Understanding Filename Expansion with Wildcards

Filename expansion, also known as file globbing, is a powerful feature in command-line shells that allows you to use wildcard characters to match multiple filenames or directory names with a single pattern. This significantly simplifies operations like listing, copying, or deleting files.

Key Concepts in Filename Expansion

• A wildcard character is a special character used to represent one or more characters in a filename or foldername.
• File globbing is the operation that recognizes these wildcard characters and performs the expansion, replacing the pattern with a list of matching files.

Common Wildcard Characters and Their Usage

Wildcard	Description	Example	Matches	Does Not Match
*	Matches 0 or more characters.	ls to*	to, tom, ton, tow, tommy, tommie	tata, tea
?	Matches exactly 1 character.	ls to?	tom, tow, ton	to, tommy, tommie, tata, tea
[abc]	Matches any single character within the brackets.	ls [bc]at	bat, cat	Bat, Cat, rat
[a-z]	Matches any single character within the specified range (case-sensitive).	ls day[1-9]	day1, day2, ..., day9	day11, day
[!abc]	Matches any single character that is NOT within the brackets.	ls [!r]at	bat, cat, Bat, Cat, Rat	rat
[!a-z]	Matches any single character that is NOT within the specified range.	ls day[!1-9]	day0, days	day1, ..., day9

Benefits of Using Filename Expansion

Leveraging filename expansion can save you a significant amount of typing and reduce the potential for errors when working with numerous files. It's a fundamental skill for efficient command-line usage.

Further Reading

• MDN Web Docs: Regular Expressions (While not identical, shares similar pattern matching concepts)
• Bash Manual: Filename Expansion