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.

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Linux Command Line and Shell Scripting Bible - Third Edition
Richard Blum | Christine Bresnahan
Jan, 2015 | 816 pages
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Table of Contents (34 chapters)
Free Chapter
1
Introduction
Introduction
Who Should Read This Book
How This Book Is Organized
Minimum Requirements
Where to Go from Here
2
Part I: The Linux Command Line
Part I: The Linux Command Line
3
Chapter 1: Starting with Linux Shells
Chapter 1: Starting with Linux Shells
What Is Linux?
Linux Distributions
Summary
4
Chapter 2: Getting to the Shell
Chapter 2: Getting to the Shell
Reaching the Command Line
Accessing CLI via a Linux Console Terminal
Accessing CLI via Graphical Terminal Emulation
Using the GNOME Terminal Emulator
Using the Konsole Terminal Emulator
Using the xterm Terminal Emulator
Summary
5
Chapter 3: Basic bash Shell Commands
Chapter 3: Basic bash Shell Commands
Starting the Shell
Using the Shell Prompt
Interacting with the bash Manual
Navigating the Filesystem
Listing Files and Directories
Handling Files
Managing Directories
Viewing File Contents
Summary
6
Chapter 4: More bash Shell Commands
Chapter 4: More bash Shell Commands
Monitoring Programs
Monitoring Disk Space
Working with Data Files
Summary
7
Chapter 5: Understanding the Shell
Chapter 5: Understanding the Shell
Exploring Shell Types
Exploring Parent and Child Shell Relationships
Understanding Shell Built-In Commands
Summary
8
Chapter 6: Using Linux Environment Variables
Chapter 6: Using Linux Environment Variables
Exploring Environment Variables
Setting User-Defined Variables
Removing Environment Variables
Uncovering Default Shell Environment Variables
Setting the PATH Environment Variable
Locating System Environment Variables
Learning about Variable Arrays
Summary
9
Chapter 7: Understanding Linux File Permissions
Chapter 7: Understanding Linux File Permissions
Linux Security
Using Linux Groups
Decoding File Permissions
Changing Security Settings
Sharing Files
Summary
10
Chapter 8: Managing Filesystems
Chapter 8: Managing Filesystems
Exploring Linux Filesystems
Working with Filesystems
Managing Logical Volumes
Summary
11
Chapter 9: Installing Software
Chapter 9: Installing Software
Package Management Primer
The Debian-Based Systems
The Red Hat–Based Systems
Installing from Source Code
Summary
12
Chapter 10: Working with Editors
Chapter 10: Working with Editors
Visiting the vim Editor
Navigating the nano Editor
Exploring the emacs Editor
Exploring the KDE Family of Editors
Exploring the GNOME Editor
Summary
13
Part II: Shell Scripting Basics
Part II: Shell Scripting Basics
14
Chapter 11: Basic Script Building
Chapter 11: Basic Script Building
Using Multiple Commands
Creating a Script File
Displaying Messages
Using Variables
Redirecting Input and Output
Pipes
Performing Math
Exiting the Script
Summary
15
Chapter 12: Using Structured Commands
Chapter 12: Using Structured Commands
Working with the if-then Statement
Exploring the if-then-else Statement
Nesting ifs
Trying the test Command
Considering Compound Testing
Working with Advanced if-then Features
Considering the case Command
Summary
16
Chapter 13: More Structured Commands
Chapter 13: More Structured Commands
The for Command
The C-Style for Command
The while Command
The until Command
Nesting Loops
Looping on File Data
Controlling the Loop
Processing the Output of a Loop
Practical Examples
Summary
17
Chapter 14: Handling User Input
Chapter 14: Handling User Input
Passing Parameters
Using Special Parameter Variables
Being Shifty
Working with Options
Standardizing Options
Getting User Input
Summary
18
Chapter 15: Presenting Data
Chapter 15: Presenting Data
Understanding Input and Output
Redirecting Output in Scripts
Redirecting Input in Scripts
