Book Image

Learning AWK Programming

By : Shiwang Kalkhanda
5 (1)
Book Image

Learning AWK Programming

5 (1)
By: Shiwang Kalkhanda

Overview of this book

AWK is one of the most primitive and powerful utilities which exists in all Unix and Unix-like distributions. It is used as a command-line utility when performing a basic text-processing operation, and as programming language when dealing with complex text-processing and mining tasks. With this book, you will have the required expertise to practice advanced AWK programming in real-life examples. The book starts off with an introduction to AWK essentials. You will then be introduced to regular expressions, AWK variables and constants, arrays and AWK functions and more. The book then delves deeper into more complex tasks, such as printing formatted output in AWK, control flow statements, GNU's implementation of AWK covering the advanced features of GNU AWK, such as network communication, debugging, and inter-process communication in the GAWK programming language which is not easily possible with AWK. By the end of this book, the reader will have worked on the practical implementation of text processing and pattern matching using AWK to perform routine tasks.
Table of Contents (11 chapters)

Basic regular expression construct

Regular expressions are made up of two types of characters: normal text characters, called literals, and special characters, such as the asterisk (*, +, ?, .), called metacharacters. There are times when you want to match a metacharacter as a literal character. In such cases, we prefix that metacharacter with a backslash (\), which is called an escape sequence.

The basic regular expression construct can be summarized as follows:

Here is the list of metacharacters, also known as special characters, that are used in building regular expressions:

\ ^ $ . [ ] | ( ) * + ?

The following table lists the remaining elements that are used in building a basic regular expression, apart from the metacharacters mentioned before:

Literal

A literal character (non-metacharacter ), such as A, that matches itself.

Escape...