Revisione di Manage scheduled commands using crontab del Mer, 05/28/2025 - 14:56
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==Introduction==
This is a documentation about managing scheduled commands with '''crontab'''. With crontab, you can install, deinstall or list the tables used to drive the '''cron daemon'''. Each user can have their own crontab.
==Edit crontabs==
To start editing crontabs for the current user, run:
$ crontab -e
To manage crontabs as root, run:
$ sudo crontab -e
To edit crontabs as another specific user, run the following command. (Make sure you have the privileges for this user):
$ crontab -u USER -e
This will open the current crontab using an editor. If no VISUAL or EDITOR environment variables is set, you can choose one at start. To do this press a number on your keyboard and hit ENTER.
A configuration file will be shown. After you exit from your editor, the modified crontab will be installed automatically.
A line starting with '''#''' is a comment and will not be executed. By default, a description and an example will be shown. To add a cronjob, begin a new line, or edit one.
The format of each job follows this format:
MINUTE HOUR DAY-OF-MONTH MONTH DAY-OF-WEEK COMMAND-THAT-WILL-BE-EXECUTED
For each part of the table, you must either define a concrete value, or else type '''*''' (for "any"), or '''*/N''' (see example below). Use spaces to separate the parts or values from each other.
==Examples for crontabs==
To run a backup of all your user accounts at 5 a.m. every week, use:
0 5 * * 1 tar -zcf /var/backups/home.tgz /home/
To run a shell script every 2 hours (in this example, cron will execute the script ''myscript.sh'' in the ''home directory''), use:
* */2 * * * ~/myscript.sh
==List crontabs==
To list the crontabs for the current user, run:
$ crontab -l
