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

/
/
gms

Test String

Code Generator

Generated Code

$re = '/^\s*(enum[^{]*)\s*({)\s*([^}]+)\s*(};)/ms'; $str = '#include <iostream> // enum that takes 16 bits enum smallenum: int16_t { a, b, c }; // color may be red (value 0), yellow (value 1), green (value 20), or blue (value 21) enum color { red, yellow, green = 20, blue }; // altitude may be altitude::high or altitude::low enum class altitude: char { high=\'h\', low=\'l\', // C++11 allows the extra comma }; // the constant d is 0, the constant e is 1, the constant f is 3 enum { d, e, f = e + 2 }; //enumeration types (both scoped and unscoped) can have overloaded operators std::ostream& operator<<(std::ostream& os, color c) { switch(c) { case red : os << "red"; break; case yellow: os << "yellow"; break; case green : os << "green"; break; case blue : os << "blue"; break; default : os.setstate(std::ios_base::failbit); } return os; } std::ostream& operator<<(std::ostream& os, altitude al) { return os << static_cast<char>(al); } int main() { color col = red; altitude a; a = altitude::low; std::cout << "col = " << col << \'\\n\' << "a = " << a << \'\\n\' << "f = " << f << \'\\n\'; }'; preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0); // Print the entire match result var_dump($matches);

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 PHP, please visit: http://php.net/manual/en/ref.pcre.php