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 variables in scripts

A variable is simply a placeholder for some value. The value can change; however, the variable name will always be the same. Here is a simple example:


This assigns the value 1 to variable a. Here's another one:


To display what a variable contains use the echo statement:

   echo Variable a is: $a


Notice the $ preceding the variable name. This is required in order to show the contents of the variable.

If at anytime, you aren't seeing the results you expect first check for the $.

Here's an example using the command line:

$ a=1
$ echo a
$ echo $a
$ b="Jim"
$ echo b
$ echo $b

All variables in a Bash script are considered to be strings. This is different than in a programming language such as C, where everything is strongly typed. In the preceding example, a and b are strings even though they appear to be integers.

Here's a short script to get us started:

Chapter 2 - Script 1

# 6/13/2017
echo "script1"

# Variables