An entry in a crontab file looks like this:
m h dom mon dow command
where m = minutes, h = hours, dom = day of month, mon = month, and dow = day of week. cron will automatically run the specified command whenever the time matches the specified time. To indicate "any", use an asterisk (*). So to get something to run at 5pm every day, you would add the following line to your crontab file:
00 17 * * *
Make sure to use crontab -e to edit your crontab file. The actual files are stored in /var/spool/cron/crontabs/, but you shouldn't edit those files directly.
Pasted from wikipedia:
# .---------------- minute (0 - 59) # | .------------- hour (0 - 23) # | | .---------- day of month (1 - 31) # | | | .------- month (1 - 12) OR jan,feb,mar,apr ... # | | | | .---- day of week (0 - 6) (Sunday=0 or 7) OR sun,mon,tue,wed,thu,fri,sat # | | | | | * * * * * command to be executed
Update 2012-08-13: still can't get cron working (Lucid)
This page provided some hints: http://aplawrence.com/Unixart/crontab_not_running.html
/var/log/syslog did not show the cron jobs running
chkconfig --list | grep cron indicated that cron was off:
cron 0:off 1:off 2:off 3:off 4:off 5:off 6:off
