Cron Examples

Cron is kinda like the 'at' command only a hell of a lot better, but essentially it is used to running commands/scripts in the background at regular intervals. 

To create or edit a crontab file add the following command into your shell:

crontab -e

This will bring up a screen much like the following:

Your commands will go at the bottom of this page.

Crontab is a simple text file with a list of commands meant to be run at a certain time. The commands are controlled by Cron which executes them in the background. If you want to set a script to run on you system at regular intervals something like the below command should be added to the crontab file shown above:

30 15 16 2 1 /scripts/test/

This doesn't seem to make much sense at first glance but let me try and explain. The first five numbers indicate at what intervals you wish to run your command/script, this is the breakdown:

1 Minute 0-59
2 Hour 0-23 (0 = midnight)
3 Day 1-31
4 Month 1-12
5 Weekday 0-6 (0 = Sunday)
* = all
So we can see that I am asking Cron to run my script at 15:30 on the 16th February, Monday, plus every Monday in February. You could have it run everyday at 15:30 no matter what the date is:

30 15 * * * /scripts/test/

Make sure you give each a new line after each cron job, otherwise the job will not be executed...god knows why.. To save a cron-job press 'ctrl-K-X'.
One of the jewels of Linux in my opinion.  

more information can be found with 'man crontab' from your console.


  1. Like! Sometimes linux commands are not explained for the average human being! This is good thanks!

  2. No problem Dan, Thanks for making the first comment!