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)^v=spf1( +([-+?~]?(all|include:(%\{[CDHILOPR-Tcdhilopr-t]([1-9][0-9]?|10[0-9]|11[0-9]|12[0-8])?r?[+-\/=_]*\}|%%|%_|%-|[!-$&-~])*(\.([A-Za-z]|[A-Za-z]([-0-9A-Za-z]?)*[0-9A-Za-z])|%\{[CDHILOPR-Tcdhilopr-t]([1-9][0-9]?|10[0-9]|11[0-9]|12[0-8])?r?[+-\/=_]*\})|a(:(%\{[CDHILOPR-Tcdhilopr-t]([1-9][0-9]?|10[0-9]|11[0-9]|12[0-8])?r?[+-\/=_]*\}|%%|%_|%-|[!-$&-~])*(\.([A-Za-z]|[A-Za-z]([-0-9A-Za-z]?)*[0-9A-Za-z])|%\{[CDHILOPR-Tcdhilopr-t]([1-9][0-9]?|10[0-9]|11[0-9]|12[0-8])?r?[+-\/=_]*\}))?((\/(\d|1\d|2\d|3[0-2]))?(\/\/([1-9][0-9]?|10[0-9]|11[0-9]|12[0-8]))?)?|mx(:(%\{[CDHILOPR-Tcdhilopr-t]([1-9][0-9]?|10[0-9]|11[0-9]|12[0-8])?r?[+-\/=_]*\}|%%|%_|%-|[!-$&-~])*(\.([A-Za-z]|[A-Za-z]([-0-9A-Za-z]?)*[0-9A-Za-z])|%\{[CDHILOPR-Tcdhilopr-t]([1-9][0-9]?|10[0-9]|11[0-9]|12[0-8])?r?[+-\/=_]*\}))?((\/(\d|1\d|2\d|3[0-2]))?(\/\/([1-9][0-9]?|10[0-9]|11[0-9]|12[0-8]))?)?|ptr(:(%\{[CDHILOPR-Tcdhilopr-t]([1-9][0-9]?|10[0-9]|11[0-9]|12[0-8])?r?[+-\/=_]*\}|%%|%_|%-|[!-$&-~])*(\.([A-Za-z]|[A-Za-z]([-0-9A-Za-z]?)*[0-9A-Za-z])|%\{[CDHILOPR-Tcdhilopr-t]([1-9][0-9]?|10[0-9]|11[0-9]|12[0-8])?r?[+-\/=_]*\}))?|ip4:([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])\.([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])\.([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])\.([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])(\/([0-9]|1[0-9]|2[0-9]|3[0-2]))?|ip6:(::|([0-9A-Fa-f]{1,4}:){7}[0-9A-Fa-f]{1,4}|([0-9A-Fa-f]{1,4}:){1,8}:|([0-9A-Fa-f]{1,4}:){7}:[0-9A-Fa-f]{1,4}|([0-9A-Fa-f]{1,4}:){6}(:[0-9A-Fa-f]{1,4}){1,2}|([0-9A-Fa-f]{1,4}:){5}(:[0-9A-Fa-f]{1,4}){1,3}|([0-9A-Fa-f]{1,4}:){4}(:[0-9A-Fa-f]{1,4}){1,4}|([0-9A-Fa-f]{1,4}:){3}(:[0-9A-Fa-f]{1,4}){1,5}|([0-9A-Fa-f]{1,4}:){2}(:[0-9A-Fa-f]{1,4}){1,6}|[0-9A-Fa-f]{1,4}:(:[0-9A-Fa-f]{1,4}){1,7}|:(:[0-9A-Fa-f]{1,4}){1,8}|([0-9A-Fa-f]{1,4}:){6}([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])\.([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])\.([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])\.([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])|([0-9A-Fa-f]{1,4}:){6}:([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])\.([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])\.([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])\.([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])|([0-9A-Fa-f]{1,4}:){5}:([0-9A-Fa-f]{1,4}:)?([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])\.([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])\.([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])\.([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])|([0-9A-Fa-f]{1,4}:){4}:([0-9A-Fa-f]{1,4}:){0,2}([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])\.([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])\.([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])\.([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])|([0-9A-Fa-f]{1,4}:){3}:([0-9A-Fa-f]{1,4}:){0,3}([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])\.([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])\.([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])\.