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The Ultimate Linux Shell Scripting Guide

You're reading from   The Ultimate Linux Shell Scripting Guide Automate, Optimize, and Empower tasks with Linux Shell Scripting

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Product type Paperback
Published in Oct 2024
Publisher Packt
ISBN-13 9781835463574
Length 696 pages
Edition 1st Edition
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Author (1):
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Donald A. Tevault Donald A. Tevault
Author Profile Icon Donald A. Tevault
Donald A. Tevault
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Table of Contents (26) Chapters Close

Preface 1. Getting Started with the Shell 2. Interpreting Commands FREE CHAPTER 3. Understanding Variables and Pipelines 4. Understanding Input/Output Redirection 5. Customizing the Environment 6. Text-Stream Filters – Part 1 7. Text Stream Filters – Part 2 8. Basic Shell Script Construction 9. Filtering Text with grep, sed, and Regular Expressions 10. Understanding Functions 11. Performing Mathematical Operations 12. Automating Scripts with here Documents and expect 13. Scripting with ImageMagick 14. Using awk – Part 1 15. Using awk – Part 2 16. Creating User Interfaces with yad, dialog, and xdialog 17. Using Shell Script Options with getops 18. Shell Scripting for Security Professionals 19. Shell Script Portability 20. Shell Script Security 21. Debugging Shell Scripts 22. Introduction to Z Shell Scripting 23. Using PowerShell on Linux 24. Other Books You May Enjoy
25. Index

Using here Documents

A here document is a block of code that you place into a script to perform a certain task. Yeah, I know, I said the same thing about functions. But, here documents are completely different. They’ve been around since the early days of Unix, and can be used in various different programming languages.

Formatting note: The accepted Unix and Linux convention for writing out the term “here document” is to do so in all lower-case letters. That can get a bit confusing, though. So, to eliminate the confusion, I’ll just italicize the term throughout the rest of this book, like this: here document.

Here documents work by providing another way to redirect input into a particular command. The code that performs this redirection is enclosed by a pair of limit strings, which look something like this:

command << _EOF_
. . .
Code to execute or data to display
. . .
_EOF_

The << sequence is a special type of redirector...

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