Book Image

Learning Linux Shell Scripting

By : Ganesh Sanjiv Naik
Book Image

Learning Linux Shell Scripting

By: Ganesh Sanjiv Naik

Overview of this book

Linux is the one of the most powerful and universally adopted OSes. Shell is a program that gives the user direct interaction with the operating system. Scripts are collections of commands that are stored in a file. The shell can read this file and act on the commands as if they were typed on the keyboard. Shell scripting is used to automate day-to-day administration, and for testing or product development tasks. This book covers Bash, GNU Bourne Again SHell, preparing you to work in the exciting world of Linux shell scripting. We start with an introduction to the Shell environment and explain basic commands used in Shell. Next we move on to check, kill, and control the execution of processes in Linux OS. Further, we teach you about the filter tools available in Linux and explain standard output and standard errors devices. Then we will ensure you understand Shell’s interpretation of commands and get a firmer grasp so you use them in practice. Next, you’ll experience some real-world essentials such as debugging and perform Shell arithmetic fluently. Then you’ll take a step ahead and learn new and advanced topics in Shell scripting, such as starting up a system and customizing a Linux system. Finally, you’ll get to understand the capabilities of scripting and learn about Grep, Stream Editor, and Awk.
Table of Contents (20 chapters)
Learning Linux Shell Scripting
Credits
About the Author
Acknowledgments
About the Reviewers
www.PacktPub.com
Preface
Index

Using awk


awk is a program, which has its own programming language for performing data processing and to generate reports.

The GNU version of awk is gawk.

awk processes data, which can be received from a standard input, input file, or as the output of any other command or process.

awk processes data similar to sed, such as lines by line. It processes every line for the specified pattern and performs specified actions. If pattern is specified, then all the lines containing specified patterns will be displayed. If pattern is not specified, then the specified actions will be performed on all the lines.

The meaning of awk

The name of the program awk is made from the initials of three authors of the language, namely Alfred Aho, Peter Weinberger and Brian Kernighan. It is not very clear why they selected the name awk instead of kaw or wak!

Using awk

The following are different ways to use awk:

  • Syntax while using only pattern:

    $ awk 'pattern' filename
    

    In this case, all the lines containing pattern will...