Crontab is a utility on the CentOS operating system that allows you to schedule recurring tasks at a predetermined time. Here are instructions for using crontab on CentOS:
Step 1: Open crontab for the current user
To open crontab for the current user, run the following command:
Step 2: Understand the crontab syntax
Each line in the crontab represents a specific scheduled task.
The crontab syntax is as follows:
* * * * * command_to_be_executed - - - - - | | | | | | | | | ----- Day of the week (0 - 7) (Sunday is 0 and 7) | | | ------- Month (1 - 12) | | --------- Day of the month (1 - 31) | ----------- Hour (0 - 23) ------------- Minute (0 - 59)
The asterisk (*) means all possible values for that field.
Step 3: Define tasks in the crontab
For example, to run a script named "myscript.sh" at 1 AM every day, add the following line to the crontab:
0 1 * * * /path/to/myscript.sh
Step 4: Save and exit
After adding tasks to the crontab, save and exit by pressing
Ctrl + X, then type
Y and press
Step 5: View crontab
To view the list of tasks in the crontab, run the following command:
Step 6: Remove a task from the crontab
o remove a task from the crontab, run the following command:
Note: Be careful when using crontab, ensure the syntax and scheduling time are correct to avoid system malfunction or overload.