Regular Expressions 101

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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

/
/
iu

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#"(?iu)^(?<localPart>(?<dotString>[0-9a-z!#$%&'*+-\/=?^_`\{|\}~\u{80}-\u{10FFFF}]+(\.[0-9a-z!#$%&'*+-\/=?^_`\{|\}~\u{80}-\u{10FFFF}]+)*)|(?<quotedString>"([\x20-\x21\x23-\x5B\x5D-\x7E\u{80}-\u{10FFFF}]|\\[\x20-\x7E])*"))(?<!.{64,})@(?<domainOrAddressLiteral>(?<addressLiteral>\[((?<IPv4>\d{1,3}(\.\d{1,3}){3})|(?<IPv6Full>IPv6:[0-9a-f]{1,4}(:[0-9a-f]{1,4}){7})|(?<IPv6Comp>IPv6:([0-9a-f]{1,4}(:[0-9a-f]{1,4}){0,5})?::([0-9a-f]{1,4}(:[0-9a-f]{1,4}){0,5})?)|(?<IPv6v4Full>IPv6:[0-9a-f]{1,4}(:[0-9a-f]{1,4}){5}:\d{1,3}(\.\d{1,3}){3})|(?<IPv6v4Comp>IPv6:([0-9a-f]{1,4}(:[0-9a-f]{1,4}){0,3})?::([0-9a-f]{1,4}(:[0-9a-f]{1,4}){0,3}:)?\d{1,3}(\.\d{1,3}){3})|(?<generalAddressLiteral>[a-z0-9-]*[[a-z0-9]:[\x21-\x5A\x5E-\x7E]+))\])|(?<Domain>(?!.{64,})(([0-9a-z\u{80}-\u{10FFFF}]([0-9a-z-\u{80}-\u{10FFFF}]*[0-9a-z\u{80}-\u{10FFFF}])?))(\.([0-9a-z\u{80}-\u{10FFFF}]([0-9a-z-\u{80}-\u{10FFFF}]*[0-9a-z\u{80}-\u{10FFFF}])?))*))$"#).unwrap(); let string = "postmaster@[123.123.32.245]"; // result will be a tuple containing the start and end indices for the first match in the string let result = regex.captures(string); let (start, end) = match result { Some((s, e)) => (s, e), None => { // ... } }; println!("{}", &string[start, end]); }

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/