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)

Numeric constants

A numeric constant stands for a number. It can be an integer, a decimal fraction, or a number in an exponential notation. Some examples of numeric constant values are as follows:

  • 100
  • 1.10
  • 1.05e+2
  • 1.05e-1

Any nonzero numeric value in AWK is true in the case of expression evaluation, and zero is false. For example:

$ vi numeric.awk

if ( 1 )
print "numeric 1 "
if ( 1.234 )
print "numeric 1.234"
if ( 1.234e )
print "numeric 1.234e"
if ( 0 )
print "false"

$ awk -f numeric.awk

The output of the execution of the preceding code is as follows:

numeric 1 
numeric 1.234
numeric 1.234e