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Linux Desktop Hacks
book

Linux Desktop Hacks

by Nicholas Petreley, Jono Bacon
March 2005
Beginner to intermediate content levelBeginner to intermediate
342 pages
15h 55m
English
O'Reilly Media, Inc.
Content preview from Linux Desktop Hacks
Automate Your Life with cron #70
Chapter 9, Administration and Automation
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217
HACK
An important point to note is that cron does not actually perform these
activities itself. cron’s only function is to trigger a specific process or series of
commands at a certain time. When the specified time occurs, the com-
mands and tools that are needed to complete the activity are run. As such, to
automate a process on your computer, you need to determine how you can
complete your task with a series of command-line tools. This usually means
you need to create a script with the commands for cron to run at specified
intervals.
Create a Cronjob
The cron program reads in a special file called a crontab. This file specifies
jobs to be run and their times. You can access this file by running:
foo@bar:~$ crontab -e
This command uses the system’s default command-line editor so that you
can edit the crontab. If you want to set this editor to a different one (such as
jed), set the
$EDITOR environment variable prior to editing crontab:
foo@bar:~$ export EDITOR=jed
If this is your first use of cron, it is likely that your crontab is empty; unless
some special system cronjobs were added (these automatically added
crontabs are quite common in a number of Linux tools and utilities). Each
cronjob consists of a single line containing the time of the cronjob, as well
as the command to run.
A simple example of a crontab entry is:
30 ...
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Publisher Resources

ISBN: 0596009119Supplemental ContentCatalog PageErrata