This directory of Linux commands is from Linux in a Nutshell, 5th Edition.
Click on any of the 687 commands below to get a description and list of available options. All links in the command summaries point to the online version of the book on Safari Bookshelf.
crontab [options] [file]
View, install, or uninstall your current crontab file. A privileged user can run crontab for another user by supplying -u user. 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:
Use a comma between multiple values, a hyphen to indicate a range, and an asterisk to indicate all possible values. For example, assuming these crontab entries:
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 1st and 15th of each month.
The superuser can always issue the crontab command. Other users must be listed in the file
The -e, -l, and -r options are not valid if any files are specified.