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

r"
"

Test String

Code Generator

Language

Generated Code

use strict; my $str = ' Interface IP-Address OK? Method Status Protocol TenGigabitEthernet1/1 unassigned YES NVRAM up up Te1/1.200 216.254.132.249 YES NVRAM up up Te1/1.201 10.201.120.173 YES NVRAM up up TenGigabitEthernet1/2 10.201.121.46 YES NVRAM up up TenGigabitEthernet1/3 unassigned YES NVRAM up up Te1/3.905 198.32.160.89 YES NVRAM up up Te1/3.908 206.130.10.3 YES NVRAM up up TenGigabitEthernet1/4 unassigned YES NVRAM administratively down down TenGigabitEthernet1/5 unassigned YES NVRAM up up Te1/5.98 216.254.131.1 YES NVRAM up up Te1/5.100 216.254.130.129 YES NVRAM administratively down down Te1/5.106 216.254.130.158 YES NVRAM administratively down down Te1/5.110 216.254.131.149 YES NVRAM up up Te1/5.111 216.254.131.117 YES NVRAM up up Te1/5.132 216.254.130.25 YES NVRAM administratively down down Te1/5.134 216.254.130.29 YES NVRAM up up Te1/5.205 216.254.141.153 YES NVRAM up up TenGigabitEthernet1/6 unassigned YES NVRAM up down TenGigabitEthernet1/7 unassigned YES NVRAM up up Te1/7.907 198.32.118.14 YES NVRAM up up TenGigabitEthernet1/8 10.201.121.154 YES NVRAM up up GigabitEthernet2/1 unassigned YES unset up up GigabitEthernet2/2 unassigned YES unset administratively down down GigabitEthernet2/3 unassigned YES unset administratively down down GigabitEthernet2/4 unassigned YES unset up up GigabitEthernet2/5 unassigned YES unset administratively down down '; my $regex = qr/[0-9]*\.[0-9]+\.[0-9]+\.[0-9]/p; if ( $str =~ /$regex/ ) { 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