Cron

cron is basically a job scheduler that can help automate many conventional but repeatedly used functionality.

Cron works using the crontab file.

It is a file that lists all the scheduled jobs and when to perform them.

On a standard Linux machine, there are different crontab files based on user privileges. We’ll mostly base our examples on the default users’ crontab.

crontab is the command that allows us to modify crontab files and cron executes them.

The jobs inside the crontab file are known as cron jobs, and consist of standard Linux commands. They also contain the time-period when cron needs to execute them.

 ┌───────────── minute (0 - 59)
 │ ┌───────────── hour (0 - 23)
 │ │ ┌───────────── day of the month (1 - 31)
 │ │ │ ┌───────────── month (1 - 12)
 │ │ │ │ ┌───────────── day of the week (0 - 6) (Sunday to Saturday;
 │ │ │ │ │                                   7 is also Sunday on some systems)
 │ │ │ │ │
 │ │ │ │ │
 * * * * * <command to execute>