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The Ultimate Linux Shell Scripting Guide

You're reading from   The Ultimate Linux Shell Scripting Guide Automate, Optimize, and Empower tasks with Linux Shell Scripting

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Product type Paperback
Published in Oct 2024
Publisher Packt
ISBN-13 9781835463574
Length 696 pages
Edition 1st Edition
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Author (1):
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Donald A. Tevault Donald A. Tevault
Author Profile Icon Donald A. Tevault
Donald A. Tevault
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Table of Contents (26) Chapters Close

Preface 1. Getting Started with the Shell 2. Interpreting Commands FREE CHAPTER 3. Understanding Variables and Pipelines 4. Understanding Input/Output Redirection 5. Customizing the Environment 6. Text-Stream Filters – Part 1 7. Text Stream Filters – Part 2 8. Basic Shell Script Construction 9. Filtering Text with grep, sed, and Regular Expressions 10. Understanding Functions 11. Performing Mathematical Operations 12. Automating Scripts with here Documents and expect 13. Scripting with ImageMagick 14. Using awk – Part 1 15. Using awk – Part 2 16. Creating User Interfaces with yad, dialog, and xdialog 17. Using Shell Script Options with getops 18. Shell Scripting for Security Professionals 19. Shell Script Portability 20. Shell Script Security 21. Debugging Shell Scripts 22. Introduction to Z Shell Scripting 23. Using PowerShell on Linux 24. Other Books You May Enjoy
25. Index

Hands-on Lab – Testing Conditions

For this step, download the tests-test.sh script from the Github repository. (It’s a rather long script that I can’t reproduce here, due to book formatting considerations.) Open the script in your text editor, and examine how it’s constructed. The first thing you’ll see is that it’s checking for the existence of the myfile.txt file, like this:

#!/bin/bash
[ -f myfile.txt ] && echo "This file exists." || echo "This file does not exist."

After that, you’ll see the command to create the file if it doesn’t exist, like this:

echo "We will now create myfile.txt if it does not exist, and make it with only read permissions for $USER."
[ -f myfile.txt ] || touch myfile.txt

Next, you’ll see the command to set 400 as the permissions setting, which means that the user has permission to read the file, and that nobody has permission to write to...

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