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Can cron be modified via a script?

 
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Top Forums UNIX for Dummies Questions & Answers Can cron be modified via a script?
# 8  
Old 07-11-2014
You could also add/change an enabled record with:-
Code:
crontab -l | grep -v 1234123132 > /tmp/my_crontab
echo "0 * * * * /path/to/myscript.sh # 1234123132" >> /tmp/my_crontab
crontab /tmp/my_crontab

You can keep it in crontab, but disabled with:-
Code:
crontab -l | grep -v 1234123132 > /tmp/my_crontab
echo "#0 * * * * /path/to/myscript.sh # 1234123132" >> /tmp/my_crontab
crontab /tmp/my_crontab

This will, of course, put your new entry at the bottom. If you label all your entries and want to keep them in numerical order by the label suggested, try:-
Code:
crontab -l | grep -v 1234123132 > /tmp/my_crontab.1
echo "0 * * * * /path/to/myscript.sh # 1234123132" >> /tmp/my_crontab.1
sort -nbt "#" -k 2 /tmp/my_crontab.1 > my_crontab
crontab /tmp/my_crontab


Robin
# 9  
Old 07-12-2014
I've used Neo's two file solution to change a specific crontab action but rather than stopping cron, then restarting, I swap in a file that does nothing but return.
# 10  
Old 07-14-2014
Do you mean that you are replacing the /var/spool/cron/crontabs contents directly without restarting crond or leaving the definitions alone and are switching in/out your script for a dummy job when you don't want it run?

If it's the former, I would be concerned that cron will only read the files when it starts up unless it is signaled to do so.

Does your solution work? Can you confirm what you are doing for others who may find this thread in future.


Thanks,
Robin
# 11  
Old 07-18-2014
Left the crontab untouched and copied in a no process dummy when needed. This a long time ago.

Verified that it works with a testbed machine and 2 scripts interchanged at various times on SCO 5.0.5. Does require permission changes after the copy.
 
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