Name
crontab
Synopsis
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:
Minute 0-59 Hour 0-23 Day of month 1-31 Month 1-12 Jan, Feb, Mar, ... Day of week 0-6, with 0 = Sunday Sun, Mon, Tue, ...
Use a comma between multiple values, a hyphen to indicate a range, an asterisk to indicate all possible values, and a slash (/) to indicate a repeating range. For example, assuming these crontab entries:
59 3 * * 5 find / -print |backup_program
0 0 1,15 * * echo "Timesheets due" | mailuser
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 /etc/cron.allow if it exists; otherwise, they must not be listed in /etc/cron.deny. If neither file exists, only the superuser can issue the command.
Options
The -e, -l, and -r options are not valid if any files are specified.
- -e
Edit the user’s current crontab file (or create one).
- -l
Display the user’s crontab file on standard output.
- -r
Delete the user’s crontab file.
- -u user
Indicate which user’s crontab file will be acted upon.
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