Creating Your Own Redirection
Listing Open File Descriptors
Suppressing Command Output
Using Temporary Files
Logging Messages
Practical Example
Summary
19
Chapter 16: Script Control
Chapter 16: Script Control
Handling Signals
Running Scripts in Background Mode
Running Scripts without a Hang-Up
Controlling the Job
Being Nice
Running Like Clockwork
Summary
20
Part III: Advanced Shell Scripting
Part III: Advanced Shell Scripting
21
Chapter 17: Creating Functions
Chapter 17: Creating Functions
Basic Script Functions
Returning a Value
Using Variables in Functions
Array Variables and Functions
Function Recursion
Creating a Library
Using Functions on the Command Line
Following a Practical Example
Summary
22
Chapter 18: Writing Scripts for Graphical Desktops
Chapter 18: Writing Scripts for Graphical Desktops
Creating Text Menus
Doing Windows
Getting Graphic
Summary
23
Chapter 19: Introducing sed and gawk
Chapter 19: Introducing sed and gawk
Manipulating Text
Commanding at the sed Editor Basics
Summary
24
Chapter 20: Regular Expressions
Chapter 20: Regular Expressions
What Are Regular Expressions?
Defining BRE Patterns
Extended Regular Expressions
Regular Expressions in Action
Summary
25
Chapter 21: Advanced sed
Chapter 21: Advanced sed
Looking at Multiline Commands
Holding Space
Negating a Command
Changing the Flow
Replacing via a Pattern
Placing sed Commands in Scripts
Creating sed Utilities
Summary
26
Chapter 22: Advanced gawk
Chapter 22: Advanced gawk
Using Variables
Working with Arrays
Using Patterns
Structured Commands
Formatted Printing
Built-In Functions
User-Defined Functions
Working through a Practical Example
Summary
27
Chapter 23: Working with Alternative Shells
Chapter 23: Working with Alternative Shells
What Is the dash Shell?
The dash Shell Features
Scripting in dash
The zsh Shell
Parts of the zsh Shell
Scripting with zsh
Summary
28
Part IV: Creating Practical Scripts
Part IV: Creating Practical Scripts
29
Chapter 24: Writing Simple Script Utilities
Chapter 24: Writing Simple Script Utilities
Performing Archives
Managing User Accounts
Monitoring Disk Space
Summary
30
Chapter 25: Producing Scripts for Database, Web, and E-Mail
Chapter 25: Producing Scripts for Database, Web, and E-Mail
Using a MySQL Database
Using the Web
Using E-Mail
Summary
31
Chapter 26: Creating Fun Little Shell Scripts
Chapter 26: Creating Fun Little Shell Scripts
Sending a Message
Obtaining a Quote
Generating an Excuse
Summary
32
End User License Agreement
End User License Agreement
Appendix A: Quick Guide to bash Commands
Appendix A: Quick Guide to bash Commands
Reviewing Built-In Commands
Looking at Common bash Commands
Assessing Environment Variables
Appendix B: Quick Guide to sed and gawk
Appendix B: Quick Guide to sed and gawk
The sed Editor
The gawk Program

Understanding Input and Output

So far, you've seen two methods for displaying the output from your scripts:

  • Displaying output on the monitor screen
  • Redirecting output to a file

Both methods produced an all-or-nothing approach to data output. There are times, however, when it would be nice to display some data on the monitor and other data in a file. For these instances, it comes in handy to know how Linux handles input and output so you can get your script output to the right place.

The following sections describe how to use the standard Linux input and output system to your advantage, to help direct script output to specific locations.

Standard file descriptors

The Linux system handles every object as a file. This includes the input and output process. Linux identifies each file object using a file descriptor. The file descriptor is a non-negative integer that uniquely identifies open files in a session. Each process is allowed to have up to nine open file descriptors at a time...

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