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
  • Match everything enclosed
    (?:...)
  • Capture everything enclosed
    (...)
  • 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

// include the latest version of the regex crate in your Cargo.toml extern crate regex; use regex::Regex; fn main() { let regex = Regex::new(r"(?m)\S+\d\.\d+").unwrap(); let string = "Internet Uplink FON 41.79.9.117 : Successful Microtik 194.201.253.246 : Successful Rooftop Switch 213.150.96.166: Successful TELNET TEST telnet mail.kenyaweb.com 25 : Connected to mail.kenyaweb.com. Escape character is '^]'. 220 mail.kenyaweb.com ESMTP Postfix telnet mail.kenyaweb.com 110: Connected to mail.kenyaweb.com. Escape character is '^]'. +OK POP3 ready MAIL SERVERS mail.kenyaweb.com 194.201.253.165 : Successful Relay.kenyaweb.com 194.201.253.124 : Successful pop.kenyaweb.com 194.201.253.11 : Successful hosting.kenyaweb.com 194.201.253.132 : Successful WEB SERVERS Web server 1 194.201.253.70 : Successful Web server 2 194.201.253.8 : Successful Web Server 3 194.201.253.5 : Successful sungura.kenyaweb.com 192.64.112.132: Successful DNS Linux.form-net.com 194.201.253.105 : Successful ns200.kenyaweb.com 194.201.253.186 : Successful ns201.kenyaweb.com 194.201.253.189 : Successful ns203.kenyaweb.com 63.250.47.221 : Successful BROWSE TEST www.kenyaweb.com http://www.kenyaweb.com : Successful www.yahoo.com http://www.yahoo.com : Successful www.google.com http://www.google.com : Successful MAIL TEST Mail.Kenyaweb to yahoo : Received Mail.Kenyaweb to gmail : Received Yahoo to Mail.Kenyaweb : Received Gmail to Mail.Kenyaweb : Received"; // result will be an iterator over tuples containing the start and end indices for each match in the string let result = regex.captures_iter(string); for mat in result { println!("{:?}", mat); } }

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 Rust, please visit: https://docs.rs/regex/latest/regex/