Common patterns and character classes in Ruby - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the character class [a-z] represent in Ruby regular expressions?

It matches any single lowercase letter from a to z.

beginner

What does the pattern \d match in Ruby regular expressions?

It matches any single digit character, equivalent to [0-9].

intermediate

Explain the difference between \w and \W in Ruby regex.

\w matches any word character (letters, digits, and underscore), while \W matches any character that is NOT a word character.

beginner

What does the pattern \s match in Ruby regular expressions?

It matches any whitespace character, including spaces, tabs, and newline characters.

beginner

How do you match any character except a newline in Ruby regex?

Use the dot . character, which matches any character except newline by default.

Which pattern matches any uppercase letter in Ruby regex?

A \d

B [A-Z]

C [a-z]

D \s

The pattern [A-Z] matches any uppercase letter from A to Z.

What does the pattern \D match?

A Any non-digit

B Any digit

C Any whitespace

D Any word character

\D matches any character that is NOT a digit.

Which pattern matches a whitespace character?

A \d

B \w

C \s

D \W

\s matches any whitespace character like space, tab, or newline.

What does the pattern [^a-z] mean?

A Matches any lowercase letter

B Matches whitespace only

C Matches digits only

D Matches any character except lowercase letters

The caret ^ inside brackets negates the class, so it matches any character except lowercase letters.

Which pattern matches any word character?

A \w

B \D

C \s

D \W

\w matches letters, digits, and underscore characters.

Describe the common character classes used in Ruby regular expressions and give an example of each.

Think about digits, letters, and spaces.

Explain how to use negation inside character classes in Ruby regex and provide an example pattern.

Negation flips what the class matches.