Hello! AWK

Awk is a powerful tool in the commandline used for processing the rows and columns of a flat texy file. Awk has built in string functions and associative arrays. Awk supports most of the operators, conditional blocks, and loops available in C language. You may want to know, what Awk stands for? It comes from the surnames of its authors “Aho, Weinberger, and Kernighan”. AWK was created at Bell Labs in the 1970s. It is pronounced the same as the name of a bird called auk. The GNU implementation of awk is called gawk.

This tutorial will give you just enough knowledge to read and understand this book, to be a master on AWK, you need to explore relevant literature referenced at end of this book.

The AWK language is a fully data-driven scripting language consisting of a set of actions to be taken against streams of textual data - either run directly on files or used as part of a pipeline for purposes of extracting or transforming text, such as producing formatted reports.

The very basic syntax of AWK:

awk 'BEGIN {start-action} {action} END {stop-action}' filename

Note that the actions in the begin block are performed before processing the file and the actions in the end block are performed after processing the file. The rest of the actions are performed while processing the file!

It can be also written as:

awk '/search pattern1/ {Actions}
     /search pattern2/ {Actions}' file

In the above AWK syntax:

• search pattern is a regular expression;
• Actions are the statement(s) to be performed;
• several patterns and actions are possible in AWK;
• a file is an input file; and
• single quotes around program is to avoid shell not to interpret any of its special characters.