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

/
/
gmx

Test String

Code Generator

Language

Generated Code

using System; using System.Text.RegularExpressions; public class Example { public static void Main() { string pattern = @"^#start of line (?![^\n!]*!{2,}) (?=[^_\n]*_[^_]*) #if _ exists, then: ([^_:]+) #mandatory group 1 ((?=:[^:\n]):[^:_(\n]+|) #optional group 2 (_(?!_)) #group 3 mandatory ([^_\-(\n]+) # group 4 mandatory \( #mandatory ( ([^()\n]+) # group 5 mandatory \) #mandatory ) ((?=!)!|) # group 6 optional ((?=:[^!:@\n]):[^!:@\n]+|) # group 7 optional ((?=::[^!:@\n])::[^!:@\n]+|) #group 8 optional ((?=@[^!:@\n])@[^!:@\n]+|) #group 9 optional $ #end of line"; string input = @"# OK - Matches all components if all are provided contextClassName:pc_ruleName(param_One paramTwo)!:pc::pe@media # OK - Return group 2 blank when no : exists before _ which is group 3 contextClassName_ruleName(param_One paramTwo)!:pc::pe@media # OK - When ! is not provided return group 6 blank contextClassName_ruleName(param_One paramTwo):pc::pe@media # NOTOK - More than one consecutive ! contextClassName_ruleName(param_One paramTwo)!!:pc::pe@media # NOTOK - 3 More than two : at instruction tail contextClassName_ruleName(param_One paramTwo):::pe@media # OK - 2 At instruction tail :: is resolved to group 8 contextClassName_ruleName(param_One paramTwo)::pe@media # OK - 1 At instruction tail : is resolved to group 7 contextClassName_ruleName(param_One paramTwo):pe@media # OK - At instruction start : followed by chars contextClassName:pc_ruleName(param_One paramTwo):pe@media # NOTOK - At instruction start : not followed by chars contextClassName:_ruleName(param_One paramTwo):pe@media # NOTOK - At instruction start :: followed by chars contextClassName::pc_ruleName(param_One paramTwo):pe@media # OK - Whole instruction tail is optional contextClassName:pc_ruleName(param_One paramTwo) # OK - Parameter value can contain anything contextClassName:pc_ruleName(param_One param#$^Two)"; RegexOptions options = RegexOptions.Multiline | RegexOptions.IgnorePatternWhitespace; 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