Regular Expressions 101

Save & Share

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

/
/
g

Test String

Code Generator

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#"(?<code1>id="question-summary-)(?<code2>\d+)"#).unwrap(); let string = "<div class=\"question-summary\" id=\"question-summary-80407\"> <div class=\"statscontainer\"> <div class=\"statsarrow\"></div> <div class=\"stats\"> <div class=\"vote\"> <div class=\"votes\"> <span class=\"vote-count-post \"><strong>2</strong></span> <div class=\"viewcount\">votes</div> </div> </div> <div class=\"status answered\"> <strong>1</strong>answer </div> </div> <div class=\"views \" title=\"60 views\"> 60 views </div> </div> <div class=\"summary\"> <h3><a href=\"/questions/80407/about-power-supply-of-opertional-amplifier\" class=\"question-hyperlink\">about power supply of opertional amplifier</a></h3> <div class=\"excerpt\"> I am constructing an operational amplifier as shown in the following figure. I use a batter as supplier for the OP Amp and set it up as a non-inverting amp circuit. I saw that the output was clipped ... </div> <div class=\"tags t-op-amp\"> <a href=\"/questions/tagged/op-amp\" class=\"post-tag\" title=\"show questions tagged 'op-amp'\" rel=\"tag\">op-amp</a> </div> <div class=\"started fr\"> <div class=\"user-info \"> <div class=\"user-action-time\"> asked <span title=\"2013-08-27 21:49:14Z\" class=\"relativetime\">11 hours ago</span> </div> <div class=\"user-gravatar32\"> <a href=\"/users/17060/user1285419\"><div class=\"\"><img src=\"https://www.gravatar.com/avatar/08ee68b20a4eceff26f7eee99b708c08?s=32&d=identicon&r=PG\" alt=\"\" width=\"32\" height=\"32\"></div></a> </div> <div class=\"user-details\"> <a href=\"/users/17060/user1285419\">user1285419</a><br> <span class=\"reputation-score\" title=\"reputation score\" dir=\"ltr\">165</span><span title=\"5 bronze badges\"><span class=\"badge3\"></span><span class=\"badgecount\">5</span></span> </div> </div> </div> </div> </div> <div class=\"question-summary\" id=\"question-summary-80405\"> <div class=\"statscontainer\"> <div class=\"statsarrow\"></div> <div class=\"stats\"> <div class=\"vote\"> <div class=\"votes\"> <span class=\"vote-count-post \"><strong>4</strong></span> <div class=\"viewcount\">votes</div> </div> </div> <div class=\"status answered-accepted\"> <strong>2</strong>answers </div> </div> <div class=\"views \" title=\"64 views\"> 64 views </div> </div> <div class=\"summary\"> <h3><a href=\"/questions/80405/5v-regulator-power-dissipation\" class=\"question-hyperlink\">5V Regulator Power Dissipation</a></h3> <div class=\"excerpt\"> I am using a 5V regulator (LP2950) from ON Semiconductor. I am using this for USB power and I'm feeding in 9V from an adapter. USB requires maximum of 500mA right? So the maximum power dissipation in ... </div> <div class=\"tags t-voltage-regulator t-surface-mount t-heatsink t-5v t-power-dissipation\"> <a href=\"/questions/tagged/voltage-regulator\" class=\"post-tag\" title=\"show questions tagged 'voltage-regulator'\" rel=\"tag\">voltage-regulator</a> <a href=\"/questions/tagged/surface-mount\" class=\"post-tag\" title=\"show questions tagged 'surface-mount'\" rel=\"tag\">surface-mount</a> <a href=\"/questions/tagged/heatsink\" class=\"post-tag\" title=\"show questions tagged 'heatsink'\" rel=\"tag\">heatsink</a> <a href=\"/questions/tagged/5v\" class=\"post-tag\" title=\"show questions tagged '5v'\" rel=\"tag\">5v</a> <a href=\"/questions/tagged/power-dissipation\" class=\"post-tag\" title=\"show questions tagged 'power-dissipation'\" rel=\"tag\">power-dissipation</a> </div> <div class=\"started fr\"> <div class=\"user-info \"> <div class=\"user-action-time\"> asked <span title=\"2013-08-27 21:39:31Z\" class=\"relativetime\">11 hours ago</span> </div> <div class=\"user-gravatar32\"> <a href=\"/users/10082/david-norman\"><div class=\"\"><img src=\"https://www.gravatar.com/avatar/8b073417e471077280b3fc5ff2eaf1f7?s=32&d=identicon&r=PG\" alt=\"\" width=\"32\" height=\"32\"></div></a> </div> <div class=\"user-details\"> <a href=\"/users/10082/david-norman\">David Norman</a><br> <span class=\"reputation-score\" title=\"reputation score\" dir=\"ltr\">322</span><span title=\"3 silver badges\"><span class=\"badge2\"></span><span class=\"badgecount\">3</span></span><span title=\"10 bronze badges\"><span class=\"badge3\"></span><span class=\"badgecount\">10</span></span> </div> </div> </div> </div> </div>"; // 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/