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
About the Authors
About the Reviewers

Text slicing and parameter operations

This recipe walks through some of the simple text-replacement techniques and parameter-expansion shorthands available in Bash. A few simple techniques can often help us avoid having to write multiple lines of code.

How to do it...

Let's get into the tasks.

Replacing some text from a variable can be done as follows:

$ var="This is a line of text"
$ echo ${var/line/REPLACED}
This is a REPLACED of text"

line is replaced with REPLACED.

We can produce a substring by specifying the start position and string length, by using the following syntax:


To print from the fifth character onwards, use the following command:

$ string=abcdefghijklmnopqrstuvwxyz
$ echo ${string:4}

To print eight characters starting from the fifth character, use the following command:

$ echo ${string:4:8}

The index is specified by counting the start letter as 0. We can also specify counting from the last letter as -1. It...