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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 Web page 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 and pipes.

Implementations of the awk language are available for many different computing environments. This Web page, while describing the awk language in general, also describes the particular implementation of awk called gawk (which stands for "GNU awk"). gawk runs on a broad range of Unix systems, ranging from 80386 PC-based computers up through large-scale systems, such as Crays. gawk has also been ported to Mac OS X, MS-DOS, Microsoft Windows (all versions) and OS/2 PCs, Atari and Amiga microcomputers, BeOS, Tandem D20, and VMS.

• History: The history of gawk and awk.
• Names: What name to use to find awk.
• This Manual: Using this Web page. Includes sample input files that you can use.
• Conventions: Typographical Conventions.
• Manual History: Brief history of the GNU project and this Web page.
• How To Contribute: Helping to save the world.
• Acknowledgments: Acknowledgments.

Footnotes

1. These commands are available on POSIX-compliant systems, as well as on traditional Unix-based systems. If you are using some other operating system, you still need to be familiar with the ideas of I/O redirection and pipes.