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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
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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

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 command:

$ declare -F  

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

Using the small -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...

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