everal kinds of tasks occur repeatedly when working with text files. You might want to extract certain lines and discard the rest. Or you may need to make changes wherever certain patterns appear, but leave the rest of the file alone. Writing single-use programs for these tasks in languages such as C, C++, or Pascal is time-consuming and inconvenient. Such jobs are often easier with awk. The awk utility interprets a special-purpose programming language that makes it easy to handle simple data-reformatting jobs.

This text is a brief description of the features that are present in the Bash shell (version 3.2, 28 September 2006).

This is Edition 3.2, last updated 28 September 2006, of The GNU Bash Reference Manual, for Bash, Version 3.2.

Everybody working on a UNIX or UNIX-like system who wants to make life easier on themselves, power users and sysadmins alike, can benefit from reading this book. Readers who already have a grasp of working the system using the command line will learn the ins and outs of shell scripting that ease execution of daily tasks. System administration relies a great deal on shell scripting; common tasks are often automated using simple scripts. This document is full of examples that will encourage you to write your own and that will inspire you to improve on existing scripts.

wk is a programming language that gets its name from the 3 people who invented it (Aho, Weinberger, and Kernighan). Because it was developed on a Unix operating system, its name is usually printed in lower-case ("awk") instead of capitalized ("Awk"). awk is distributed as free software, meaning that you don't have to pay anything for it and you can get the source code to build awk yourself  .

Table of Contents
Part 1. Introduction

1. Why Shell Programming?
2. Starting Off With a Sha-Bang

Part 2. Basics

3. Special Characters
4. Introduction to Variables and Parameters
5. Quoting
6. Exit and Exit Status
7. Tests
8. Operations and Related Topics

Part 3. Beyond the Basics

9. Variables Revisited
10. Loops and Branches
11. Command Substitution
12. Arithmetic Expansion
13. Recess Time

Part 4. Commands

14. Internal Commands and Builtins