The Cron Job/Crontab
To have your task run at this frequency, use the following cron:
30 21 */4 * *
This cron command translates to the following (in Human-Readable format):
“Every 4 days at 9:30 pm.”
What is a Cron Job & Crontab?
In computing, a cron job is a time-based task that is set to run at certain predetermined times or intervals. A cron job can be used to schedule anything from basic tasks like running backups to more complex tasks like sending out email alerts or syncing files between servers. Cron jobs are typically used for maintenance or administrative tasks that need to be performed on a regular basis.
Crontab is a file that contains instructions for the cron daemon, which is a program that executes commands at specified intervals. Crontab files are typically edited with the crontab command, which allows users to create, edit, and delete their own crontab files.
Every cron job uses five fields. Here is an explanation of what each field does in this cron, which runs “every 4 days at 9:30 pm“:
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 4 days at 9:30 pm for several reasons, including:
- Sending out a reminder email for an event that happens every 4 days
- Backup data to disk every 4 days
- Generate a report on system usage every 4 days
Similar Cron Jobs
You might also want to run a crontab:
- every 8 days
- every 10 days
- every 3 days
- every 7 days
- every 1 day
- every 8 days at 4:00 pm
- every 7 days at 5:30 pm
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 4 days at 9:30 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.