except at 20:00 . What did you intend? I'm assuming that this certain editions of Linux because the syntax is invalid in unix.

Second cron: every 20 mins (On the hour; twenty minutes past the hour; and forty minutes past the hour).

Third cron: At 20 minutes past every hour.
I'm just learning syntax differences. Thank you for your reply I appreciate it!
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