Cron

Cron syntax is used to schedule when jobs should run.

You may need to use a cron syntax string to create a pipeline schedule, or to prevent unintentional releases by setting a deploy freeze.

Cron syntax

Cron scheduling uses a series of five numbers, separated by spaces: 

# ┌───────────── minute (0 - 59)
# │ ┌───────────── hour (0 - 23)
# │ │ ┌───────────── day of the month (1 - 31)
# │ │ │ ┌───────────── month (1 - 12)
# │ │ │ │ ┌───────────── day of the week (0 - 6) (Sunday to Saturday)
# │ │ │ │ │
# │ │ │ │ │
# │ │ │ │ │
# * * * * * <command to execute>

(Source: Wikipedia)

In cron syntax, the asterisk (*) means ‘every,’ so the following cron strings are valid:

  • Run once an hour at the beginning of the hour: 0 * * * *
  • Run once a day at midnight: 0 0 * * *
  • Run once a week at midnight on Sunday morning: 0 0 * * 0
  • Run once a month at midnight of the first day of the month: 0 0 1 * *
  • Run once a month on the 22nd: 0 0 22 * *
  • Run once a month on the 2nd Monday: 0 0 * * 1#2
  • Run once a year at midnight of 1 January: 0 0 1 1 *
  • Run every other Sunday at 0900 hours: 0 9 * * sun%2
  • Run twice a month at 3 AM, on the 1st and 15th of the month: 0 3 1,15 * *

For complete cron documentation, refer to the crontab(5) — Linux manual page. This documentation is accessible offline by entering man 5 crontab in a Linux or MacOS terminal.

Cron examples 

# Run at 7:00pm every day:
0 19 * * *

# Run every minute on the 3rd of June:
* * 3 6 *

# Run at 06:30 every Friday:
30 6 * * 5

More examples of how to write a cron schedule can be found at crontab.guru.

How GitLab parses cron syntax strings

GitLab uses fugit to parse cron syntax strings on the server and cron-validator to validate cron syntax in the browser. GitLab uses cRonstrue to convert cron to human-readable strings in the browser.