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  • Book Overview & Buying Linux Command Line and Shell Scripting Bible
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Linux Command Line and Shell Scripting Bible

Linux Command Line and Shell Scripting Bible - Third Edition

By : Richard Blum, Christine Bresnahan
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Linux Command Line and Shell Scripting Bible

Linux Command Line and Shell Scripting Bible

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)
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1
Introduction
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Introduction
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Who Should Read This Book
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How This Book Is Organized
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Minimum Requirements
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Where to Go from Here
2
Part I: The Linux Command Line
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Part I: The Linux Command Line
3
Chapter 1: Starting with Linux Shells
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Chapter 1: Starting with Linux Shells
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What Is Linux?
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Linux Distributions
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Summary
4
Chapter 2: Getting to the Shell
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Chapter 2: Getting to the Shell
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Reaching the Command Line
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Accessing CLI via a Linux Console Terminal
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Accessing CLI via Graphical Terminal Emulation
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Using the GNOME Terminal Emulator
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Using the Konsole Terminal Emulator
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Using the xterm Terminal Emulator
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Summary
5
Chapter 3: Basic bash Shell Commands
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Chapter 3: Basic bash Shell Commands
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Starting the Shell
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Using the Shell Prompt
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Interacting with the bash Manual
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Navigating the Filesystem
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Listing Files and Directories
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Handling Files
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Managing Directories
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Viewing File Contents
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Summary
6
Chapter 4: More bash Shell Commands
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Chapter 4: More bash Shell Commands
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Monitoring Programs
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Monitoring Disk Space
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Working with Data Files
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Summary
7
Chapter 5: Understanding the Shell
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Chapter 5: Understanding the Shell
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Exploring Shell Types
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Exploring Parent and Child Shell Relationships
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Understanding Shell Built-In Commands
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Summary
8
Chapter 6: Using Linux Environment Variables
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Chapter 6: Using Linux Environment Variables
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Exploring Environment Variables
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Setting User-Defined Variables
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Removing Environment Variables
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Uncovering Default Shell Environment Variables
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Setting the PATH Environment Variable
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Locating System Environment Variables
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Learning about Variable Arrays
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Summary
9
Chapter 7: Understanding Linux File Permissions
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Chapter 7: Understanding Linux File Permissions
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Linux Security
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Using Linux Groups
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Decoding File Permissions
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Changing Security Settings
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Sharing Files
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Summary
10
Chapter 8: Managing Filesystems
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Chapter 8: Managing Filesystems
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Exploring Linux Filesystems
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Working with Filesystems
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Managing Logical Volumes
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Summary
11
Chapter 9: Installing Software
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Chapter 9: Installing Software
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Package Management Primer
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The Debian-Based Systems
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The Red Hat–Based Systems
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Installing from Source Code
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Summary
12
Chapter 10: Working with Editors
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Chapter 10: Working with Editors
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Visiting the vim Editor
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Navigating the nano Editor
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Exploring the emacs Editor
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Exploring the KDE Family of Editors
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Exploring the GNOME Editor
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Summary
13
Part II: Shell Scripting Basics
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Part II: Shell Scripting Basics
14
Chapter 11: Basic Script Building
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Chapter 11: Basic Script Building
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Using Multiple Commands
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Creating a Script File
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Displaying Messages
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Using Variables
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Redirecting Input and Output
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Pipes
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Performing Math
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Exiting the Script
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Summary
15
Chapter 12: Using Structured Commands
chevron up
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Chapter 12: Using Structured Commands
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Working with the if-then Statement
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Exploring the if-then-else Statement
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Nesting ifs
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Trying the test Command
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Considering Compound Testing
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Working with Advanced if-then Features
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Considering the case Command
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Summary
16
Chapter 13: More Structured Commands
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Chapter 13: More Structured Commands
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The for Command
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The C-Style for Command
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The while Command
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The until Command
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Nesting Loops
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Looping on File Data
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Controlling the Loop
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Processing the Output of a Loop
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Practical Examples
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Summary
17
Chapter 14: Handling User Input
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Chapter 14: Handling User Input
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Passing Parameters
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Using Special Parameter Variables
