Here in this post, we will be checking is What is crontab in Linux, Crontab syntax, crontab schedule, and how to edit the crontab, how to list the crontab content
What are Cron and Crontab
- Cron is a utility in which we can schedule jobs on a Unix system.
- Cron is driven by a crontab file, a configuration file that specifies shell commands to run periodically on a given schedule.
- Every user can have their own crontab file.
- Crontab file contains the cron strings and executable file
- cron strings is a set of five or six fields separated by white space that represents a set of times
- We can use crontab as an alternative for scheduling concurrent programs at application level.
Syntax of Crontab
Example of Crontab
00,15,30,45 * * * 1-6 /u01/app/check_load.sh 15,35,55 08-22 * * 1-6 /home/applmgr/scripts/check_forms_sessions.sh
Expression in Cron
How to edit the Crontab
crontab -e If you are doing with root user and want to edit for particuler user crontab -e <username>
How to list the crontab
crontab -l If you are doing with root user and want to edit for particuler user crontab -l <username>
How to remove the crontab file
crontab -r
If you are doing with root user and want to edit for a particular user
crontab -r <username>
Cron deamon
There runs a background process called cron daemon which runs the scripts in the crontab file as per the schedule. You can check that as
ps -ef|grep cron
I hope all this information on What is crontab in Linux, Crontab syntax, crontab schedule, and how to edit the crontab,how to list the crontab content help you in daily activities
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