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)^(?=(?:\([^)]*\))*[^()\n]+[^@\n]*@)(?!(?:\([^)]*\))*\.)(?:(?:[\w!#$%&'*+/=?^`{|}~.-]|\([\w!#$%&'*+/=?^`{|}~.-]*\))+|"(?:[\w!#$%&'*+/=?^`{|}~.-]|\([\w!#$%&'*+/=?^`{|}~.-]*\))*")@(?:\([A-Za-z0-9-]*\))*(?:[A-Za-z0-9]+(?:(?:\([A-Za-z0-9-]*\))*-(?:\([A-Za-z0-9-]*\))*[A-Za-z0-9]+)*(?:\([A-Za-z0-9-]*\))*)(?:\.(?:\([A-Za-z0-9-]*\))*(?:[A-Za-z0-9]+(?:(?:\([A-Za-z0-9-]*\))*-(?:\([A-Za-z0-9-]*\))*[A-Za-z0-9]+)*(?:\([A-Za-z0-9-]*\))*))+$"#).unwrap(); let string = "************* VALID ************* a@a.a -@a.a a@1.a a@a-a.a a@a.a-a !#$%&'*+-/=?^_`{|}~@test.jp a..a@test.jp a..@test.jp \"a\"@test.jp \"\"@test.jp (comment)(comment)a(comment)(comment)(comment)@(comment)a.a (comment)(comment)a.(comment)(comment)(comment)@(comment)a.a (comment)(comment)a(comment).(comment)(comment)@(comment)a.a a@(comment)a(comment)-(comment)a(comment).a john.doe@(-comment)example.com john.doe@example.com(comment-) ()a@test.jp (a)a@test.jp a(a)@test.jp a@(a)test.jp a@test.jp(a) simple@example.com very.common@example.com disposable.style.email.with+symbol@example.com other.email-with-hyphen@example.com fully-qualified-domain@example.com user.name+tag+sorting@example.com x@example.com example-indeed@strange-example.com test/test@test.com example@s.example \"john..doe\"@example.org mailhost!username@example.org user%example.com@example.org user-@example.org 1@1234567890123456789012345678901234567890123456789012345678901234.1.2.3.4.5.6.7 a@a-a.a a@a-a-a.a a@a-a-a-a.a a@a-a-a.a-a-a ************* INVALID ************* a@a a@a. a@-a.a a@a-.a a@a.a- a@a.-a a;a@test.jp .a@test.jp \";\"@test.jp \"@\"@test.jp \"a@test.jp a\"@test.jp a\"\"@test.jp \"\"a@test.jp ()@test.jp )(a@test.jp (a)@test.jp (a@test.jp (())a@test.jp (comment)(comment).(comment)a(comment)(comment)@(comment)a.a john.doe@(comment).com a@(comment)a(comment)-(comment)(comment).a Αθήνα@email.com admin@mailserver1 \" \"@example.org \"very.(),:;<>[]\\\".VERY.\\\"very@\\\\ \\\"very\\\".unusual\"@strange.example.com postmaster@[123.123.123.123] postmaster@[IPv6:2001:0db8:85a3:0000:0000:8a2e:0370:7334] a,a@a.a "; // 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/