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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

Introducing functions


Functions are blocks of code that exist in memory as named elements. These elements can be created within the shell environment, as well as within the script execution. When a command is issued at the command line, aliases are checked first and following this we check for a matching function name. To display the functions residing in your shell environment, you can use the following code:

$ declare -F

The output will vary depending on the distribution you are using and the number of functions you have created. On my Raspbian OS, the partial output is shown in the flowing screenshot:

Using the -f option, you can display the function and the associated definition. However, if we want to see just a single function definition, we can use the type command:

$ type quote

The previous code example will display the code block for the quote function, if it exists within your shell. We can see the output of this command in the following screenshot:

The quote function in bash inserts...

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