The Cron Job/Crontab
To have your task run at this frequency, use the following cron:
0 0 21 */3 *
This cron command translates to the following (in Human-Readable format):
“Every 3 months on day 21 of the month.”
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 backup script every night to sending out an email notification once a week. Cron jobs are typically used for maintenance or repetitive tasks.
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 3 months on day 21 of the month“:
FUN FACT: Cron jobs are named after the Greek god Chronos, who represents time itself..
You might want to set up a crontab or cron job to run every 3 months on day 21 of the month for several reasons, including:
- Checking for updates to a software package
- Generating reports
- Rotating log files
Similar Cron Jobs
You might also want to run a crontab:
- every 4 months
- every 6 months
- every 3 months
- every 2 months
- every 4 months on day 30 of the month
- every 4 months on day 22 of the month
- every 5 months on day 24 of the month
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 3 months on day 21 of the month. 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 crontab cheat sheet for a list of hundreds of popular cron jobs.