Book Image

Linux Shell Scripting Cookbook, Second Edition - Second Edition

Book Image

Linux Shell Scripting Cookbook, Second Edition - Second Edition

Overview of this book

The shell remains one of the most powerful tools on a computer system — yet a large number of users are unaware of how much one can accomplish with it. Using a combination of simple commands, we will see how to solve complex problems in day to day computer usage.Linux Shell Scripting Cookbook, Second Edition will take you through useful real-world recipes designed to make your daily life easy when working with the shell. The book shows the reader how to effectively use the shell to accomplish complex tasks with ease.The book discusses basics of using the shell, general commands and proceeds to show the reader how to use them to perform complex tasks with ease.Starting with the basics of the shell, we will learn simple commands with their usages allowing us to perform operations on files of different kind. The book then proceeds to explain text processing, web interaction and concludes with backups, monitoring and other sysadmin tasks.Linux Shell Scripting Cookbook, Second Edition serves as an excellent guide to solving day to day problems using the shell and few powerful commands together to create solutions.
Table of Contents (16 chapters)
Linux Shell Scripting Cookbook
About the Authors
About the Reviewers

Using awk for advanced text processing

awk is a tool designed to work with data streams. It is very interesting, as it can operate on columns and rows. It supports many built-in functionalities, such as arrays and functions, in the C programming language. Its biggest advantage is its flexibility.

Getting ready...

The structure of an awk script is as follows:

awk ' BEGIN{  print "start" } pattern { commands } END{ print "end" } file

The awk command can read from stdin also.

An awk script usually consists of three parts—BEGIN, END, and a common statements block with the pattern match option. The three of them are optional and any of them can be absent in the script.

How to do it…

Let's write a simple awk script enclosed in single quotes or double quotes, as follows:

awk 'BEGIN { statements } { statements } END { end statements }'

Or, alternately, use the following command:

awk "BEGIN { statements } { statements } END { end statements }"

For example:

$ awk 'BEGIN { i=0 } { i++ } END{ print i}' filename...