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)

Ternary expressions

Ternary expressions are also known as conditional expressions. They are a special kind of expression that has three operands. In this expression, we use one expression's value to select one of two other expressions. It works the same way as in C language. Its syntax is as follows:

conditional exp1 ? Statement 1 : statement 2

If conditional expression exp1 returns true, then Statement1 gets executed; otherwise, statement2 gets executed. For example, here we use two variables and find largest number from two given numbers as follows:

$ vi ternary.awk

BEGIN {
p = 10; q=20
( p > q )? max=p: max =q
print max
}

$ awk -f ternary.awk

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

20 

In the following example, we prefix each line with a number, but we only print the numbers if the line is not blank. We use the NF built-in variable...