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Old 12-08-2015, 05:47 AM   #1
heathcliffz
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How to: Script run every 1 hour between 18h and 7h every day


Hey guys, how can I make a script run every 1 hour between 18h and 7h every day using cron?

Or... Is there other way without using cron on ubuntu based distros?

The script sends a mensage to the user saying that the PC will shutdown in 10 minutes, but the user can cancel and one hour later the script will ask again...

If you have any sugestions about how can I make this easier I would be happy to know!

Thanks!
 
Old 12-08-2015, 05:56 AM   #2
berndbausch
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Yes you can. See the man page for crontab http://man7.org/linux/man-pages/man5/crontab.5.html.
 
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Old 12-08-2015, 07:03 AM   #3
heathcliffz
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thanks

I let laziness aside and read the manual ...
from what I understand, I would look something like this:

Code:
0 18-7 * * * root echo "HI!"

or am I wrong?

Last edited by heathcliffz; 12-08-2015 at 07:14 AM.
 
Old 12-08-2015, 08:25 AM   #4
berndbausch
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Looks like you're right. The man page says "The specified range is inclusive. For example, 8-11 for an "hours" entry specifies execution at hours 8, 9, 10 and 11".

To console you, I spend 20% of my time reading manual pages. I can only remember the the stuff I use often.
 
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Old 12-08-2015, 08:55 AM   #5
rknichols
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Quote:
Originally Posted by heathcliffz View Post
thanks

I let laziness aside and read the manual ...
from what I understand, I would look something like this:

Code:
0 18-7 * * * root echo "HI!"
Cron may not understand that the range is supposed to wrap around midnight, and all versions of cron may not interpret that consistently. You should write that as
Code:
0 0-7,18-23 * * * root echo "HI!"
See https://www.google.com/search?as_q=cron+midnight+wrap

Also, while the format of that entry is correct for the system's /etc/crontab, where a user name is required for each entry, an individual user's crontab does not have that field:
Code:
0 0-7,18-23 * * * echo "HI!"
It's fortunate that you said you want to do this "every day." Doing it, e.g., "every day except Saturday night / Sunday morning" would be more complicated.

Last edited by rknichols; 12-08-2015 at 09:00 AM. Reason: Add format for individual user's crontab
 
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Old 12-08-2015, 09:02 AM   #6
heathcliffz
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Thumbs up

Quote:
To console you, I spend 20% of my time reading manual pages. I can only remember the the stuff I use often.
berndbausch,
I never read much about CRON because never needed something very specific, but now I read, I believe that I can think of something in the future...

Quote:
Cron may not understand that the range is supposed to wrap around midnight, and all versions of cron may not interpret that consistently.
rknichols,
Man, thank you! I had not thought about it!
 
  


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