Contents

Overview

Cron is the time-based job scheduler in Unix-like computer operating systems.
Cron enables users to schedule jobs (commands or shell scripts) to run periodically at certain times or dates.
It is commonly used to automate system maintenance or administration, though its general-purpose nature means that it can be used for other purposes.

General Information

To edit the Cron Table use:
crontab -e

To view the Cron Table use:
crontab -l

The crontab file

Minute	Hour	Day of Month	Month	Day of Week	Command
(0-59)	(0-23)	(1-31)	(1-12 or Jan-Dec)	(0-6 or Sun-Sat)

Using Cron Examples

Run ‘check.sh’ script every 3 Minutes :
*/3 * * * * /scripts/check.sh

Run ‘check.sh’ script every Day at 07:00 :
0 7 * * * /scripts/check.sh

Run ‘check.sh’ script every 24th of the Month at 13:10 :
10 13 24 * * /scripts/check.sh

Run ‘check.sh’ script every Sunday at 21:53 :
53 21 * * 0 /scripts/check.sh

Additional Info

Adding Environment Variables :
Cron doesn’t export any of the profile files,
so if you need a path variable you can set it in crontab (using crontab -e) :
PATH=$PATH:/sbin:/bin/usr/local/bin:/usr/local/sbin:/scripts 0 * * * * root /scripts/check.sh