CronCron is a task-scheduler, which can execute a pre-set command at a specific date and time. It can be used to re-boot your system, to run an e-mail program at a certain time of day, to download newsgroup articles, or to remember important dates and times.
Cron is a time-saving device named, appropriately enough, after Chronus, the Greek god of time. Using one feature, Crontab, you can manage your time on the computer more effectively by scheduling routine tasks for "off hours", while you're away or during low server load. Crontab uses a text file to store time and program references. To create or edit a Crontab file, you would type:
crontab -e
A typical Crontab entry would look something like this:
* 4 * * * /usr/u/m/mcintyre/.dilbert_get
The first five fields deal with minute, hour, day of month, month, and day of the week, respectively. The asterisk is used both as a place holder and to instruct Crontab not to consider the specific time unit in the scheduling of the program. In the above example, the entry would execute the specified task at 4 AM every day.