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

using System; using System.Text.RegularExpressions; public class Example { public static void Main() { string pattern = @"(\b(?:Jan(?:uary|uar)?|Feb(?:ruary|ruar)?|M(?:a|ä)?r(?:ch|z)?|Apr(?:il)?|Ma(?:y|i)?|Jun(?:e|i)?|Jul(?:y)?|Aug(?:ust)?|Sep(?:tember)?|O(?:c|k)?t(?:ober)?|Nov(?:ember)?|De(?:c|z)(?:ember)?)\b +(?:(?:0[1-9])|(?:[12][0-9])|(?:3[01])|[1-9])(?: (?>\d\d){1,2})? (?!<[0-9])(?:2[0123]|[01]?[0-9]):(?:[0-5][0-9])(?::(?:(?:[0-5]?[0-9]|60)(?:[:.,][0-9]+)?))(?![0-9])).*([A-Z0-9]+-(?:[+-]?(?:[0-9]+))-(?:[A-Z0-9_]+)).*(Built|Teardown|Deny|Denied|denied|requested|permitted|denied by ACL|discarded|est-allowed|Dropping|created|deleted).*((?<![0-9])(?:(?:[0-1]?[0-9]{1,2}|2[0-4][0-9]|25[0-5])[.](?:[0-1]?[0-9]{1,2}|2[0-4][0-9]|25[0-5])[.](?:[0-1]?[0-9]{1,2}|2[0-4][0-9]|25[0-5])[.](?:[0-1]?[0-9]{1,2}|2[0-4][0-9]|25[0-5]))(?![0-9]))((?:\/[A-Za-z0-9$.+!*'(){},~:;=@#%_\-]*)+(?:\?[A-Za-z0-9$.+!*'|(){},~@#%&\/=:;_?\-\[\]<>]*)?)"; string input = @"Mar 29 2004 09:54:18: %PIX-6-302005: Built UDP connection for faddr 198.207.223.240/53337 gaddr 10.0.0.187/53 laddr 192.168.0.2/53"; RegexOptions options = RegexOptions.Multiline; foreach (Match m in Regex.Matches(input, pattern, options)) { Console.WriteLine("'{0}' found at index {1}.", m.Value, m.Index); } } }

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 C#, please visit: https://msdn.microsoft.com/en-us/library/system.text.regularexpressions.regex(v=vs.110).aspx