The Cron Job/Crontab
To have your task run at this frequency, use the following cron:
*/21 * * * *
This cron command translates to the following (in Human-Readable format):
“Every 21 minutes.”
What is a Cron Job & Crontab?
A cron job is a time-based task that is set to run at specific intervals. This can be anything from running a script every hour to backing up a database every day. Cron jobs are typically used for maintenance tasks or tasks that need to be performed regularly, such as checking for updates or sending out reports.
A crontab is a file containing commands and instructions for the cron daemon to execute. The crontab is used to schedule jobs (commands or shell scripts) to run periodically at certain times or dates.
Every cron job uses five fields. Here is an explanation of what each field does in this cron, which runs “every 21 minutes“:
FUN FACT: A common use for cron jobs is to generate periodic reports – for example, you could set up a cron job to automatically generate and send out a report on website traffic statistics every week..
You might want to set up a crontab or cron job to run every 21 minutes for several reasons, including:
- To run a script which updates some data every 21 minutes
- To send an email to a user every 21 minutes
- To check if a website is up every 21 minutes
Similar Cron Jobs
You might also want to run a crontab:
- every 18 minutes
- every 29 minutes
- every 28 minutes
- every 23 minutes
- every minute between 3:00 am and 7:00 pm
- every minute between 2:00 am and 3:00 am
FUN FACT: Cron jobs are named after the Greek god of time, Chronos – so now you know where the name comes from!.
In this article, you learned how to set up a cron job that runs every 21 minutes. Please share this page with friends and colleagues if you find it useful.
If you have any questions, please don’t hesitate to comment below.
If you are looking for cron jobs that run at certain minutes, hours, days, weekdays, or months, or if you are looking for miscellaneous cron jobs, then check out our relevant sections, or visit our cron job cheat sheet for a list of hundreds of popular cron jobs.