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Crontab format |
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Subject: Crontab format
Author: Linux
In response to: crontab -- schedule tasks on Linux
Posted on: 09/03/2012 05:27:01 PM
Cronjobs are expressed in two formats: in number or in keyword.
Numberical format
* * * * * /bin/execute/this_script.sh
As you can see there are 5 stars. The stars represent different date parts in the following order: 1st * -- minute (from 0 to 59)
2nd * -- hour (from 0 to 23)
3rd * -- day of month (from 1 to 31)
4th * -- month (from 1 to 12)
5th * -- day of week (from 0 to 6) (0=Sunday)
Note: If you leave the star, or asterisk, it means every. By default, ***** means that the task is being executed every minute.
Keyword format
@<keyword> /bin/execute/this_script.sh
Here are some useful keywords instead of a number:
@reboot Run once, at startup
@yearly Run once a year "0 0 1 1 *"
@annually (same as @yearly)
@monthly Run once a month "0 0 1 * *"
@weekly Run once a week "0 0 * * 0"
@daily Run once a day "0 0 * * *"
@midnight (same as @daily)
@hourly Run once an hour "0 * * * *
>
> On 09/03/2012 05:10:11 PM Linux wrote:
If you want some maintenance tasks (creating backups, synchronizing caches, and scheduling update on statistics) to be automatically run in the background at regular intervals, you can achieve it on Linux by crontab.
The crontab (cron derives from chronos, Greek for time; tab stands for table) command, found in Unix and Unix-like operating systems, is used to schedule commands to be executed periodically. To see what crontabs are currently running on your system, you can open a terminal and run:
To edit the list of cronjobs you can run:
References:
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