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<Time>.*)\\s+(?P<DeviceIPAddress>\\d{1,3}.\\d{1,3}.\\d{1,3}.\\d{1,3})\\s+date=(?P<Date>.*)\\s+time=(?:\\d+\\W+\\d+\\W+\\d+)\\s+devname=(?<DeviceName>.*)\\s+devid=(?P<DeviceID>\\w+)\\s+logid=(?:\\d+)\\s+type=(?P<LogType>\\w+)\\s+subtype=(?P<SubType>\\w+)\\s+level=(?P<Status>\\w+)\\s+vd=(?P<User>\\w+)\\s+logdesc=[\\W+](?P<Message>.*)[\\W+]\\s+session_id=(?P<Session_ID>\\w+)\\s+policyid=(?:\\d+)\\s+srcip=(?P<SourceIP>\\d{1,3}.\\d{1,3}.\\d{1,3}.\\d{1,3})\\s+srcport=(?P<SourcePort>\\d+)\\s+dstip=(?P<DestinationIP>\\d{1,3}.\\d{1,3}.\\d{1,3}.\\d{1,3})\\s+dstport=(?P<DestinationPort>\\d+)\\s+action=(?P<Action>\\w+)\\s+alert=(?:\\d+)\\s+desc=[\\W+](?P<Description>.*)[\\W+]\\s+msg=[\\W+](?P<msg>.*)[\\W+]"; final String string = "<187>Oct 18 16:24:11 10.76.103.254 date=2020-10-18 time=16:18:44 devname=JAIPUR-FGT60D devid=FGT60D4615072349 logid=0105048038 type=event subtype=wad level=error vd=root logdesc=\"SSL Fatal Alert received\" session_id=3eb37145 policyid=0 srcip=222.186.136.150 srcport=54221 dstip=59.111.181.52 dstport=443 action=receive alert=2 desc=\"bad certificate\" msg=\"SSL Alert received\""; 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