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

Pattern searching using grep


The g/RE/p stands for globally search for the regular expression (RE) and print out the line.

Return status – success 0, pattern not found 1, file not found 2.

$  ps -ef | grep root

The preceding command will show all processes running currently whose user ID is "root".

$  ll /proc | grep "cpuinfo"

The preceding command will show the file with the name cpuinfo from the /proc directory.

$  grep –lir "text" *   // only file names  //   
$ grep –ir  "text" dir_name   // show lines of files //

We will try the following commands on the love.txt file:

Metacharacter

Function

Example

Description

^

Beginning-of-line anchor

'^mango'

Will display all lines beginning with mango

$

End-of-line anchor

'mango'$'

Will display all lines ending with mango

.

Matches single character

'm..o'

Will display lines containing m, followed by two characters, followed by an o

*

Matches zero or more characters preceding the asterisk

'*mango'

Will display...