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Learn Linux Shell Scripting – Fundamentals of Bash 4.4

You're reading from   Learn Linux Shell Scripting ‚àö¬¢‚Äö√ᬮ‚Äö√Ñ√∫ 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

Loop control


At this point, you should feel comfortable with using while and for loops. There is one more, rather important, topic to discuss with regards to loops: loop control. Loop control is a generic term, for anything that you do to, well, control the loop! However, there are two keywords that we'll need if we want to unleash the full power of loops: break and continue. We'll start with break.

Breaking the loop

For some scripting logic, it will prove necessary to break out of the loop. You might imagine that, in one of your scripts, you are waiting for something to finish. As soon as that happens, you want to do something. Waiting and periodically checking inside a while true loop could be an option for this, but if you recall in the while-interactive.sh script, we exited on the successful answer to the riddle. On an exit, we cannot run any more commands that are outside of the while loop! This is where break comes into play. It allows us to exit the loop, but continue the script. First...

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