Book Image

Linux Shell Scripting Bootcamp

By : James K Lewis
Book Image

Linux Shell Scripting Bootcamp

By: James K Lewis

Overview of this book

Linux Shell Scripting Bootcamp is all about learning the essentials of script creation, validating parameters, and checking for the existence of files and other items needed by the script. We will use scripts to explore iterative operations using loops and learn different types of loop statements, with their differences. Along with this, we will also create a numbered backup script for backup files. Further, you will get well-versed with how variables work on a Linux system and how they relate to scripts. You’ll also learn how to create and call subroutines in a script and create interactive scripts. The most important archive commands, zip and tar, are also discussed for performing backups. Later, you will dive deeper by understanding the use of wget and curl scripts and the use of checksum and file encryption in further chapters. Finally, you will learn how to debug scripts and scripting best practices that will enable you to write a great code every time! By the end of the book, you will be able to write shell scripts that can dig data from the web and process it efficiently.
Table of Contents (19 chapters)
Linux Shell Scripting Bootcamp
About the Author
About the Reviewer
Customer Feedback

Using loops

One of the most important features of any programming language is the ability to perform a task, or tasks, a number of times and then stop when an ending condition is met. This is accomplished by using a loop.

The next section shows an example of a very simple while loop:

Chapter 3 - Script 1

# 5/2/2017
echo "script1 - Linux Scripting Book"
while [ $x -le 10 ]
 echo x: $x
 let x++

echo "End of script1"

exit 0

And here is the output:

We start by setting variable x to 1. The while statement checks to see if x is less than or equal to 10 and if so, runs the commands between the do and done statements. It will continue to do this until x equals 11, in which case the lines after the done statement are then run.

Run this on your system. It is very important to understand this script so that we can move on to more advanced loops.

Let's look at another script in the next section—see if you can determine what is wrong with it.

Chapter 3 - Script 2

# 5/2...