Crontab

edits a user's cron table -- hence the name -- by running an editor. The actual tables for each user are kept in /etc/cron/tabs but are not meant to be edited directly.

The tables are in this format:

#min hour dayofmonth  monthofyear  dayofweek  command
0    12      14         2           *        fsck -y

Time values can be set to * (for all) or * divided -- e.g., */5 in the first field means "every five minutes"

Common flags

-u username edit username table
-e edit table (or create empty one if none exists)
-r remove table
-l list the current table