Cron

Timed execution of commands. The cron daemon is checking the crontab every minute to see if anything needs to be done

Format of crontab

minute	hour	day-of-month	month	day-of-week	command
1-59	1-23	1-31	1-12	0-7	doit

In scheduling fields (all except the command) following applies:

• * means each tick is matched.
• A range is defined by a dash. E.g. 2-5 in minute -> execute command on minute 2,3,4 and 5
• A list is defined by comma's E.g. 2,4,6 in minute -> execute command on minute 2, 4 and 6
• For month and day-of-week also names can be used by giving the first 3 characters (case insensitive)

Example: Every Sunday at noon execute my script:
00 12 * * sun /usr/local/bin/myscript.sh

crontab -l

List the current crontab