Effective awk Programming,3rd Edition, focuses entirely on awk, exploring it in the greatest depth of the three awk titles we carry. It's an excellent companion piece to the more broadly focused second edition.

This book provides complete coverage of the gawk 3.1 language as well as the most up-to-date coverage of the POSIX standard for awk available anywhere. Author Arnold Robbins clearly distinguishes standard awk features from GNU awk (gawk)-specific features, shines light into many of the "dark corners" of the language (areas to watch out for when programming), and devotes two full chapters to example programs. A brand new chapter is devoted to TCP/IP networking with gawk. He includes a summary of how the awk language evolved.

The book also covers:

• Internationalization of gawk
• Interfacing to i18n at the awk level
• Two-way pipes
• TCP/IP networking via the two-way pipe interface
• The new PROCINFO array, which provides information about running gawk
• Profiling and pretty-printing awk programs
• Dynamically adding built-in functions at run time

In addition to covering the awk language, this book serves as the official "User's Guide" for the GNU implementation of awk (gawk), describing in an integrated fashion the extensions available to the System V Release 4 version of awk that are also available in gawk.

As the official gawk User's Guide, this book will also be available electronically, and can be freely copied and distributed under the terms of the Free Software Foundation's Free Documentation License (FDL). A portion of the proceeds from sales of this book will go to the Free Software Foundation to support further development of free and open source software.

Table of Contents

Foreword

Preface

PART 1: The awk Language and gawk

Chapter 1. Getting Started with awk
   How to Run awk Programs
   Datafiles for the Examples
   Some Simple Examples
   An Example with Two Rules
   A More Complex Example
   awk Statements Versus Lines
   Other Features of awk
   When to Use awk

Chapter 2. Regular Expressions
   How to Use Regular Expressions
   Escape Sequences
   Regular Expression Operators
   Using Character Lists
   gawk-Specific Regexp Operators
   Case Sensitivity in Matching
   How Much Text Matches?
   Using Dynamic Regexps

Chapter 3. Reading Input Files
   How Input Is Split into Records
   Examining Fields
   Non-constant Field Numbers
   Changing the Contents of a Field
   Specifying How Fields Are Separated
   Reading Fixed-Width Data
   Multiple-Line Records
   Explicit Input with getline

Chapter 4. Printing Output
   The print Statement
   Examples of print Statements
   Output Separators
   Controlling Numeric Output with print
   Using printf Statements for Fancier Printing
   Redirecting Output of print and printf
   Special Filenames in gawk
   Closing Input and Output Redirections

Chapter 5. Expressions
   Constant Expressions
   Using Regular Expression Constants
   Variables
   Conversion of Strings and Numbers
   Arithmetic Operators
   String Concatenation
   Assignment Expressions
   Increment and Decrement Operators
   True and False in awk
   Variable Typing and Comparison Expressions
   Boolean Expressions
   Conditional Expressions
   Function Calls
   Operator Precedence (How Operators\ Nest)

Chapter 6. Patterns, Actions, and Variables
   Pattern Elements
   Using Shell Variables in Programs
   Actions
   Control Statements in Actions
   Built-in Variables

Chapter 7. Arrays in awk
   Introduction to Arrays
   Referring to an Array Element
   Assigning Array Elements
   Basic Array Example
   Scanning All Elements of an Array
   The delete Statement
   Using Numbers to Subscript Arrays
   Using Uninitialized Variables as Subscripts
   Multidimensional Arrays
   Scanning Multidimensional Arrays
   Sorting Array Values and Indices with gawk

Chapter 8. Functions
   Built-in Functions
   User-Defined Functions

Chapter 9. Internationalization with gawk
   Internationalization and Localization
   GNU gettext
   Internationalizing awk Programs
   Translating awk Programs
   A Simple Internationalization Example
   gawk Can Speak Your Language

Chapter 10. Advanced Features of gawk
   Allowing Nondecimal Input Data
   Two-Way Communications with\ Another\ Process
   Using gawk for Network Programming
   Using gawk with BSD Portals
   Profiling Your awk Programs

Chapter 11. Running awk and gawk
   Invoking awk
   Command-Line Options
   Other Command-Line Arguments
   The AWKPATH Environment Variable
   Obsolete Options and/or Features
   Known Bugs in gawk

PART 2: Using awk and gawk

Chapter 12. A Library of awk Functions
   Naming Library Function Global\ Variables
   General Programming
   Datafile Management
   Processing Command-Line Options
   Reading the User Database
   Reading the Group Database

Chapter 13. Practical awk Programs
   Running the Example Programs
   Reinventing Wheels for Fun and Profit
   A Grab Bag of awk Programs

Chapter 14. Internetworking with gawk
   Networking with gawk
   Some Applications and Techniques
   Related Links

PART 3: Appendixes

Appendix A. The Evolution of the awk Language

Appendix B. Installing gawk

Appendix C. Implementation Notes

Appendix D. Basic Programming Concepts

Appendix E. GNU General Public License

Appendix F. GNU Free Documentation License

Glossary

Index