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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

Script comments


We should always introduce commenting scripts early in the piece. A script comment is prefaced with a # symbol. Anything after the # symbol is a comment and is not evaluated by the script. The shebang, #!/bin/bash, is primarily a comment and, as such, is not evaluated by the script. The shell running the script reads the shebang so it knows which command interpreter to hand the script over to. A comment may be at the start of a line or partly into the line. Shell scripting does not have the notion of multi-line comments.

If you are not already familiar with comments, then they are added to the script to tell all about who wrote the script, when it was written and last updated, and what the script does. It is the metadata of the script.

The following is an example of comments in scripts:

#!/bin/bash
# Welcome script to display a message to users on login
# Author: @theurbanpenguin
# Date: 1/1/1971

It is a good practice to comment and add comments that explain what the code is...

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