A Practical Guide to Linux(R) Commands, Editors, and Shell Programming

Mark G. Sobell is president of Sobell Associates Inc., a consulting firm that specializes in UNIX/Linux training, support, and custom software development. He is the author of many best-selling UNIX and Linux books and has more than twenty-five years of experience working with UNIX and Linux.

A Practical Guide to Linux® Commands, Editors, and Shell Programming explains how to work with the Linux operating system from the command line. The first few chapters quickly bring readers with little computer experience up to speed. The rest of the book is appropriate for more experienced computer users. This book does not describe a particular release or distribution of Linux but rather pertains to all recent versions of Linux.

Command line interface (CLI). In the beginning there was the command line (textual) interface (CLI), which enabled you to give Linux commands from the command line. There was no mouse or icons to drag and drop. Some programs, such as emacs, implemented rudimentary windows using the very minimal graphics available in the ASCII character set. Reverse video helped separate areas of the screen. Linux was born and raised in this environment.

Naturally all of the original Linux tools were invoked from the command line. The real power of Linux still lies in this environment, which explains why many Linux professionals work exclusively from the command line. Using clear descriptions and lots of examples, this book shows you how to get the most out of your Linux system using the command line interface.

Linux distributions. A Linux distribution comprises the Linux kernel, utilities, and application programs. Many distributions are available, including Debian, Red Hat, Fedora Core, SUSE, Mandriva (formerly Mandrake), KNOPPIX, and Slackware. Although the distributions differ from one another in various ways, all of them rely on the Linux kernel, utilities, and applications. This book is based on the code that is common to most distributions. As a consequence you can use it regardless of which distribution you are running.

Overlap. If you read A Practical Guide to Red Hat® Linux®: Fedora Core™ and Red Hat Enterprise Linux, Second Edition, or a subsequent edition, you will notice some overlap between that book and the one you are reading now. The introduction, the appendix on regular expressions, and the chapters on the utilities (Chapter 3 of this book--not Part V), the filesystem, and programming tools are very similar in the two books. The three chapters that cover the Bourne Again Shell (bash) have been expanded and rewritten for this text. Chapters that appear in this book and but not in A Practical Guide to Red Hat® Linux,® Second Edition, include those covering the vim and emacs editors, the TC Shell (tcsh), the gawk and sed languages, and Part V, which describes 80 of the most useful Linux utility programs in detail.

Audience. This book is designed for a wide range of readers. It does not require programming experience, although some experience using a general-purpose computer is helpful. It is appropriate for the following readers:

• Students taking a class in which they use Linux
• Power users who want to explore the power of Linux from command line
• Professionals who use Linux at work
• System administrators who need a deeper understanding of Linux and the tools that are available to them
• Computer science students who are studying the Linux operating system
• Programmers who need to understand the Linux programming environment
• Technical executives who want to get a grounding in Linux

Benefits. A Practical Guide to Linux® Commands, Editors, and Shell Programming gives you an in-depth understanding of how to use Linux from the command line. Regardless of your background, it offers the knowledge you need to get on with your work: You will come away from this book understanding how to use Linux, and this text will remain a valuable reference for years to come.

Features of This Book

This book is organized for ease of use in different situations. For example, you can read it from cover to cover to learn command line Linux from the ground up. Alternatively, once you are comfortable using Linux, you can use this book as a reference: Look up a topic of interest in the table of contents or index and read about it. Or, refer to one of the utilities covered in Part V, “Linux Utility Programs.” You can also think of this book as a catalog of Linux topics: Flip through the pages until a topic catches your eye. The book also includes many pointers to Web sites where you can get additional information: Consider the Web an extension of this book.

A Practical Guide to Linux® Commands, Editors, and Shell Programming offers the following features:

• Optional sections allow you to read the book at different levels, returning to more difficult material when you are ready to tackle it.
• Caution boxes highlight procedures that can easily go wrong, giving you guidance before you run into trouble.
• Tip boxes highlight places in the text where you can save time by doing something differently or when it may be useful or just interesting to have additional information.
• Security boxes point out ways that you can make a system more secure.
• The Supporting Web site will include corrections to the book, downloadable examples from the book, pointers to useful Web sites, and answers to even-numbered exercises.
• Concepts are illustrated by practical examples found throughout the book.
• The many useful URLs (Internet addresses) identify sites where you can obtain software and information.
• Chapter summaries review the important points covered in each chapter.
• Review exercises are included at the end of each chapter for readers who want to hone their skills. Answers to even-numbered exercises are available at www.sobell.com.
• Important GNU tools, including gcc, gdb, GNU Configure and Build System, make, gzip, and many others, are described in detail.
• Pointers throughout the book provide help in obtaining online documentation from many sources, including the local system and the Internet.

Contents

This section describes the information that each chapter covers and explains how that information can help you take advantage of the power of Linux. You may want to review the table of contents for more detail.

Chapter 1: Welcome to Linux

Presents background information on Linux. This chapter covers the history of Linux, explains how the GNU project helped Linux get started, and discusses some of Linux’s important features that distinguish it from other operating systems.

Part I: The Linux Operating System

Part I introduces Linux and gets you started using it.

TIP: Experienced Users May Want to Skim Part I
If you have used a UNIX/Linux system before, you may want to skim or skip some or all of the chapters in Part I. All readers should take a look at “Conventions Used in This Book,” which explains the typographic conventions that this book uses, and “Getting the Facts: Where to Find Documentation,” which points you toward both local and remote sources of Linux documentation.

Chapter 2: Getting Started

Explains the typographic conventions that this book uses to make explanations clearer and easier to read. This chapter provides basic information and explains how to log in, change your password, give Linux commands using the shell, and find system documentation.

Chapter 3: Command Line Utilities

Explains the command line interface (CLI) and briefly introduces more than 30 command line utilities. Working through this chapter gives you a feel for Linux and introduces some of the tools you will use day in and day out. The utilities covered in this chapter include

• grep, which searches through files for strings of characters;
• unix2dos, which converts Linux text files to Windows format;
• tar, which creates archive files that can hold many other files;
• bzip2 and gzip, which compress files so that they take up less space on disk and allow you to transfer them over a network more quickly; and
• diff, which displays the differences between two text files.

Chapter 4: The Linux Filesystem

Discusses the Linux hierarchical filesystem, covering files, filenames, pathnames, working with directories, access permissions, and hard and symbolic links. Understanding the filesystem allows you to organize your data so that you can find information quickly. It also enables you to share some of your files with other users while keeping other files private.

Chapter 5: The Shell

Explains how to use shell features to make your work faster and easier. All of the features covered in this chapter work with both the bash and tcsh. This chapter discusses

• Using command-line options to modify the way a command works;
• How a minor change in a command line can redirect input to a command to come from a file instead of the keyboard;
• How to redirect output from a command to go to a file instead of the screen;
• Using pipes to send the output of one utility directly to another utility...

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