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

/
/
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)^\b(0|[1-9][0-9]{0,3}|[1-5][0-9]{4}|6[0-4][0-9]{3}|65[0-4][0-9]{2}|655[0-2][0-9]|6553[0-5])\b\h(\.|\b((?=.{1,255}$)(?:xn\-\-)?(?!-)(?!.*--)[a-z0-9]([a-z0-9-]{0,61}[a-z0-9])?(?:\.[a-z0-9]([a-z0-9-]{0,61}[a-z0-9])?)*\.?)\b)(?:\.)?(?!=)(\h(([a-z0-9-]{1,63})((\=\")[\x21\x23-\x27\x2A-\x3A\x3C-\x7E]{1,255}+(\"))?)?)*?$"#).unwrap(); let string = "230 example.com 56 subsubdomain.subdomain.example.com.thisisaverylongdomainnamewithseventycharacters 89 subsubdomain.subdomain.example.com.thisisaverylongdomainnamewithseventycharacters test 1 gOOglE.com alpn=\"h3,h2\" 250 exmpla.com test=\"test\" 250 exmpla.com 33=\"3.63\" 250 . 33=\"363\" 1 . alpn=\"h3,h2\" 1 example.com. alpn=\"h3,h2\" 2 . test=test 3 . test=\"\" 1 . alpn=\"h3,h2\" ipv4hint=\"192.0.2.1\" ipv6hint=\"2001:db8::1\" 1 . alpn=\"h3,h2\" ipv4hi-nt=\"192.0.2.1\" ipv6hint=\"2001:db8::1\" 1 test.org alpn=\"h3,h2\" ipv4hi-nt=\"192.0.2.1\" ipv6hint=\"2001:db8::1\" 1 test.org alpn=\"h3,h2\" ipv4hi-nt=\"192.0.2.1\" ipv6hint=\"2001:db8::1\" ipv4hi-nt=\"192.0.2.1\" ipv6hint=\"2001:db8::1\" ipv4hi-nt=\"192.0.2.1\" ipv6hint=\"2001:db8::1\" ipv4hi-nt=\"192.0.2.1\" ipv6hint=\"2001:db8::1\" ipv4hi-nt=\"192.0.2.1\" ipv6hint=\"2001:db8::1\" 1 test.org alpnfeefefefefefwefwefwefwefwefwefwefwefwefwefwefwefhththegerg=\"h3,h2\" 1 test.org alpnfeefefefefefwefweefwefwefwefwefwefwefwefwefhththegerg=\"h3\\,h2\" 1 test.org test=\"jn7j64m764mi67i4i467nhin0iu4n6nizn4i0n6z34htj0nizn4i0n6z34htj03ht834t03h480th3hunizn4i0n6z34htj03ht834t03h480th3hunizn4i0n6z34htj03ht8303ht834t03h480th3hunizn4i0n4t03h480th3hunizn4i0n6z34htj03ht834t03h480th3hu3ht834t03h480th3hu93hu4nu9o83h\" 1 test.org test=\"jn7j64m764mi67i4i467nhin0iu4n6nizn4i0n6z34htj0nizn4i0n6z34htj03ht834t03h480th3hunizn4i0n6z34htj03ht834t03h480th3hunizn4i0n6z34htj03ht803ht834t03h480th3hunizn4i0n4t03h480th3hunizn4i0n6z34htj03ht834t03h480th3hu3ht834t03h480th3hu93hu4nu9hho83h\" 1 test.org a=\"h3,h2\" alpn=\"h3,h2\" 3 . test 3 . test test test 1 . 1 überall-ist.de 1 xn--berall-ist-8db.de 1 rxn--berall-ist-8db.de 65535 test.org 655357 test.org 65536 test.org 1 example.comalpn=\"h3,h2\" ipv4hi-nt=\"192.0.2.1\" ipv6hint=\"2001:db8::1\" 678 tes\"\"t 1 test.org =\"test\" "; // 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/