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Learning Linux Shell Scripting

Learning Linux Shell Scripting

By : Ganesh Sanjiv Naik
3 (6)
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Learning Linux Shell Scripting

Learning Linux Shell Scripting

3 (6)
By: Ganesh Sanjiv Naik

Overview of this book

Linux is the most powerful and universally adopted OS. 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 reads this file and acts on commands as if they were typed on the keyboard. Learning Linux Shell Scripting covers Bash, GNU Bourne Again Shell, preparing you to work in the exciting world of Linux shell scripting. CentOS is a popular rpm-based stable and secured Linux distribution. Therefore, we have used CentOS distribution instead of Ubuntu distribution. Linux Shell Scripting is independent of Linux distributions, but we have covered both types of distros. We start with an introduction to the Shell environment and basic commands used. Next, we explore process management in Linux OS, real-world essentials such as debugging and perform Shell arithmetic fluently. You'll then take a step ahead and learn new and advanced topics in Shell scripting, such as decision making, starting up a system, and customizing a Linux environment. You will also learn about grep, stream editor, and AWK, which are very powerful text filters and editors. Finally, you'll get to grips with taking backup, using other language scripts in Shell Scripts as well as automating database administration tasks for MySQL and Oracle. By the end of this book, you will be able to confidently use your own shell scripts in the real world.
Table of Contents (17 chapters)
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Understanding variables

Let's learn about creating variables in a shell.

Declaring variables in Linux is very easy. We just need to use the variable name and initialize it with the required content.

$ person="Ganesh Naik"

To get the content of the variable, we need to add the prefix $ before the variable, for example:

    $ echo person    
person $ echo $person Ganesh Naik

The unset command can be used to delete the declared variable:

$ a=20$ echo $a$ unset a

The unset command will clear or remove the variable from the shell environment as well.

Here, the set command will show all variables declared in the shell:

$ person="Ganesh Naik"$ echo $person$ set

Here, using the declare command with the -x option will make it an environmental or global variable. We will find out more about environmental variables in the next section.

$ declare -x variable...

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