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Preface

Preface

Unix is one of the most powerful and widely used operating systems. It was conceived at AT&T's Bell Laboratories during early 1970s. Among many who fostered this operating system, particularly at the early stages, the contribution of the University of California at Berkeley is notable. Since then, it has grown in strength day by day. The sheer existence of this operating system over the past three decades itself speaks for its strength. It offers word-processing capability, networking facility, information retrieval and processing, and much more. Although powerful, it was not popular among users initially because it was developed for researchers by researchers, had trade restrictions, and also lacked a user-friendly device.

The addition of a GUI in the form of X-Window System and the availability of one of its free-of-cost versions called Linux during the 1990s, along with the falling prices of hardware, has resulted in expanding its user base.

Chapter 1 begins with a brief discussion on the history of the Unix development, identifies its salient features and important components, gives the meaning of Unix commands, and also discusses some of the basic Unix commands. Processes of organizing and accessing files are discussed in Chapter 2. It also deals with the commands that are used to navigate a Unix file system as well as some file handling commands.

Unix files have many attributes. These attributes are discussed in Chapter 3. Also included in this chapter is a discussion on how attributes of a file can be known and manipulated.

Piping and the concept of standard I/O and redirection are the topics that are chiefly discussed in Chapter 4. This chapter also gives the meaning of a filter and deals with two of the more useful filters—the sort and the tr commands.

Unix has different types of editors such as ed, ex, vi, vim and emacs. Chapter 5 deals with one of the very popular editors, vi. Regular expressions and the whole range of grep family of commands and the stream editor, sed have been discussed in Chapter 6.

The concept of process, the mechanism of the creation of a process, and certain essential commands that deal with processes have been discussed in Chapter 7. Also included in this chapter is a discussion on signals and their usage in handling processes.

Chapter 8 discusses shell programming. The shell variables, positional parameters, branching and loop control structures along with essential commands that aid in writing and successful execution of shell scripts are also discussed in detail.

Chapter 9 is a discussion on awk, a C-style programming language primarily used for information retrieval and report generation tasks. Some simple and useful awk scripts are also included in this chapter.

Chapter 10 deals with some of the basic communication tools that are available in Unix.

Chapter 11 explains the essentials of Perl, one of the excellent languages which has the combined powers of many other powerful Unix tools such as the shell, the grep, and awk.

Chapter 12 gives a brief overview of system administration, specifically at an introductory level, and also talks about the way in which a Unix file system stores and maintains all of its relevant information on a physical device like a hard disk.

The contents of this book have been selected such that it could be taught in a semester for four credits as a first course at the degree level. All the discussions in this book chiefly refer to the Bourne shell. However, certain features like background processes, repeating commands using the history facility and aliases that are not found in the Bourne shell have also been discussed. Brief references to Linux have been made at all the possible places. All the scripts presented in this book have been tested successfully.

This book introduces the basic concepts of a Unix operating system in general and also gives a sufficient knowledge on writing scripts with different Unix languages such as awk, perl and shell. This book assumes prior working knowledge in the C programming language.

M. G. Venkateshmurthy

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