([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])|([0-9A-Fa-f]{1,4}:){2}:([0-9A-Fa-f]{1,4}:){0,4}([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])\.([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])\.([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])\.([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])|[0-9A-Fa-f]{1,4}::([0-9A-Fa-f]{1,4}:){0,5}([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])\.([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])\.([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])\.([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])|::([0-9A-Fa-f]{1,4}:){0,6}([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])\.([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])\.([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])\.([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5]))(\/(\d{1,2}|10[0-9]|11[0-9]|12[0-8]))?|exists:(%\{[CDHILOPR-Tcdhilopr-t]([1-9][0-9]?|10[0-9]|11[0-9]|12[0-8])?r?[+-\/=_]*\}|%%|%_|%-|[!-$&-~])*(\.([A-Za-z]|[A-Za-z]([-0-9A-Za-z]?)*[0-9A-Za-z])|%\{[CDHILOPR-Tcdhilopr-t]([1-9][0-9]?|10[0-9]|11[0-9]|12[0-8])?r?[+-\/=_]*\}))|redirect=(%\{[CDHILOPR-Tcdhilopr-t]([1-9][0-9]?|10[0-9]|11[0-9]|12[0-8])?r?[+-\/=_]*\}|%%|%_|%-|[!-$&-~])*(\.([A-Za-z]|[A-Za-z]([-0-9A-Za-z]?)*[0-9A-Za-z])|%\{[CDHILOPR-Tcdhilopr-t]([1-9][0-9]?|10[0-9]|11[0-9]|12[0-8])?r?[+-\/=_]*\})|exp=(%\{[CDHILOPR-Tcdhilopr-t]([1-9][0-9]?|10[0-9]|11[0-9]|12[0-8])?r?[+-\/=_]*\}|%%|%_|%-|[!-$&-~])*(\.([A-Za-z]|[A-Za-z]([-0-9A-Za-z]?)*[0-9A-Za-z])|%\{[CDHILOPR-Tcdhilopr-t]([1-9][0-9]?|10[0-9]|11[0-9]|12[0-8])?r?[+-\/=_]*\})|[A-Za-z][-.0-9A-Z_a-z]*=(%\{[CDHILOPR-Tcdhilopr-t]([1-9][0-9]?|10[0-9]|11[0-9]|12[0-8])?r?[+-\/=_]*\}|%%|%_|%-|[!-$&-~])*))* *$").unwrap(); let string = "# Valid SPF records v=spf1 -all v=spf1 a -all v=spf1 a mx -all v=spf1 +a +mx -all v=spf1 mx -all v=spf1 -all v=spf1 +all v=spf1 ip4:192.168.0.1/16 -all v=spf1 ip6:1080::8:800:200C:417A/96 -all v=spf1 ip6:1080::8:800:68.0.3.1/96 -all v=spf1 a:example.com -all v=spf1 a:mailers.example.com -all v=spf1 a/24 a:offsite.example.com/24 -all v=spf1 mx mx:deferrals.domain.com -all v=spf1 mx/24 mx:offsite.domain.com/24 -all v=spf1 ptr -all v=spf1 ptr:otherdomain.com -all v=spf1 exists:example.com -all v=spf1 include:example.com -all v=spf1 ?include:example.com -all v=spf1 redirect=example.com v=spf1 exp=example.com # None Valid SPF v=spf1 *all v=spf1 a-all v=spf1 aa mx -all v=spf1 +a +mx -alll v=spf1 mxx -all v=spf1 -all v=spf1+all v=spf1 ip4:192.168.0.1111/16 -all v=spf1 ipv6:1080::8:800:200C:417A/96 -all v=spf1 ip6:1080::8:800:68.0.3.1/96 -alll # com-all shoudl give an error, but it doesn't, need to fix this. v=spf1 a:example.com-all v=spf1 aa:mailers.example.com -all v=spf1 a/2a4 a:offsite.example.com/24 -all v=spf1 xmx mx:deferrals.domain.com -all v=spf1mx/24 mx:offsite.domain.com/24 -all ptr -all v=spf2 ptr:otherdomain.com -all v=spf1 existss:example.com -all v=spf1 include :example.com -all v=spf1 ?includes:example.com -all v=spf1 redirect=example.com v=spf1 exp=example.com"; // 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/