Book Image

Linux Shell Scripting Cookbook, Second Edition - Second Edition

Book Image

Linux Shell Scripting Cookbook, Second Edition - Second Edition

Overview of this book

The shell remains one of the most powerful tools on a computer system — yet a large number of users are unaware of how much one can accomplish with it. Using a combination of simple commands, we will see how to solve complex problems in day to day computer usage.Linux Shell Scripting Cookbook, Second Edition will take you through useful real-world recipes designed to make your daily life easy when working with the shell. The book shows the reader how to effectively use the shell to accomplish complex tasks with ease.The book discusses basics of using the shell, general commands and proceeds to show the reader how to use them to perform complex tasks with ease.Starting with the basics of the shell, we will learn simple commands with their usages allowing us to perform operations on files of different kind. The book then proceeds to explain text processing, web interaction and concludes with backups, monitoring and other sysadmin tasks.Linux Shell Scripting Cookbook, Second Edition serves as an excellent guide to solving day to day problems using the shell and few powerful commands together to create solutions.
Table of Contents (16 chapters)
Linux Shell Scripting Cookbook
Credits
About the Authors
About the Reviewers
www.PacktPub.com
Preface
Index

Scheduling with cron


It is a common requirement to schedule execution of scripts at a given time or at given time intervals. The GNU/Linux system comes with different utilities for scheduling tasks. cron is such a utility that allows tasks to automatically run in the background of the system at regular intervals using the cron daemon. The cron utility makes use of a file called cron table that stores a list of schedules of scripts or commands to be executed and the time at which they are to be executed. A common example usage is that you can schedule downloads of files from the Internet during the free hours (certain ISPs provide free usage hours, usually, at night time). This way you won't be required to wake up in the night to start the download. In addition to writing a cron entry and schedule the download, you can also schedule to drop the Internet connection automatically and shutdown the system when the free usage hours end.

Getting ready

The cron scheduling utility comes with all the...