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 = /(<othermeta content="V6" name="version"\/>)(?![\s\S]*<othermeta content="V7" name="version"\/>) /m str = 'I will search for V6 If i find V6, i\'ll check for V7 AFTER V7 If V7 does not exist i will match V6 and replace it If V7 exists AFTER V6, i will NOT match V6 BUG: If V7 exists BEFORE V6, i will match V6 (i don\'t know how to create a REGEX that looks ahead and behind) Test it by changing Vy below to V7 and the match will be gone. BUG: If you change Vx to V7 it will still match V6. <othermeta content="Vx" name="version"/> <othermeta content="V5" name="version"/> <othermeta content="V6" name="version"/> <othermeta content="V6.1" name="version"/> <othermeta content="V" name="version"/>' # 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