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Being Shifty
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Working with Options
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Standardizing Options
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Getting User Input
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Summary
18
Chapter 15: Presenting Data
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Chapter 15: Presenting Data
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Understanding Input and Output
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Redirecting Output in Scripts
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Redirecting Input in Scripts
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Creating Your Own Redirection
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Listing Open File Descriptors
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Suppressing Command Output
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Using Temporary Files
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Logging Messages
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Practical Example
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Summary
19
Chapter 16: Script Control
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Chapter 16: Script Control
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Handling Signals
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Running Scripts in Background Mode
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Running Scripts without a Hang-Up
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Controlling the Job
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Being Nice
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Running Like Clockwork
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Summary
20
Part III: Advanced Shell Scripting
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Part III: Advanced Shell Scripting
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Chapter 17: Creating Functions
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Chapter 17: Creating Functions
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Basic Script Functions
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Returning a Value
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Using Variables in Functions
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Array Variables and Functions
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Function Recursion
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Creating a Library
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Using Functions on the Command Line
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Following a Practical Example
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Summary
22
Chapter 18: Writing Scripts for Graphical Desktops
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Chapter 18: Writing Scripts for Graphical Desktops
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Creating Text Menus
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Doing Windows
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Getting Graphic
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Summary
23
Chapter 19: Introducing sed and gawk
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Chapter 19: Introducing sed and gawk
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Manipulating Text
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Commanding at the sed Editor Basics
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Summary
24
Chapter 20: Regular Expressions
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Chapter 20: Regular Expressions
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What Are Regular Expressions?
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Defining BRE Patterns
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Extended Regular Expressions
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Regular Expressions in Action
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Summary
25
Chapter 21: Advanced sed
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Chapter 21: Advanced sed
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Looking at Multiline Commands
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Holding Space
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Negating a Command
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Changing the Flow
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Replacing via a Pattern
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Placing sed Commands in Scripts
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Creating sed Utilities
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Summary
26
Chapter 22: Advanced gawk
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Chapter 22: Advanced gawk
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Using Variables
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Working with Arrays
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Using Patterns
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Structured Commands
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Formatted Printing
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Built-In Functions
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User-Defined Functions
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Working through a Practical Example
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Summary
27
Chapter 23: Working with Alternative Shells
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Chapter 23: Working with Alternative Shells
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What Is the dash Shell?
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The dash Shell Features
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Scripting in dash
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The zsh Shell
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Parts of the zsh Shell
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Scripting with zsh
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Summary
28
Part IV: Creating Practical Scripts
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Part IV: Creating Practical Scripts
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Chapter 24: Writing Simple Script Utilities
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Chapter 24: Writing Simple Script Utilities
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Performing Archives
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Managing User Accounts
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Monitoring Disk Space
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Summary
30
Chapter 25: Producing Scripts for Database, Web, and E-Mail
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Chapter 25: Producing Scripts for Database, Web, and E-Mail
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Using a MySQL Database
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Using the Web
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Using E-Mail
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Summary
31
Chapter 26: Creating Fun Little Shell Scripts
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Chapter 26: Creating Fun Little Shell Scripts
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Sending a Message
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Obtaining a Quote
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Generating an Excuse
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Summary
32
End User License Agreement
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End User License Agreement
1
Appendix A: Quick Guide to bash Commands
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Appendix A: Quick Guide to bash Commands
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Reviewing Built-In Commands
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Looking at Common bash Commands
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Assessing Environment Variables
2
Appendix B: Quick Guide to sed and gawk
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Appendix B: Quick Guide to sed and gawk
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The sed Editor
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The gawk Program

Exploring the if-then-else Statement

In the if-then statement, you have only one option for whether a command is successful. If the command returns a non-zero exit status code, the bash shell just moves on to the next command in the script. In this situation, it would be nice to be able to execute an alternate set of commands. That's exactly what the if-then-else statement is for.

The if-then-else statement provides another group of commands in the statement:

if command
then
   commands
else
   commands
fi

When the command in the if statement line returns with a zero exit status code, the commands listed in the then section are executed, just as in a normal if-then statement. When the command in the if statement line returns a non-zero exit status code, the bash shell executes the commands in the else section.

Now you can copy and modify the test script to include an else section:

$ cp test3.sh test4.sh
$
$ nano test4.sh
$
$ cat test4.sh
#!/bin/bash
# testing the else section
#
testuser...
CONTINUE READING
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