Shell Programming: The Ultimate Beginner’s Guide to Learn Shell Step by Step

In recent years, the UNIX operating system has seen a huge boost in its popularity, especially with the emergence of Linux. For programmers and users of UNIX, this comes as no surprise: UNIX was designed to provide an environment that’s powerful yet easy to use.
One of the main strengths of UNIX is that it comes with a large collection of standard programs. These programs perform a wide variety of tasks from listing your files to reading email. Unlike other operating systems, one of the key features of UNIX is that these programs can be combined to perform complicated tasks and solve your problems.
One of the most powerful standard programs available in UNIX is the shell. The shell is a program that provides you with a consistent and easy-to-use environment for executing programs in UNIX. If you have ever used a UNIX system, you have interacted with the shell.
The main responsibility of the shell is to read the commands you type and then ask the UNIX kernel to perform these commands. In addition to this, the shell provides sophisticated programming constructs that enable you to make decisions, repeatedly execute commands, create functions, and store values in variables.

How This Book Is Organized
About the Examples
I assume that you have some familiarity with UNIX and know how to log in, create and edit files, and work with files and directories to a limited extent. If you haven’t used UNIX in a while or you aren’t familiar with one of these topics, don’t worry. The first part of this book reviews this material thoroughly.

This book is divided into three parts:

• Part I is an introduction to UNIX, the shell, and some common tools.
• Part II covers programming using the shell.
• Part III covers advanced topics in shell programming.

Part I consists of Chapters 1 through 6. The following material covered in the individual chapters:

• Chapter 1, “Shell Basics,” discusses several important concepts related to the shell and describes the different versions of the shell.
• Chapter 2, “Script Basics,” describes the process of creating and running a shell script. It also covers the login process and the different modes in which the shell executes.
• Chapters 3, “Working with Files,” and 4, “Working with Directories,” provide an overview of the commands used when working with files and directories. These chapters show you how to list the contents of a directory, view the contents of a file, and manipulate files and directories.
• Chapter 5, “Manipulating File Attributes,” introduces the concept of file attributes. It covers the different types of files along with modifying a file’s permissions. In UNIX every program runs as a process.
• Chapter 6, “Processes,” shows you how to start and stop a process. It also explains the term process ID and how you can view them. By this point, you should have a good foundation in the UNIX basics. This will enable you to start writing shell scripts that solve real problems using the concepts covered in Part II. Part II is the heart of this book, consisting of Chapters 7 through 18. It teaches you about all the tools available when programming in the shell.

Each chapter in this book includes complete syntax descriptions for the various commands along with several examples to illustrate the use of commands. The examples are designed to show you how to apply the commands to solve real problems. At the end of each chapter are a few questions that you can use to check your progress. Some of the questions are short answer while others require you to write scripts.