Programming Tutorials

crontab in Mac OS X

By: Strauss K in macos Tutorials on 2011-02-03  

crontab is a command-line utility in Mac OS X and other Unix-based operating systems that allows you to create, edit, and manage cron jobs.

A cron job is a scheduled task or command that runs automatically at specific times or intervals. To create a cron job using crontab, you need to add an entry to the crontab file, which is a configuration file that stores the list of jobs to be executed by cron.

Here are some basic commands for using crontab in Mac OS X:

To view the current crontab file, enter the following command in the Terminal:

crontab -l

This will display the list of cron jobs currently scheduled on your system.

To create a new cron job or edit an existing one, enter the following command in the Terminal:

crontab -e

This will open the crontab file in the default text editor for your Mac, allowing you to add or edit entries.

To remove all cron jobs, enter the following command in the Terminal:

crontab -r

This will delete the current crontab file and all its contents.

To create a new crontab file from a text file, enter the following command in the Terminal:

crontab file.txt

This will read the contents of file.txt and create a new crontab file based on its contents.

When creating a cron job using crontab, you need to specify the schedule for the job, along with the command or script to be executed. The syntax for a cron job entry is as follows:

* * * * * command

Here, the five asterisks represent the schedule for the job, in the following order:

Minute (0-59)
Hour (0-23)
Day of the month (1-31)
Month (1-12)
Day of the week (0-6, where Sunday is 0)

For example, to schedule a job to run every day at 2:30 PM, you could use the following crontab entry:

30 14 * * * command

This will run the command at 2:30 PM every day.

For more information on how to use crontab and create cron jobs in Mac OS X, you can refer to the manual page by running the following command in the Terminal:

man crontab