Book Image

Learning Linux Shell Scripting - Second Edition

By : Ganesh Sanjiv Naik
Book Image

Learning Linux Shell Scripting - Second Edition

By: Ganesh Sanjiv Naik

Overview of this book

Linux is the most powerful and universally adopted OS. Shell is a program that gives the user direct interaction with the operating system. Scripts are collections of commands that are stored in a file. The shell reads this file and acts on commands as if they were typed on the keyboard. Learning Linux Shell Scripting covers Bash, GNU Bourne Again Shell, preparing you to work in the exciting world of Linux shell scripting. CentOS is a popular rpm-based stable and secured Linux distribution. Therefore, we have used CentOS distribution instead of Ubuntu distribution. Linux Shell Scripting is independent of Linux distributions, but we have covered both types of distros. We start with an introduction to the Shell environment and basic commands used. Next, we explore process management in Linux OS, real-world essentials such as debugging and perform Shell arithmetic fluently. You'll then take a step ahead and learn new and advanced topics in Shell scripting, such as decision making, starting up a system, and customizing a Linux environment. You will also learn about grep, stream editor, and AWK, which are very powerful text filters and editors. Finally, you'll get to grips with taking backup, using other language scripts in Shell Scripts as well as automating database administration tasks for MySQL and Oracle. By the end of this book, you will be able to confidently use your own shell scripts in the real world.
Table of Contents (17 chapters)

sed – non-interactive stream editor

The stream editor (sed) is a very popular non-interactive stream editor. Normally, whenever we edit files using the vi editor, we need to open the file using the vi command, then we interact with the file to see the content of the file on screen, then edit it, and then save the file. Using sed, we can type commands on the command line and sed will make the changes to the text file. sed is a non-destructive editor. sed makes the changes to the file and displays the content on screen. If we want to save the changed file, then we need to redirect the output of sed to the file.

The procedure to install sed is shown here.

For Ubuntu or any Debian-based distributions, enter the following command:

    $ apt-get install sed
  

For Red Hat or any rpm-based distribution enter the following command:

    $ yum install sed
  

To check the version...