Crontab overview

2020-01-23 230 words 2 minutes

What is crontab

Crontab is a toll to schedule commands. You can run your terminal command on a specific schedule like run a command every day or every weekends.

Basic command

crontab [-u user] {-l | -e | -r}

command	utility
-l	list your cron job
-r	remove your cron job
-e	edit your cron job
-u	specific a user

How to schedule a command

Cron job looks like:

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# ┌───────────── minute (0 - 59)
# │ ┌───────────── hour (0 - 23)
# │ │ ┌───────────── day of month (1 - 31)
# │ │ │ ┌───────────── month (1 - 12)
# │ │ │ │ ┌───────────── day of week (0 - 6) (Sunday to Saturday;
# │ │ │ │ │                                       7 is also Sunday on some systems)
# │ │ │ │ │
# │ │ │ │ │
# * * * * *  command_to_execute

# export date into a file every minutes
* * * * * date >> ~/Desktop/test.txt

# Mon to Fri, 2:00, 2:30 , 4:00, 4:30
*/30 2,4 * * 1-5 echo "hello world"

symbol	meaning
*	any value
,	value list separator
-	range of value
/	step values

crontab.guru

crontab.guru which is a website to check whether your schedule is correct.

Reference

Thanks Corey Schafer’s video