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

/
/
gmix

Test String

Substitution

Processing...

Code Generator

Language

Generated Code

re = /((?:[ -$&(-[\]-~]|([%'\\])\2)*(%(\d+\$)?[-+\s0#]?(\d+|\*)?(\.\d+)?[bt]?[diuoxXfeEgGcs]+)+(?:(?!(?:[ -$&(-[\]-~]|([%'\\])\7)*(?:%(?:\d+\$)?[-+\s0#]?(?:\d+|\*)?(?:\.\d+)?[bt]?[diuoxXfeEgGcs]+)+)(?:[ -$&(-[\]-~]|([%'\\])\8)*)?) /mix str = 'Color %s, we are looking for %%02droids %% number1 %d, number2 %05d, hex %#x, float %5.2f, unsigned value %u. I wanted to also add the ability to capture "any printable text characters besides %, \' and \\, unless these characters appear exactly twice". This needs to be captured both before the initial % and after the conversion character. any printable character: [ -~] besides %, \' and \\: (?![\\\\%\']) these characters appear exactly twice: ( §§§§ |\'{2}|\\\\{2}|%{2}) (§ = placeholder) I am having a problem with the "unless", that is, getting the negative look-ahead to discard single occurrences but allow double occurrences of the specified characters. Color %s, number1 %d, number2 %05d, hex %#x, float %5.2f, unsigned value %u. | | | | | | |' subst = 'IMAGE REMOVED FROM CHROME\\r\\n' 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