Mac OS X in a Nutshell

Name

crontab

Synopsis

crontab [file]
crontab options [user]

Runs crontab on your current crontab file, or specifies a crontab file to add to the crontab directory. A privileged user can run crontab for another user by supplying a user after any of the options.

A crontab file is a list of commands, one per line, that will execute automatically at a given time. Numbers are supplied before each command to specify the execution time. The numbers appear in five fields, as follows:

Minute        0-59
Hour          0-23
Day of month  1-31
Month         1-12
Day of week   0-6, with 0 = Sunday

Use a comma between multiple values, a hyphen to indicate a range, and an asterisk to indicate all possible values. For example, assuming the crontab entries below:

59 3 * * 5        find / -print | backup_program
0 0 1,15 * *      echo "Timesheets due" | mail user

The first command backs up the system files every Friday at 3:59 a.m., and the second command mails a reminder on the 1^st and 15^th of each month.

Options

-e

Edit the user’s current crontab file (or create one).

-l

List the user’s file in the crontab directory.

-r

Delete the user’s file in the crontab directory.