Chapter 1, Getting Started and Working with Shell Scripting, you will learn different ways to write and run Shell scripts. You will also learn ways to handle files and directories, and you will learn about working with permissions.

Chapter 2, Drilling Deep into Process Management, Job Control, and Automation, you will learn about basic process management. You will learn about command ps and job management using commands such as jobs, fg, bg, kill, and pkill. Later on, you will learn about process monitoring tools: top, iostat, vmstat and sar.

Chapter 3, Using Text Processing and Filters in Your Scripts, you will learn about using more, less, head, and tail commands. You will also learn text processing tools such as, cut, paste, comm, and uniq. You will learn about standard input, output, and error. Later on, you will learn about metacharacters and pattern matching using vi and grep.

Chapter 4, Working with Commands, you will learn about how shell interprets any command entered on the command line. You will also learn command substitution, separators, and pipes in detail.

Chapter 5, Exploring Expressions and Variables, you will learn about variables—environment variables. This will include how to export environment variables, set, shift, read-only variables, command-line arguments, and about creating and handling arrays.

Chapter 6, Neat Tricks with Shell Scripting, you will learn about debugging, the here operator, interactive Shell scripts for taking input from the keyboard, and file handling.

Chapter 7, Performing Arithmetic in Shell Scripts, you will learn about doing arithmetic operations in various ways, such as using declare, let, expr, and arithmetic expressions. You will also learn about representing numbers in different bases, such as hex, octal, and binary. You will learn about using the bc utility for doing floating point or fractional arithmetic.

Chapter 8, Automating Decision Making in Scripts, you will learn about using decision making in scripts working with test, if…else, and switching case. You will also use select for loop with menu. For repeating tasks such as processing lists, you will learn about using for loop, while loop and do while. You will also learn about how to control loops using break and continue statements.

Chapter 9, Working with Functions, we will understand about functions in Shell scripts. You will learn about the definition and display of functions by removing the function from the shell. You will also learn about passing arguments to functions, sharing data between functions, declaring local variables in functions, returning results from functions, and running functions in background. You will finally learn about using source and . commands. We will use these commands to use the library of functions.

Chapter 10, Using Advanced Functionality in Scripts, you will learn about using traps and signals. You will also learn about creating menus with the help of the dialog utility.

Chapter 11, System Startup and Customizing a Linux System, you will learn about Linux system startup from power on until the user login and how to customize a Linux system environment.

Chapter 12, Pattern Matching and Regular Expressions with sed and awk, you will learn about regular expressions and using sed (stream editor) and awk for text processing. You will learn about the usage of various commands and options along with a lot of examples for using sed and awk.

Any computer that has Linux OS installed on it will be sufficient for learning all the topics discussed in this book. I have personally tested all the commands and scripts in Ubuntu 12.10 distribution.

While learning, if you find that any utility has not installed alongside Ubuntu or any Debian-based distribution, then enter the following command to install this utility:

$ sudo apt-get update
$ sudo apt-get install package-name

The Internet should be available for the previous commands to run.

In Red Hat or any other rpm-based distribution, enter the following commands:

$ sudo yum update
$ sudo yum install package-name

If the Internet is connected, then using these commands, you can install any command or utility that is not already installed.

This book is for the readers that are proficient at working with Linux, and who want to learn about Shell scripting to improve their efficiency and practical skills. The following are a few examples where we can use skills learned in this book:

In this book, you will find a number of text styles that distinguish between different kinds of information. Here are some examples of these styles and an explanation of their meaning.

Code words in text, database table names, folder names, filenames, file extensions, pathnames, dummy URLs, user input, and Twitter handles are shown as follows: "In the output, 4d3 tells us that line number 4 is deleted in file2. Similarly, the change command will show us changes in the file as well."

A block of code is set as follows:

#!/bin/bash
# This is comment line
echo "Hello World"
ls
date

When we wish to draw your attention to a particular part of a code block, the relevant lines or items are set in bold:

$ expr 4 * 10
expr: syntax error
With command expr, we cannot use * for multiplication. We need to use \* for multiplication.
$ expr "4 * 10"
4 * 10
$ expr 4 \* 10
40

Any command-line input or output is written as follows:

$ sed '1,3d' datafile >  tempfile
$ awk -F: '/Marie/{print $1, $2}' people1.txt

New terms and important words are shown in bold.

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