Difference between revisions of "Cron"
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| Line 22: | Line 22: | ||
* * means each tick is matched. | * * means each tick is matched. | ||
| + | * */5 means each 5th tick is matched | ||
* A range is defined by a dash. E.g. 2-5 in minute -> execute command on minute 2,3,4 and 5 | * A range is defined by a dash. E.g. 2-5 in minute -> execute command on minute 2,3,4 and 5 | ||
* A list is defined by comma's E.g. 2,4,6 in minute -> execute command on minute 2, 4 and 6 | * A list is defined by comma's E.g. 2,4,6 in minute -> execute command on minute 2, 4 and 6 | ||
Revision as of 21:12, 16 February 2021
Timed execution of commands. The cron daemon is checking the crontab every minute to see if anything needs to be done
- Format of crontab
| minute | hour | day-of-month | month | day-of-week | command |
|---|---|---|---|---|---|
| 1-59 | 1-23 | 1-31 | 1-12 | 0-7 | doit |
In scheduling fields (all except the command) following applies:
- * means each tick is matched.
- */5 means each 5th tick is matched
- A range is defined by a dash. E.g. 2-5 in minute -> execute command on minute 2,3,4 and 5
- A list is defined by comma's E.g. 2,4,6 in minute -> execute command on minute 2, 4 and 6
- For month and day-of-week also names can be used by giving the first 3 characters (case insensitive)
- For cron the week starts on Sunday so 0 is Sunday, 7 is Saturday
Example: Every Sunday at noon execute my script:
00 12 * * sun /usr/local/bin/myscript.sh
00 12 * * 0 /usr/local/bin/myscript2.sh
- crontab -l
- List the current crontab
- crontab <crontabfile>
- Load the file into the crontab, all existing content will be replaced. In the end a user crontab is stored in /var/spool/cron/crontabs/<username>. Don't edit it there, the cron daemon will only read it if told so by the crontab command.
- crontab -e
- Edit the current crontab directly in the default editor. Change the default editor by setting the EDITOR environment variable.