The Cron Job/Crontab
To have your task run at this frequency, use the following cron:
40 */4 * * *
This cron command translates to the following (in Human-Readable format):
“Every 4 hours at 40 minutes past the hour.”
What is a Cron Job & Crontab?
A cron job is a Linux utility used for scheduling the execution of commands or scripts at a specified time and date. Cron is typically used for system maintenance or administration, such as running backups or log rotation.
Crontab files are typically stored in the /etc/crontab file, but they can also be stored in individual user’s home directories. To edit your own crontab file, you can use the command “crontab -e”. This will open up the file in your default text editor.
Every cron job uses five fields. Here is an explanation of what each field does in this cron, which runs “every 4 hours at 40 minutes past the hour“:
FUN FACT: Cron jobs are named after the Greek god of time, Chronos – so now you know where the name comes from!.
You might want to set up a crontab or cron job to run every 4 hours at 40 minutes past the hour for several reasons, including:
- Run a script to update software every 4 hours
- Run a script to backup data every 4 hours
- Run a script to send out an email report every 4 hours
- Run a script to check for new users every 4 hours
Similar Cron Jobs
You might also want to run a crontab:
- every 5 hours
- every 12 hours
- every 9 hours
- every 8 hours
- every 11 hours at 50 minutes past the hour
- every hour between 1:00 pm and 6:00 pm
FUN FACT: If you need to temporarily disable a cron job, you can simply comment out the line in the crontab file that corresponds to that particular task..
In this article, you learned how to set up a cron job that runs every 4 hours at 40 minutes past the hour. 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.