Book Image

Learning Linux Shell Scripting

By : Ganesh Sanjiv Naik
Book Image

Learning Linux Shell Scripting

By: Ganesh Sanjiv Naik

Overview of this book

Linux is the one of the most powerful and universally adopted OSes. 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 can read this file and act on the commands as if they were typed on the keyboard. Shell scripting is used to automate day-to-day administration, and for testing or product development tasks. This book covers Bash, GNU Bourne Again SHell, preparing you to work in the exciting world of Linux shell scripting. We start with an introduction to the Shell environment and explain basic commands used in Shell. Next we move on to check, kill, and control the execution of processes in Linux OS. Further, we teach you about the filter tools available in Linux and explain standard output and standard errors devices. Then we will ensure you understand Shell’s interpretation of commands and get a firmer grasp so you use them in practice. Next, you’ll experience some real-world essentials such as debugging and perform Shell arithmetic fluently. Then you’ll take a step ahead and learn new and advanced topics in Shell scripting, such as starting up a system and customizing a Linux system. Finally, you’ll get to understand the capabilities of scripting and learn about Grep, Stream Editor, and Awk.
Table of Contents (20 chapters)
Learning Linux Shell Scripting
Credits
About the Author
Acknowledgments
About the Reviewers
www.PacktPub.com
Preface
Index

sed – noninteractive stream editor


The stream editor (sed) is a very popular noninteractive 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, such as to see the content of the file on screen, then, edit it, and save the file. Using sed, we can type commands on the command line and sed will make the changes to the text file. The sed is a nondestructive editor. The 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 the 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 of sed, enter the following command:

$ sed –V

Otherwise, enter this command:

$ sed --version
GNU sed version 3.0
2

Understanding...