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 = /[$]([{])?([0-9]+)?(?(2)|(?:TM_FILENAME))(?(1)(?(2)[:].+|[\/].+[\/].*[\/])})/m str = 'If-Then-Else Conditionals in Regular Expressions http://www.regular-expressions.info/conditional.html $TM_FILENAME //GOOD $1 //GOOD ${1:} //BAD: empty default value ${1:a} //GOOD ${TM_FILENAME/[\\.]/_/} //GOOD ${TM_FILENAME:a|b} //BAD: cannot set default value to static var ${TM_FILENAME/} //BAD: illegal: only one `/` (need3) ${TM_FILENAME/a/} //BAD: illegal: only two `/` (need3) ${TM_FILENAME/a//} //GOOD: not empty between first two `/` ${TM_FILENAME//abc/} //BAD: this should not match: empty between first two `/` ${TM_FILENAME/a//a} //BAD: not `}` after last `/` ' # 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