Regular Expressions 101

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An explanation of your regex will be automatically generated as you type.
Detailed match information will be displayed here automatically.
  • All Tokens
  • Common Tokens
  • General Tokens
  • Anchors
  • Meta Sequences
  • Quantifiers
  • Group Constructs
  • Character Classes
  • Flags/Modifiers
  • Substitution
  • A single character of: a, b or c
    [abc]
  • A character except: a, b or c
    [^abc]
  • A character in the range: a-z
    [a-z]
  • A character not in the range: a-z
    [^a-z]
  • A character in the range: a-z or A-Z
    [a-zA-Z]
  • Any single character
    .
  • Alternate - match either a or b
    a|b
  • Any whitespace character
    \s
  • Any non-whitespace character
    \S
  • Any digit
    \d
  • Any non-digit
    \D
  • Any word character
    \w
  • Any non-word character
    \W
  • Non-capturing group
    (?:...)
  • Capturing group
    (...)
  • Zero or one of a
    a?
  • Zero or more of a
    a*
  • One or more of a
    a+
  • Exactly 3 of a
    a{3}
  • 3 or more of a
    a{3,}
  • Between 3 and 6 of a
    a{3,6}
  • Start of string
    ^
  • End of string
    $
  • A word boundary
    \b
  • Non-word boundary
    \B

Regular Expression
No Match

/
/
gm

Test String

Code Generator

Language

Generated Code

re = /(<(span).+?><(strong|em)>(.+?)<\/\3><\/\2>)/m str = '<p>Alligators much like birds, have been shown to exhibit unidirectional movement of air through their lungs. Most other amniotes are believed to exhibit bidirectional, or tidal breathing. For <span style="color: #3a9ee3;"><strong>alligator</strong></span> tidal breathing <span style="color: #3a9ee3;"><strong>alligator</strong></span> animal, such as a mammal, air flows into and out of the <span style="color: #169179;"><em>alligators</em></span> lungs through alligator branching bronchi which terminate in small <em>alligator</em> dead-end chambers called alveoli. As the alveoli represent <span style="color: #3a9ee3;"><strong>Lion</strong></span> dead-ends to flow, the inspired air must move back out the same way it came in. In contrast, air in <span style="color: #3a9ee3;"><strong>alligator</strong></span> lungs makes a circuit, moving in only one direction through the parabronchi. The <span style="color: #3a9ee3;"><strong>alligators</strong></span> lungs are no joke! The air first enters the outer branch, moves through the parabronchi, and exits <span style="color: #3a9ee3;"><strong>alligators</strong></span> the lung through the inner branch. Oxygen alligator exchange takes place <span style="color: #3a9ee3;"><strong>Alligators</strong></span> in extensive vasculature around the alligator.</p>' # Print the match result str.scan(re) do |match| puts match.to_s end

Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for Ruby, please visit: http://ruby-doc.org/core-2.2.0/Regexp.html