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

Exiting from the current loop iteration with the continue command


With the help of the continue command, it is possible to exit from the current iteration of the loop and to resume the next iteration of the loop. We use the for, while, or until commands for loop iterations.

The following is the for_09.sh script for the loop with the continue command to skip a certain part of the loop commands:

#!/bin/bash
for x in 1 2 3
do
    echo before $x
    continue 1
    echo after $x
done
exit 0

Let's test the program:

$ chmod +x for_09.sh
$ ./for_09.sh

The following will be the output after executing the preceding commands:

before 1
before 2
before 3

The following is the for_10.sh script, in which we will check all files and directories. If the file is found, we will print the name. If the directory is found, we will skip further processing with the continue command. Take care that any of your useful files with the name sample* are not in the testing directory before testing this script:

#!/bin/bash...