Book Image

Linux Command Line and Shell Scripting Bible - Third Edition

By : Richard Blum, Christine Bresnahan
Book Image

Linux Command Line and Shell Scripting Bible - Third Edition

By: Richard Blum, Christine Bresnahan

Overview of this book

The Linux command line enables you to type specific shell commands directly into the system to manipulate files and query system resources. Command line statements can be combined into short programs called shell scripts, a practice increasing in popularity due to its usefulness in automation. Linux is a robust system with tremendous potential, and Linux Command Line and Shell Scripting Bible opens the door to new possibilities. Linux Command Line and Shell Scripting Bible is your essential Linux guide. It contains new functional examples that are fully updated to align with the latest Linux features. Beginning with command line fundamentals, the book moves into shell scripting and shows you the practical application of commands in automating frequently performed functions. This book is a complete guide providing detailed instruction and expert advice working within this aspect of Linux. Whether used as a tutorial or as a quick reference, this book contains information that every Linux user should know.
Table of Contents (34 chapters)
2
Part I: The Linux Command Line
13
Part II: Shell Scripting Basics
20
Part III: Advanced Shell Scripting
28
Part IV: Creating Practical Scripts
32
End User License Agreement

Controlling the Loop

You might be tempted to think that after you start a loop, you're stuck until the loop finishes all its iterations. This is not true. A couple of commands help us control what happens inside of a loop:

  • The break command
  • The continue command

Each command has a different use in how to control the operation of a loop. The following sections describe how you can use these commands to control the operation of your loops.

The break command

The break command is a simple way to escape a loop in progress. You can use the break command to exit any type of loop, including while and until loops.

You can use the break command in several situations. This section shows each of these methods.

Breaking out of a single loop

When the shell executes a break command, it attempts to break out of the loop that's currently processing:

 $ cat test17
 #!/bin/bash
 # breaking out of a for loop
 for var1 in 1 2 3 4 5 6 7 8 9 10
 do
    if [ $var1 -eq 5 ]
    then
       break
...