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

Substitution

Processing...

Code Generator

Language

Generated Code

#include <MsgBoxConstants.au3> ; to declare the Constants of MsgBox Local $sRegex = "(?m)(\b(?'first_word'[A-Z](?!([A-Z0-9]*\b|[[:alnum:]]*_)(?# the word isn't in all caps and doesn't contain underscores))(?:[a-z0-9]*)))|(\G(?'trailing_word'[A-Z][a-z0-9]*))" Local $sString = "PascalCase" & @CRLF & _ "Pascal " & @CRLF & _ "PascalCaseCase" & @CRLF & _ "Pascal684Case" & @CRLF & _ "Pas45calCase" & @CRLF & _ "PascalCase6523Case" & @CRLF & _ "PascalCaseCaseCase" & @CRLF & _ "PPascal" & @CRLF & _ "PascalCCase" & @CRLF & _ "camelCase" & @CRLF & _ "// some random commentary with Capitalized and SCREAMING letters" & @CRLF & _ "SCREAMING_SNAKE_CASE" & @CRLF & _ "Pascal_Snake_Case" & @CRLF & _ "" Local $sSubst = "\L${first_word}${trailing_word:+_\L${trailing_word}:}" Local $sResult = StringRegExpReplace($sString, $sRegex, $sSubst) MsgBox($MB_SYSTEMMODAL, "Result", $sResult)

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 AutoIt, please visit: https://www.autoitscript.com/autoit3/docs/functions/StringRegExp.htm