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Understanding cron scheduling command

 
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# 1  
Old 02-11-2009
Understanding cron scheduling command
Below are two cron entries. what is the difference beteeen writing 20 and */20? how is "20 * * * *" different from "*/20 * * * *"?

1) 20 * * * * find /tmp/ -name "*.log.*" ! -name "*.gz" -mmin +1440 -exec gzip '{}' \;

2) */20 * * * * find /tmp/ -name "*.tmp.*" ! -name "*.gz" -mmin +1440 -exec gzip '{}' \;

Thanks for your help...

Niks.
# 2  
Old 02-11-2009
Some (not all) *NIX cron implementation support the '*/n' notation - which means every 'n' period - in your case 'every 20 mins'.
# 3  
Old 02-11-2009
so, is 20 and */20 the same?
# 4  
Old 02-11-2009
Quote:
Originally Posted by niks
so, is 20 and */20 the same?
no, they are not
20 - once at 20min after a specified hour
*/20 - EVERY 20mins, i.e. at 0,20,40 mins of a specified hour
# 5  
Old 02-11-2009
I think i got it..
20 * * * * - means that the job would be executed at 20th minute every hour.
*/20 * * * * - means that the job would be executed every 20 minutes..

is my understanding correct?
# 6  
Old 02-11-2009
vgersh99, thanks for your quick response.
# 7  
Old 02-11-2009
Quote:
Originally Posted by niks
I think i got it..
20 * * * * - means that the job would be executed at 20th minute every hour.
*/20 * * * * - means that the job would be executed every 20 minutes..

is my understanding correct?
correcto mundo!
 
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