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Learn Linux Shell Scripting – Fundamentals of Bash 4.4

You're reading from   Learn Linux Shell Scripting – Fundamentals of Bash 4.4 A comprehensive guide to automating administrative tasks with the Bash shell

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Product type Paperback
Published in Dec 2018
Publisher Packt
ISBN-13 9781788995597
Length 452 pages
Edition 1st Edition
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Author (1):
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Sebastiaan Tammer Sebastiaan Tammer
Author Profile Icon Sebastiaan Tammer
Sebastiaan Tammer
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Table of Contents (20) Chapters Close

Preface 1. Introduction 2. Setting Up Your Local Environment FREE CHAPTER 3. Choosing the Right Tools 4. The Linux Filesystem 5. Understanding the Linux Permissions Scheme 6. File Manipulation 7. Hello World! 8. Variables and User Input 9. Error Checking and Handling 10. Regular Expressions 11. Conditional Testing and Scripting Loops 12. Using Pipes and Redirection in Scripts 13. Functions 14. Scheduling and Logging 15. Parsing Bash Script Arguments with getopts 16. Bash Parameter Substitution and Expansion 17. Tips and Tricks with Cheat Sheet 18. Assessments 19. Other Books You May Enjoy

Positional parameters versus flags

We'll start this chapter off with a short recap on positional arguments. As you might remember from Chapter 8, Variables and User Input, we are able to use positional parameters to pass arguments to our scripts.

To put this simply, the following syntax is used:

bash script.sh argument1 argument2 ...

Inside the preceding (fictive) script.sh, we can then grab the values supplied by the user by looking at the positions the arguments are supplied in: $1 is the first argument, $2 is the second, and so on. Remember that $0 is a special argument, which relates to the name of the script: in this case, script.sh.

This approach is relatively simple, but also susceptible to errors. When you write this script, you need to check extensively for the input supplied by the user; did they give enough arguments, but not too many? Or, perhaps some arguments...

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