Regular Expressions 101

Save & Share

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
No Match

/
/
gsU

Test String

Code Generator

Language

Generated Code

use strict; my $str = ' <?xml version="1.0"?> <Name attribute = "value" attribute2="value2" >Convert number to string</Name> <CommandLine>Examp1.EXE</CommandLine> <Input>1</Input> <Output>One</Output> <Test TestId="0002" TestType="CMD"> <Name>Find succeeding characters</Name> <CommandLine>Examp2.EXE</CommandLine> <Input>abc</Input> <Output>def</Output> </Test> <Test TestId="0003" TestType="GUI"> <Name>Convert multiple numbers to strings</Name> <CommandLine>Examp2.EXE /Verbose</CommandLine> <Input>123</Input> <Output>One Two Three</Output> </Test> <Test TestId="0004" TestType="GUI"> <Name>Find correlated key</Name> <CommandLine>Examp3.EXE</CommandLine> <Input>a1</Input> <Output>b1</Output> </Test> <Test TestId="0005" TestType="GUI"> <Name>Count characters</Name> <CommandLine>FinalExamp.EXE</CommandLine> <Input>This is a test</Input> <Output>14</Output> </Test> <Test TestId="0006" TestType="GUI"> <Name>Another Test</Name> <CommandLine>Examp2.EXE</CommandLine> <Input>Test Input</Input> <Output>10</Output> </Test> <Test/> <Test /> <Test></Test> <Test attribute = "value" attribute2="value2"/> <Test attribute = "value" attribute2="value2" /> <Test attribute = "value" attribute2="value2" ></Test> <([^\\/> ]+?)\\s*?([^>]*)\\s*(?:\\/>|>(.*)<\\/\\1>) - (with g-, s- & U-modifiers) finds all tags in scope 1st group is tagname 2nd group is attributes 3rd group (if it exists) is value of the tag Apply pattern again on 3th group to find internal tags (recurse in the code to parse entire xml!) Apply pattern below on 2nd group to find all attributes: \\s*([^<>\\=" ]+)\\s*=\\s*"([^"]*)" - (with g-modifier) finds attributes 1st group is attributename 2nd group is attributevalue'; my $regex = qr/<([^\/> ]+?)\s*?([^>]*)\s*(?:\/>|>(.*)<\/\1>)/sp; if ( $str =~ /$regex/g ) { print "Whole match is ${^MATCH} and its start/end positions can be obtained via \$-[0] and \$+[0]\n"; # print "Capture Group 1 is $1 and its start/end positions can be obtained via \$-[1] and \$+[1]\n"; # print "Capture Group 2 is $2 ... and so on\n"; } # ${^POSTMATCH} and ${^PREMATCH} are also available with the use of '/p' # Named capture groups can be called via $+{name}

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 Perl, please visit: http://perldoc.perl.org/perlre.html