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

/
/
gm

Test String

Code Generator

Generated Code

using System; using System.Text.RegularExpressions; public class Example { public static void Main() { string pattern = @"(?s) *(<sample [^>]*>.*?<\/ ?sample>)"; string input = @"<!DOCTYPE qhelp PUBLIC ""-//Semmle//qhelp//EN"" ""qhelp.dtd""> <qhelp> <overview> <p>The C++ <code>throw</code> expression can take several forms. One form throws a new exception, whereas the other re-throws the current exception. In the latter case, if there is no current exception, then the program will be terminated. Presence of a re-throw outside of an exception handling context is often caused by the programmer not knowing what kind of exception to throw.</p> </overview> <recommendation> <p>The <code>throw</code> expression should be changed to throw a particular type of exception.</p> </recommendation> <example> <sample language=""cpp""> void bad() { /* ... */ if(error_condition) throw; } void good() { /* ... */ if(error_condition) throw std::exception(""Something went wrong.""); } </sample> </example> <references> <li>Open Standards: <a href=""http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2012/n3337.pdf"">Standard for Programming Language C++, draft n3337</a> [except.throw], clause 9, page 380.</li> </references> </qhelp>"; RegexOptions options = RegexOptions.Multiline; foreach (Match m in Regex.Matches(input, pattern, options)) { Console.WriteLine("'{0}' found at index {1}.", m.Value, m.Index); } } }

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 C#, please visit: https://msdn.microsoft.com/en-us/library/system.text.regularexpressions.regex(v=vs.110).aspx