Shell scripts are everywhere, especially those written in bash compatible syntax, and it's extremely useful to be able to understand and write them, but they can be complex and obscure. Complexity is the enemy of security, but it's also the enemy of readability and understanding. With this practical book, you'll learn how to decipher old bash code and write new code that's as clear and readable as possible. Your future you will thank you.
Authors Carl Albing and JP Vossen show you how to use the power and flexibility of the shell to your advantage. You'll learn how to read and write scripts like an expert, so that you can:
• Write useful, flexible, and readable bash code...with style
• Decode bash code such as ${MAKEMELC,,} and ${PATHNAME##*/}
• Save time and ensure consistency when automating tasks
• Amaze and impress colleagues with bash idioms
• Discover how bash idioms can make your code clean and concise
Author(s): Carl Albing, JP Vossen
Edition: 1
Publisher: O'Reilly Media
Year: 2022
Language: English
Commentary: Vector PDF
Pages: 170
City: Sebastopol, CA
Tags: Linux; Unix; Programming; Best Practices; Shell Scripting; bash
Cover
Copyright
Table of Contents
Preface
Running bash
bash on Mac
bash in Containers
Revision Control
Hello World
Conventions Used in This Book
Using Code Examples
O’Reilly Online Learning
How to Contact Us
Acknowledgments
bash
Reviewers
O’Reilly
From Carl
From JP
Chapter 1. A Big “if” Idiom
The Big “if”
Or ELSE…
More than One
More than One Again
Don’t Do This
Style and Readability: Recap
Chapter 2. Looping Lingo
Looping Constructs
Explicit Values
Similar to Python
Quotes and Spaces
Developing and Testing for Loops
while and until
Style and Readability: Recap
Chapter 3. Just in CASE
Make Your Case
A Realistic Use Case
Motivation
Our Script
Wrapper Scripts
One More Twist
Style and Readability: Recap
Chapter 4. Variable Vernacular
Variable Reference
Parameter Expansion
Shorthand for basename
Path or Prefix Removal
Shorthand for dirname or Suffix Removal
Other Modifiers
Conditional Substitutions
Default Values
Comma-Separated Lists
Modified Value
$RANDOM
Command Substitution
Style and Readability: Recap
Chapter 5. Expressions and Arithmetic
Arithmetic
No Parentheses Needed
Compound Commands
Style and Readability: Recap
Chapter 6. Functional Framework
Calling Functions
Defining Functions
Function Parameters
Function Return Values
Local Variables
Function Special Cases
Time for printf
POSIX Output
Getting or Using the Date and Time
printf for Reuse or Debugging
Style and Readability: Recap
Chapter 7. List and Hash Handling
Commonalities
Lists
Hashes
A Simple Word Count Example
Style and Readability: Recap
Chapter 8. Arguing
Your First Argument
Having Options
Parsing Options
Long Arguments
HELP!
Debug and Verbose
Version
Style and Readability: Recap
Chapter 9. Files and More
Reading Files
read
mapfile
Brute Force
Fiddling with $IFS for Fun and Profit, to Read Files
Pretend Files
Drop-in Directories
Using a Library
Shebang!
Unofficial bash Strict Mode
Exit Codes
It’s a Trap!
Here-Documents and Here-Strings
Are We Interactive?
Summary
Chapter 10. Beyond Idioms: Working with bash
Prompts
bash Time Zone
Getting User Input
read
pause
select
Aliases
Functions
Local Variables
Readline Hacks
Using logger from bash
Handling JSON with jq
Grepping the Process List
Rotating Old Files
Embedded Documentation
bash Debugging
bash Unit Testing
Summary
Chapter 11. Developing Your Style Guide
Readability
Comments
Names
Functions
Quoting
Layout
Syntax
Other
Script Template
Other Style Guides
bash Linter
Summary
Appendix A. The bash Idioms Style Guide
Readability
Comments
Names
Functions
Quoting
Layout
Syntax
Other
Script Template
Index
About the Authors
Colophon
