Effective awk Programming, 3rd Edition

Preface

Several 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.

The GNU implementation of awk is called gawk; it is fully compatible with the System V Release 4 version of awk. gawk is also compatible with the POSIX specification of the awk language. This means that all properly written awk programs should work with gawk. Thus, we usually don’t distinguish between gawk and other awk implementations.

Using awk allows you to:

• Manage small, personal databases

• Generate reports

• Validate data

• Produce indexes and perform other document preparation tasks

• Experiment with algorithms that you can adapt later to other computer languages

In addition, gawk provides facilities that make it easy to:

• Extract bits and pieces of data for processing

• Sort data

• Perform simple network communications

This book teaches you about the awk language and how you can use it effectively. You should already be familiar with basic system commands, such as cat and ls,^[1] as well as basic shell facilities, such as input/output (I/O) redirection ...