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The Ultimate Linux Shell Scripting Guide

The Ultimate Linux Shell Scripting Guide

By : Donald A. Tevault
4.8 (5)
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The Ultimate Linux Shell Scripting Guide

The Ultimate Linux Shell Scripting Guide

4.8 (5)
By: Donald A. Tevault

Overview of this book

Embark on a comprehensive journey through command shells with this hands-on manual. While Bash is a Linux staple, Z shell and PowerShell are rising stars, applicable to Linux, macOS, and Unix. Progress seamlessly through chapters, each building on the last, creating a solid foundation. Learn through a unique approach: concepts, examples, and interactive labs. These labs, nearly a hundred strong, form the core of experiential learning, essential for script creation. Focusing on Linux commands and their scripting applications, this manual is universally relevant across Linux and select Unix-like systems. It goes beyond theory, offering practical scripts for real-world Linux administration. Scripts are designed for manageability, aiding learning and troubleshooting. The goal is to nurture the ability to craft intelligent, functional shell scripts. While centered on Bash, this book offers a peek into the future with Z Shell and PowerShell, expanding your skills and adaptability. This book is systematically structured and engaging so that it will guide you to master command shells, equipping you for real-world Linux challenges.
Table of Contents (26 chapters)
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24
Other Books You May Enjoy
25
Index

Understanding Decisions and Loops

So far, I’ve been showing you a lot of programming techniques and constructs that are specific to shell scripting. In this section, I’ll show you some constructs that are common to most all programming languages. I’ll begin by showing you another way to make decisions.

The if. .then Construct

Although the && and || decision constructs work for simple scripts, you might want to use if . . then constructs for anything more complex, such as when you would need to test for multiple conditions at once. For the first example, create the am_i_root_2.sh script, which will look like this:

#!/bin/bash
if [ $(id -u) == 0 ]; then
        echo "This user is root."
fi
if [ $(id -u) != 0 ]; then
        echo "This user is not root."
        echo "This user's name is $(id -un)."
fi

Note that each decision stanza begins with if and ends with fi. (Yes, that’s if spelled backwards...

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