http://www.adminschoice.com/docs/crontab.htm
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CRONTAB (6 fields)
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FILES:
LINUX
1) /etc/cron.allow
2) /etc/cron.deny
Fields:-
Minute 0-59
Hour 0-23
Date 1-31
Month 1-12 (or names)
Day of Week 0-6 (or names) [ 0 is for Sunday ]
EXAMPLES
Example 1: Cleaning up core files
This example cleans up core files every weekday morning at
3:15 am:
Code:
15 3 * * 1-5 find $HOME -name core 2>/dev/null | xargs rm -f
Example 2: Mailing a birthday greeting
Code:
0 12 14 2 * mailx john%Happy Birthday!%Time for lunch.
Code:
0 12 14 2 * mailx john%Happy Birthday!%Time for lunch. > /dev/tty1
[ displays terminal 1 ]
Example 3: Specifying days of the month and week
This example
would run a command on the first and fifteenth of each
month, as well as on every Monday.
To specify days by only one field, the other field should be
set to *. For example:
would run a command only on Mondays.
crontab -e username Edit your crontab file, or create one if it doesn't already exist.
crontab -l username Display your crontab file.
crontab -r username Remove your crontab file.
CRONTAB Restrictions
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You can execute crontab if your name appears in the file /usr/lib/cron/cron.allow. If that file does not exist, you can use crontab if your name does not appear in the file /usr/lib/cron/cron.deny.
If only cron.deny exists and is empty, all users can use crontab. If neither file exists, ONLY the root user can use crontab. The allow/deny files consist of one user name per line