The Cron Job/Crontab
To have your task run at this frequency, use the following cron:
0 21 */3 * *
This cron command translates to the following (in Human-Readable format):
“Every 3 days at 9:00 pm.”
What is a Cron Job & Crontab?
A cron job is a task that is scheduled to run at a specific time or interval. Cron jobs are typically used for maintenance tasks, such as backing up data or updating software.
A crontab is a text file containing a list of commands that are executed at specified times. The commands in the crontab are executed by the cron daemon, which runs in the background and checks for new entries every minute.
Every cron job uses five fields. Here is an explanation of what each field does in this cron, which runs “every 3 days at 9:00 pm“:
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 days at 9:00 pm for several reasons, including:
- Automatically update software
- Automatically back up files
- Perform system maintenance tasks
Similar Cron Jobs
You might also want to run a crontab:
- every 2 days
- every 1 day
- every 7 days
- every 8 days
- every 8 days at 7:30 am
- every 4 days at 9:30 am
- every 6 days at 3:30 am
FUN FACT: The most common way to edit cron jobs is using the crontab command – this stands for “cron table,” and it contains all the information about when your tasks should be executed..
In this article, you learned how to set up a cron job that runs every 3 days at 9:00 pm. 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.