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Cron Tutorial - Advanced Usage

The below cron usage information is optional and is intended for more advanced users.

1. Crontab Editing

Usually, a user would edit a file containing crontab entries and load the file after making changes.

machine:~$ crontab myfile

It is also possible to directly edit the actual crontab file used by the cron daemon.

machine:~$ crontab -e

Specifying the -e option will launch the default editor (usally vi) to modify the actual crontab file. After the user exists the editor, the crontab file is updated.

2. Advanced Formatting

The first part of this cron tutorial deals with the basic crontab format. Slightly more advanced options exist.

59 17 1,10,20,30 * * /home/username/backupsite

This would execute the ask on the 1st, the 10th, the 20th and on the 30th of each month, at 17:59PM.

59 17 * * 1-5 /home/username/backupsite

This would execute the cron job on weekdays only.

59 */6 * * * /home/username/backupsite

Here, the tasks is executed every 4 hours (24/6 =4).

These techniques can be used on all the crontab fields.

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