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 = /[A-Z]\S*\.[^\S\r\n]+[A-Z]|(?:^|[.!?][\t ]+)([A-Z]\S*)/m str = 'We went to Dr. Smith\'s office This is a proper sentence. It is followed by another sentence. What happens when an abbreviation like NASA enters the scene? What about N.A.S.A with the dots in between? It is NASA! No one will convince me otherwise! N.A.S.A. at the start of a sentence? N.A.S.A. immediately after? At the end of the sentence: NASA. But also with the dots: N.A.S.A. Filler sentence here. The compromise of catching situations like Dr. Smith is that words at the end of a sentence cannot start with a capital letter. While This Regex Doesn\'t Match Every Word As The Start Of A Sentence Here, It Won\'t Detect The Start Of The Next Sentence. Case in point. Abbreviations like LIKE currently pose a problem. The second regex has false negatives: it will fail to match `So` in `This is sentence is English. So is this one.` ' # 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