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

`
`
gm

Test String

Code Generator

Language

Generated Code

import java.util.regex.Matcher; import java.util.regex.Pattern; public class Example { public static void main(String[] args) { final String regex = "^(?P<RuleNumber>[\\d]+)\\s+(?P<Chain>[^\\s]+):\\s+in:(?P<InputInterface>[^,]+)\\s+out:(?P<OutputInterface>[^,]+),\\s+(?:src-mac\\s+(?P<SourceMacAddress>[^,]+),\\s+)?proto\\s+(?P<Protocol>\\w+)(?:\\s+\\((?P<Flags>[^)]+)\\))?,\\s+\\[?(?P<SourceAddress>\\d{1,3}\\.\\d{1,3}\\.\\d{1,3}\\.\\d{1,3}|[a-f\\d:]+)\\]?(?::(?P<SourcePort>\\d+))?->\\[?(?P<DestinationAddress>\\d{1,3}\\.\\d{1,3}\\.\\d{1,3}\\.\\d{1,3}|[a-f\\d:]+)\\]?(?::(?P<DestinationPort>\\d+))?,\\s+len\\s+(?P<Length>\\d+)$"; final String string = "16 input: in:ether1 out:(unknown 0), src-mac 00:00:5e:00:01:f2, proto UDP, 46.72.18.53:36111->134.249.140.20:1, len 132\n" + "16 input: in:ether1 out:(unknown 0), src-mac 00:00:5e:00:01:f2, proto TCP (SYN), 201.1.133.187:19808->134.249.140.20:37215, len 44\n" + "14 forward: in:6to4-tunnel1 out:6to4-tunnel1, proto ICMP (type 128, code 0), 2001:4ca0:108:42::1:9->2a01:d0:ffff:4e:72a2:d17a:9c55:ee86, len 16\n" + "14 forward: in:6to4-tunnel1 out:6to4-tunnel1, proto ICMP (type 128, code 0), 2001:4ca0:108:42::1:9->2a01:d0:ffff:4e:72a2:d17a:9c55:ee86, len 16\n" + "14 forward: in:6to4-tunnel1 out:6to4-tunnel1, proto TCP (SYN), [2001:4ca0:108:42:0:80:6:9]:35646->[2a01:d0:ffff:4e:72a2:d17a:9c55:ee86]:80, len 40"; final Pattern pattern = Pattern.compile(regex, Pattern.MULTILINE); final Matcher matcher = pattern.matcher(string); while (matcher.find()) { System.out.println("Full match: " + matcher.group(0)); for (int i = 1; i <= matcher.groupCount(); i++) { System.out.println("Group " + i + ": " + matcher.group(i)); } } } }

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 Java, please visit: https://docs.oracle.com/javase/7/docs/api/java/util/regex/Pattern.html