Regular Expressions 101

Save & Share

  • Regex Version: ver. 8
  • Update Regex
    ctrl+⇧+s
  • Save new Regex
    ctrl+s
  • Add to Community Library

Flavor

  • PCRE2 (PHP >=7.3)
  • PCRE (PHP <7.3)
  • ECMAScript (JavaScript)
  • Python
  • Golang
  • Java 8
  • .NET 7.0 (C#)
  • Rust
  • Regex Flavor Guide

Function

  • Match
  • Substitution
  • List
  • Unit Tests

Tools

Sponsors
There are currently no sponsors. Become a sponsor today!
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

/
/
g

Test String

Code Generator

Generated Code

using System; using System.Text.RegularExpressions; public class Example { public static void Main() { string pattern = @"K'(?P<name1>81|61|64|44|86|678|41|49|33|685|1(?:33|45)?|\d{2,3})\d+"; string input = @"K'8134567 K'81345678 K'6134516789 K'61345678 K'643456 K'646345678 K'1234567890 K'12345678901 K'1454567890 <<<--- want 145 returned and not 1 K'13345678901 <<<--- want 133 returned and not 1 K'3214567890123 K'32134567890123 K'3654567890123 K'8934567890123 K'6554567890123 I am interested in the digits after K' I am looking to do this using regex but not sure if it can be done. What I want is: if the number starts with 81 return 81 if the number starts with 61 return 61 ... if the number starts with something i am not interested in return other(or its first digits of 1-3) The above criteria works: but what I also want is: if the fist digit is 1 then return 1 BUT if the fist digit is 1 and the 2nd and 3rd digit are 45 return 145 and don't return just 1 if the fist digit is 1 and the 2nd and 3rd digit are 33 return 133 and don't return just 1 I presume I have to put something inside this part of the regex |(1)\d+| Questions: Does regex sort the data first? Is the order of the regex search important to how it is implemented? i deally I do not want this. "; foreach (Match m in Regex.Matches(input, pattern)) { 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