Book Image

Learning Linux Shell Scripting - Second Edition

By : Ganesh Sanjiv Naik
Book Image

Learning Linux Shell Scripting - Second Edition

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)

Passing arguments or parameters to functions

In certain situations, we may need to pass arguments or parameters to functions.
In such situations, we can pass arguments as follows.

Calling the script with command-line parameters is as follows:

    $ name arg1 arg2 arg3 . . .
  

Let's type a function as follows:

    $  hello() { echo "Hello $1, let us be a friend."; }
  

Call the function in the command line as follows:

    $ hello Ganesh
  

This should produce the following output:

    Hello Ganesh, let us be a friend
  

Let's write the script function_07.sh. In this script, we pass command-line parameters to the script as well as the function:

#!/bin/bash 
quit() 
{ 
         exit 
} 
ex() 
{ 
    echo $1 $2 $3 
} 
ex Hello hai bye     # Function ex with three arguments 
ex World             # Function ex with one argument 
echo $1        # First argument passed...