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Mastering Linux Shell Scripting

You're reading from   Mastering Linux Shell Scripting A practical guide to Linux command-line, Bash scripting, and Shell programming

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Product type Paperback
Published in Apr 2018
Publisher
ISBN-13 9781788990554
Length 284 pages
Edition 2nd Edition
Languages
Tools
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Authors (2):
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Mokhtar Ebrahim Mokhtar Ebrahim
Author Profile Icon Mokhtar Ebrahim
Mokhtar Ebrahim
Andrew Mallett Andrew Mallett
Author Profile Icon Andrew Mallett
Andrew Mallett
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Toc

Table of Contents (17) Chapters Close

Preface 1. The 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 the Stream Editor 9. Automating Apache Virtual Hosts 10. AWK Fundamentals 11. Regular Expressions 12. Summarizing Logs with AWK 13. A Better lastlog with AWK 14. Using Python as a Bash Scripting Alternative 15. Assessments 16. Other Books You May Enjoy

Passing options

So far, we have seen in the first chapter how to read parameters from the user. Also, you can pass options. So, what are options? And how are they different from parameters?

Options are characters with a single dash before them.

Check out this example:

$ ./script1.sh -a

The -a is an option. You can check from your script if the user entered this option; if so, then your script can behave in some manner.

You can pass multiple options:

$ ./script1.sh -a -b -c

To print these options, you can use the $1, $2, and $3 variables:

#!/bin/bash
echo $1
echo $2
echo $3

We should check these options, but, since we haven't discussed conditional statements yet, we will keep it simple for now.

Options can be passed with a value, like this:

$ ./script1.sh -a -b 20 -c

Here the -b option is passed with a value of 20.

As you can see, the variable $3=20, which is the passed...

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