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Mastering Linux Shell Scripting

You're reading from   Mastering Linux Shell Scripting Master the complexities of Bash shell scripting and unlock the power of shell for your enterprise

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Product type Paperback
Published in Dec 2015
Publisher
ISBN-13 9781784396978
Length 198 pages
Edition 1st Edition
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Author (1):
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Andrew Mallett Andrew Mallett
Author Profile Icon Andrew Mallett
Andrew Mallett
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Table of Contents (16) Chapters Close

Preface 1. What and Why of Scripting with Bash FREE CHAPTER 2. Creating Interactive Scripts 3. Conditions Attached 4. Creating Code Snippets 5. Alternative Syntax 6. Iterating with Loops 7. Creating Building Blocks with Functions 8. Introducing sed 9. Automating Apache Virtual Hosts 10. Awk Fundamentals 11. Summarizing Logs with Awk 12. A Better lastlog with Awk 13. Using Perl as a Bash Scripting Alternative 14. Using Python as a Bash Scripting Alternative Index

Simple decision paths using command-line lists


We have used command-line lists both in Chapter 1, What and Why of Scripting with Bash of this book and in some of the scripts found in Chapter 2, Creating Interactive Scripts. Lists are one of the simplest conditional statements that we can create and so we thought that it was appropriate to use them in the earlier examples before fully explaining them here.

Command-line lists are two or more statements that are joined using either the AND or OR notations:

  • &&: AND

  • ||: OR

Where the two statements are joined using the AND notation, the second command only runs if the first command succeeds. Whereas, with the OR notation the second command will run only if the first command fails.

The decision of the success or failure of a command is taken by reading the exit code from the application. A zero represents a successful application completion and anything other than a zero will represent a failure. We can test the success or failure of an...

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