Regular Expressions 101

Save & Share

  • Regex Version: ver. 1
  • Update Regex
    ctrl+⇧+s
  • Save new Regex
    ctrl+s
  • Add to Community Library

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

// 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)[sS]ee, e\.g\.,.*?(?:\(D\.C\. Cir\..*(?:(\(11th Cir\.)|((\(10th Cir\.)|((\(9th Cir\.)|((\(8th Cir\.)|((\(7th Cir\.)|((\(6th Cir\.)|((\(5th Cir\.)|((\(4th Cir\.)|((\(3d Cir\.)|((\(2d Cir\.)|(\(1st Cir\.)))))))))))|(?1).*(?2)|(?3).*(?4)|(?5).*(?6)|(?7).*(?8)|(?9).*(?10)|(?11).*(?12)|(?13).*(?14)|(?15).*(?16)|(?17).*(?18)|(?19).*(?20)).*\.").unwrap(); let string = "See, e.g., Smith v. U.S. (1st Cir. 2012); U.S. v. Sara (5th Cir. 2017). See, e.g., Jefferson v. U.S. (10th Cir. 2012); U.S. v. Coolidge (D.C. Cir. 2017). See, e.g., Lincoln v. Jones (3d Cir. 2012); U.S. v. Roosevelt (9th Cir. 2017). See, e.g., Smith v. U.S. (5th Cir. 2012); U.S. v. Sara (1st Cir. 2017). See, e.g., Jefferson v. U.S. (D.C. Cir. 2012); U.S. v. Coolidge (10th Cir. 2017). See, e.g., Lincoln v. Jones (9th Cir. 2012); U.S. v. Roosevelt (3d Cir. 2017)."; // 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/