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

Working with arrays


An array is a list of variables. For example, we can create an array FRUIT, which will contain many fruit names. The array does not have a limit on how many variables it may contain. It can contain any type of data. The first element in an array will have the index value as 0:

student@ubuntu:~$ FRUITS=(Mango Banana Apple)
student@ubuntu:~$ echo ${FRUITS[*]}
Mango Banana Apple
student@ubuntu:~$ echo $FRUITS[*]
Mango[*]
student@ubuntu:~$ echo ${FRUITS[2]}
Apple
student@ubuntu:~$ FRUITS[3]=Orange
student@ubuntu:~$ echo ${FRUITS[*]}
Mango Banana Apple Orange

Creating an array and initializing it

You will learn about creating an array in the Bash shell.

If the array name is FRUIT, then we can create an array as follows:

FRUIT[index]=value

Index is the integer value. It should be 0 or any positive integer value.

We can also create an array as follows:

$ declare -a array_name
$ declare -a arrayname=(value1 value2 value3)

Example:

$ declare -a fruit=('Mango' 'Banana' 'Apple' 'Orange...