2020-10-24 23:57:45 +05:30
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# Cron
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Cron syntax is used to schedule when jobs should run.
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You may need to use a cron syntax string to
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[trigger nightly pipelines](../../ci/triggers/README.md#using-cron-to-trigger-nightly-pipelines),
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create a [pipeline schedule](../../api/pipeline_schedules.md#create-a-new-pipeline-schedule),
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or to prevent unintentional releases by setting a
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[deploy freeze](../../user/project/releases/index.md#prevent-unintentional-releases-by-setting-a-deploy-freeze).
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## Cron syntax
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Cron scheduling uses a series of five numbers, separated by spaces:
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```plaintext
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# ┌───────────── minute (0 - 59)
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# │ ┌───────────── hour (0 - 23)
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# │ │ ┌───────────── day of the month (1 - 31)
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# │ │ │ ┌───────────── month (1 - 12)
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# │ │ │ │ ┌───────────── day of the week (0 - 6) (Sunday to Saturday)
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# │ │ │ │ │
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# │ │ │ │ │
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# │ │ │ │ │
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# * * * * * <command to execute>
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```
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2021-01-03 14:25:43 +05:30
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(Source: [Wikipedia](https://en.wikipedia.org/wiki/Cron))
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2020-10-24 23:57:45 +05:30
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In cron syntax, the asterisk (`*`) means 'every,' so the following cron strings
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are valid:
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- Run once an hour at the beginning of the hour: `0 * * * *`
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- Run once a day at midnight: `0 0 * * *`
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- Run once a week at midnight on Sunday morning: `0 0 * * 0`
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- Run once a month at midnight of the first day of the month: `0 0 1 * *`
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- Run once a year at midnight of 1 January: `0 0 1 1 *`
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For complete cron documentation, refer to the
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[crontab(5) — Linux manual page](https://man7.org/linux/man-pages/man5/crontab.5.html).
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This documentation is accessible offline by entering `man 5 crontab` in a Linux or MacOS
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terminal.
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## Cron examples
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```plaintext
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# Run at 7:00pm every day:
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0 19 * * *
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# Run every minute on the 10th of June:
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* * 3 6 *
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# Run at 06:30 every Friday:
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30 6 * * 5
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```
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More examples of how to write a cron schedule can be found at
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[crontab.guru](https://crontab.guru/examples.html).
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## How GitLab parses cron syntax strings
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GitLab uses [fugit](https://github.com/floraison/fugit) to parse cron syntax
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strings on the server and [cron-validate](https://github.com/Airfooox/cron-validate)
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to validate cron syntax in the browser.
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