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"
"
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<remote>(?:[0-9]{1,3}\\.){3}[0-9]{1,3})\\s+(?P<refid>(?:(?:[0-9]{1,3}\\.){3}[0-9]{1,3})|(.LOCL.|.INIT.))\\s+(?P<st>\\d+)\\s+(?P<t>\\w)\\s+(?P<when>\\d+|-)\\s+(?P<poll>\\d+)\\s+(?P<reach>\\d+)\\s+(?P<delay>-?(?:\\d+).?\\d+)\\s+(?P<offset>-?(?:\\d+).?\\d+)\\s+(?P<jitter>-?(?:\\d+).?\\d+)"; final String string = "+172.18.251.100 129.6.15.29 2 u 715 1024 377 0.135 1.820 2.397\n" + "-172.28.251.100 132.163.97.6 2 u 898 1024 377 0.193 -1.765 1.040\n" + "+172.18.251.101 129.6.15.30 2 u 673 1024 377 0.076 -0.358 0.452\n" + "*172.28.251.101 129.6.15.30 2 u 172 1024 377 0.075 0.690 0.165\n" + " 127.127.1.0 .LOCL. 10 l 1251 64 0 0.000 0.000 0.000\n" + " 172.30.251.100 .INIT. 16 u - 1024 0 0.000 0.000 0.000\n" + " 172.30.251.101 .INIT. 16 u - 1024 0 0.000 0.000 0.000"; 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