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
Credits
About the Authors
About the Reviewers
www.PacktPub.com
Preface
Index

Searching and mining a text inside a file with grep


Searching inside a file is an important use case in text processing. We may need to search through thousands of lines in a file to find out some required data, by using certain specifications. This recipe will help you learn how to locate data items of a given specification from a pool of data.

How to do it...

The grep command is the magic Unix utility for searching in text. It accepts regular expressions, and can produce output in various formats. Additionally, it has numerous interesting options. Let's see how to use them:

  1. To search for lines of text that contain the given pattern:

    $ grep pattern filename
    this is the line containing pattern
    

    Or:

    $ grep "pattern" filename
    this is the line containing pattern
    
  2. We can also read from stdin as follows:

    $ echo -e "this is a word\nnext line" | grep word 
    this is a word
    
  3. Perform a search in multiple files by using a single grep invocation, as follows:

    $ grep "match_text" file1 file2 file3 ... 
    
  4. We can...