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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
Tools
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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

Returning values from functions


Whenever we have statements that are printed on the screen within the function, we can see their result. However, many times we will want the function to populate a variable within the script and not display anything. In this case, we use return in the function. This is especially important when we are gaining input from users. We may prefer the case to translate the input to a known case to make the condition testing easier. Embedding the code in a function allows it to be used many times within a script. The following code shows how we can achieve this by creating the to_lower function:

function to_lower ()
{
    input="$1"
    output=$(tr [A-Z] [a-z] <<<"$input")
return $output
}

Stepping through the code we can begin to understand the operation of this function:

  • input="$1": This is more for ease than anything else; we assign the first input parameter to a named variable input.

  • output=$(tr [A-Z] [a-z] <<< "$input"): This is the main engine...

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