Book Image

Learning Linux Shell Scripting - Second Edition

By : Ganesh Sanjiv Naik
Book Image

Learning Linux Shell Scripting - Second Edition

By: Ganesh Sanjiv Naik

Overview of this book

Linux is the most powerful and universally adopted OS. 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 reads this file and acts on commands as if they were typed on the keyboard. Learning Linux Shell Scripting covers Bash, GNU Bourne Again Shell, preparing you to work in the exciting world of Linux shell scripting. CentOS is a popular rpm-based stable and secured Linux distribution. Therefore, we have used CentOS distribution instead of Ubuntu distribution. Linux Shell Scripting is independent of Linux distributions, but we have covered both types of distros. We start with an introduction to the Shell environment and basic commands used. Next, we explore process management in Linux OS, real-world essentials such as debugging and perform Shell arithmetic fluently. You'll then take a step ahead and learn new and advanced topics in Shell scripting, such as decision making, starting up a system, and customizing a Linux environment. You will also learn about grep, stream editor, and AWK, which are very powerful text filters and editors. Finally, you'll get to grips with taking backup, using other language scripts in Shell Scripts as well as automating database administration tasks for MySQL and Oracle. By the end of this book, you will be able to confidently use your own shell scripts in the real world.
Table of Contents (17 chapters)

Text filtering tools

Normally, shell scripting involves report generation, which will include processing various text files and filtering their output to finally produce the desired results. Let's start discussing the two Linux commands, namely more and less:

  • more: Sometimes we get a very large output on the screen for certain commands, which cannot be viewed completely in one screen. In such cases, we can use the more command to view the output text one page at a time. Add | more after the command, as follows:
    $ ll /dev | more

The | is called a pipe. You will learn more about it in the next chapters. In this command, pressing the spacebar will move the output on the screen one page at a time, or pressing Enter will move the screen one line at a time.

  • less: Instead of more, if you use less, it will show a screen containing the full text all at once. We can move forward...