Crontab Schedule

Crontab Schedule
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Go into your crontab file

sudo crontab -l
sudo crontab -e

Scheduling format

* * * * * /bin/execute/this/script.sh

The * meaning in different position

Position (From left to right) Description Range
1 Minute 0-59
2 Hour 0-23
3 nth day of the month 1-31
4 nth month of the year 1-12
5 day of the week 0-6, 0: Sunday

The * means it will match in every time when run the crontab command

Special Character

@reboot     Run 1 time when reboot
@yearly     Run 1 time every year     "0 0 1 1 *"
@annually   (Same as @yearly)
@monthly    Run 1 time every month    "0 0 1 * *"
@weekly     Run 1 time every week     "0 0 * * 0"
@daily      Run 1 time every day      "0 0 * * *"
@midnight   (Same as @daily)
@hourly     Run 1 time every hour     "0 * * * *"

Output your command result to garbage collection and show nothing

*/10 * * * * /bin/execute/this/script.sh > /dev/null 2>&1

Test crontab

You can run the crontab command directly to make sure that every setting in the crontab file is correct.

crontab path/to/crontab/file

If there is some setting wrong in the crontab file, then it will show the error message.

"/etc/crontab":165: bad day-of-month
errors in crontab file, can\'t install.

Reference