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  • Book Overview & Buying Mastering Linux Shell Scripting
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Mastering Linux Shell Scripting

Mastering Linux Shell Scripting

By : Andrew Mallett
3.8 (22)
Buy this Book
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Mastering Linux Shell Scripting

Mastering Linux Shell Scripting

3.8 (22)
By: Andrew Mallett
Buy this Book

Overview of this book

Shell scripting is a quick method to prototype a complex application or a problem by automating tasks when working on Linux-based systems. Using both simple one-line commands and command sequences complex problems can be solved with ease, from text processing to backing up sysadmin tools. In this book, you’ll discover everything you need to know to master shell scripting and make informed choices about the elements you employ. Get to grips with the fundamentals of creating and running a script in normal mode, and in debug mode. Learn about various conditional statements' code snippets, and realize the power of repetition and loops in your shell script. Implement functions and edit files using the Stream Editor, script in Perl, program in Python – as well as complete coverage of other scripting languages to ensure you can choose the best tool for your project.
Table of Contents (17 chapters)
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Preface
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Preface
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Who this book is for
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What this book covers
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To get the most out of this book
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Get in touch
Lock Free Chapter
1
The What and Why of Scripting with Bash
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The What and Why of Scripting with Bash
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Technical requirements
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Types of Linux shells
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What is bash scripting?
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The bash command hierarchy
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Preparing text editors for scripting
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Creating and executing scripts
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Declaring variables
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Variable scope
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Command substitution
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Debugging your scripts
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Summary
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Questions
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Further reading
2
Creating Interactive Scripts
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Creating Interactive Scripts
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Technical requirements
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Using echo with options
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Basic script using read
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Script comments
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Enhancing scripts with read prompts
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Limiting the number of entered characters
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Controlling the visibility of the entered text
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Passing options
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Try to be standard
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Enhancing learning with simple scripts
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Summary
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Questions
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Further reading
3
Conditions Attached
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Conditions Attached
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Technical requirements
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Simple decision paths using command-line lists
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Verifying user input with lists
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Using the test shell built-in
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Creating conditional statements using if
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Extending if with else
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Test command with the if command
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More conditions with elif
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Using case statements
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Recipe – building a frontend with grep
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Summary
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Questions
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Further reading
4
Creating Code Snippets
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Creating Code Snippets
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Technical requirements
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Abbreviations
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Using code snippets
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Creating snippets using VS Code
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Summary
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Questions
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Further reading
5
Alternative Syntax
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Alternative Syntax
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Technical requirement
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Recapping the test command
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Providing parameter defaults
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When in doubt – quote!
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Advanced tests using [[
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Arithmetic operations using ((
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Summary
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Questions
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Further reading
6
Iterating with Loops
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Iterating with Loops
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Technical requirement
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for loops
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Advanced for loops
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The IFS
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Counting directories and files
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C-style for loops
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Nested loops
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Redirecting loop output
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while loops and until loops
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Reading input from files
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Creating operator menus
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Summary
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Questions
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Further reading
7
Creating Building Blocks with Functions
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Creating Building Blocks with Functions
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Technical requirements
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Introducing functions
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Passing parameters to functions
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Variable scope
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Returning values from functions
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Recursive functions
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Using functions in menus
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Summary
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Questions
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Further reading
8
Introducing the Stream Editor
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Introducing the Stream Editor
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Technical requirements
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Using grep to display text
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Understanding the basics of sed
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Other sed commands
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Multiple sed commands
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Summary
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Questions
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Further reading
9
Automating Apache Virtual Hosts
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Automating Apache Virtual Hosts
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Technical requirements
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Apache name-based Virtual Hosts
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Automating virtual host creation
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Summary
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Questions
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Further reading
10
AWK Fundamentals
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AWK Fundamentals
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Technical requirements
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The history behind AWK
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Displaying and filtering content from files
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AWK variables
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Conditional statements
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Formatting output
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Further filtering to display users by UID
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AWK control files
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Summary
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Questions
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Further reading
11
Regular Expressions
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Regular Expressions
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Technical requirements
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Regular expression engines
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Defining BRE patterns
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Defining ERE patterns
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Using grep
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Summary
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Questions
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Further reading
12
Summarizing Logs with AWK
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Summarizing Logs with AWK
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Technical requirements
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The HTTPD log file format
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Displaying data from web logs
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Displaying the highest ranking IP address
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Displaying the browser data
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Working with email logs
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Summary
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Questions
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Further reading
13
A Better lastlog with AWK
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A Better lastlog with AWK
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Technical requirements
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Using AWK ranges to exclude data
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Conditions based on the number of fields
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Manipulating the AWK record separator to report on XML data
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Summary
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Questions
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Further reading
14
Using Python as a Bash Scripting Alternative
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Using Python as a Bash Scripting Alternative
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Technical requirements
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What is Python?
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Saying Hello World the Python way
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Pythonic arguments
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Supplying arguments
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Counting arguments
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Significant whitespace
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Reading user input
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Using Python to write to files
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String manipulation
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Summary
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Questions
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Further reading
15
Assessments
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Assessments
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Chapter 1
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Chapter 2
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Chapter 3
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Chapter 4
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Chapter 5
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Chapter 6
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Chapter 7
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Chapter 8
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Chapter 9
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Chapter 10
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Chapter 11
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Chapter 12
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Chapter 13
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Chapter 14
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Other Books You May Enjoy
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Other Books You May Enjoy
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Conventions

In this book, you will find a number of text styles that distinguish between different kinds of information. Here are some examples of these styles and an explanation of their meaning.

Code words in text, database table names, folder names, filenames, file extensions, pathnames, dummy URLs, user input, and Twitter handles are shown as follows: "We again see that the basename is evaluated first, but we do not see the more detailed steps involved in running that command."

A block of code is set as follows:

#!/bin/bash
echo "You are using $0"
echo "Hello $*"
exit 0

When we wish to draw your attention to a particular part of a code block, the relevant lines or items are set in bold:

#!/bin/bash
echo "You are using $0"
echo "Hello $*"
exit 0

Any command-line input or output is written as follows:

$ bash -x $HOME/bin/hello2.sh fred

New terms and important words are shown in bold. Words that you see on the screen, for example, in menus or dialog boxes, appear in the text like this: "Clicking the Next button moves you to the next screen."

Note

Warnings or important notes appear in a box like this.

Tip

Tips and tricks appear like this.

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Programming languages
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