Two utilities are available to manage job scheduling. Which utility the user chooses should depend on what he is trying to accomplish. The first utility is cron. The cron utility is used to schedule events that will occur repeatedly at a fixed time. The second utility is at. The at utility is used to schedule events that will occur only once. I explain each of these utilities in the next sections.
Commands, including scripts, can be set to run on a schedule. This schedule allows fine-tuning for any combination of minutes, hours, day of the month, month of the year, day of the week. The cron file contains crontab entries. A crontab entry is one scheduled event. The following is the syntax of a crontab entry for a Linux system: ...