Regular Expressions 101

Group 1(<link\s+[^>]*rel\s*=\s*(['"])stylesheet\2.*?>)

<linkthe literal text <link (case insensitive)

\s+any whitespace character, repeated at least once

Negated Character Class[^>]*

*matches any number of characters outside the set below:

>the literal > (62₁₀ / 76₈ / 3E₁₆)

relthe literal text rel (case insensitive)

\s*any whitespace character, repeated any number of times

=the literal = (61₁₀ / 75₈ / 3D₁₆)

\s*any whitespace character, repeated any number of times

Group 2(['"])

Character Class['"]

'the literal ' (39₁₀ / 47₈ / 27₁₆)

"the literal " (34₁₀ / 42₈ / 22₁₆)

stylesheetthe literal text stylesheet (case insensitive)

\2the text saved by group 2

.*?any character, repeated any number of times

>the literal > (62₁₀ / 76₈ / 3E₁₆)

Non-Capturing Group(?:(?=.*<\/head))

Positive Lookahead(?=.*<\/head)

.*any character, repeated any number of times

<the literal < (60₁₀ / 74₈ / 3C₁₆)

\/the literal / (47₁₀ / 57₈ / 2F₁₆)

headthe literal text head (case insensitive)

Global pattern flags

g modifier: global. Finds all matches instead of stopping after the first

m modifier: multiline. Causes ^ and $ to match the start and end of each line, not only the start and end of the string

s modifier: single line. Allows a dot to match line terminators

i modifier: insensitive. Matches without distinguishing uppercase and lowercase letters

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25 tokens

Regular Expression

(<link\s+[^>]*rel\s*=\s*(['"])stylesheet\2.*?>)(?:(?=.*<\/head))

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