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Regular Expressions Basics

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Questions and Answers

What is the purpose of the \b anchor in regular expressions?

To match the start of a string
To match a newline character
To match a word boundary (correct)
To match any whitespace character

What does the [a-g] pattern match in regular expressions?

Exactly one of the characters a, b, or c
Any character that is not a letter
Any character except a, b, or c
Any character between a and g (correct)

What is the purpose of a non-capturing group in regular expressions?

To match a group only at the end of a string
To match a group only at the start of a string
To capture a group for later backreference
To match a group without creating a capture (correct)

What does the \W pattern match in regular expressions?

<p>A non-word character (not alphanumeric plus underscore) (C)</p> Signup and view all the answers

What is the purpose of the a{1,3} quantifier in regular expressions?

<p>To match between one and three occurrences of a (D)</p> Signup and view all the answers

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Study Notes

Character Classes

Any character except newline: \w, \d, \s match word, digit, whitespace respectively
Not word, digit, whitespace: \W, \D, \S respectively
Match any of a, b, or c: [abc]
Not a, b, or c: [^abc]
Character between a & g: [a-g]

Anchors

Start of the string: ^
End of the string: $
Word boundary: \b
Not-word boundary: \B

Escaped Characters

Escaped special characters: \., \\
Tab, linefeed, carriage return: \t, \n, \r

Groups & Lookaround

Capture group: (abc)
Backreference to group #1: \1
Non-capturing group: (?:abc)
Positive lookahead: (?=abc)
Negative lookahead: (?!abc)

Quantifiers & Alternation

0 or more, 1 or more, 0 or 1: a*, a+, a?
Exactly five, two or more: a{5}, a{2,}
Between one & three: a{1,3}
Match as few as possible: a+?, a{2,}?
Match ab or cd: ab|cd

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