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

Understanding functions


We, human beings, in our day-to day lives, take help from people, who are specialized in certain knowledge or skills, such as doctors, lawyers, and barbers. This helps our lives to be more organized and comfortable so that we need not learn every skill in this world. We take advantage of skills that have already been acquired by other people. The same thing applies to software development as well. If we use whatever code or scripts that have already been developed, then this will save our time and energy.

In real-world scripts, we break down big tasks or scripts into smaller logical tasks. This modularization of scripts helps in the better development and understanding of code. The smaller logical blocks of script are be called functions.

The advantages of functions are as follows:

  • If the script is very big, then understanding it becomes very difficult. Using functions, we can easily understand complex script through logical blocks or functions.

  • When a big and complex...