December 2008
Intermediate to advanced
320 pages
6h 45m
English
The system scheduler on UNIX and Linux systems is called cron. Its purpose is to run commands, series of commands, or scripts on a predetermined schedule. Normally these tasks are performed on systems that run 24 hours a day, 7 days a week. Writing cron scripts to perform system maintenance, backups, monitors, or any other job that you would want to run on a schedule is a very common task. There are a few subtleties with cron however, that many users and administrators may be unaware of.
On a UNIX or Linux system, the cron daemon process runs all the time. A daemon is generally a program that runs as a background task and provides some type of service, in this case a scheduler. A run control (rc) script starts ...