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

r'
'
gm

Test String

Substitution

Processing...

Code Generator

Language

Generated Code

re = /(?<=\s)((?:docstring|some_detailed_notes)\s*=\s*\(?\s*(?:\/\/.*\n\s*)*)"((?:[^"\\]|\\.)+)"(\s*\)?\s*;)/m str = 'class myClassA(myBaseClass) { docstring = // End-of-line-comments possible " This is my class description docstring stored in a string variable inherited from myBaseClass. The content of this string, INCLUDING INDENTATION, MUST NOT be changed. "; docstring = ( " Enclosed in parentheses " ); // This variable is declared as string has a mismatched indentation: string some_detailed_notes = "Some string like this is also possible. Also with some really strange indentation and `inline code`, ```code blocks``` $\\\\text{LaTeX}$ $$\\\\frac{1}{2}$$ :::{hint} some admonitions ::: and all kind of special characters such as: \\" (...) {...} [...] ;., etc. which MUST be preserved."; string some_other_string = " do NOT touch this, only docstring and some_detailed_notes "; }' subst = '\\1R""""\\2""""\\3' result = str.gsub(re, subst) # Print the result of the substitution puts result

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