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

r"
"
gm

Test String

Code Generator

Language

Generated Code

$re = '/^[\s]{0,2}\[([\d]*)\]:/m'; $str = '--- # Meta Data Title: Test Set for Mark Down Reference Linking Summary: Test Set for Mark Down Reference Linking Author: Royi # Settings settings: enable_uml: true image_path_conversion: base64 markdown_extensions: - markdown.extensions.footnotes - markdown.extensions.fenced_code - markdown.extensions.tables - markdown.extensions.admonition - markdown.extensions.toc: title: Table of Contents toc_depth: 2-3 - pymdownx.arithmatex: generic: true smart_dollar: false allow_css_overrides: true --- # Test Set for Mark Down Reference Linking [TOC] ## Scope of the Document Just some text as a test set. ### Some ASCII Graphics Laser beam. ``` Target +--------------------------------+ | | | | | | | | | -- | | -/ | | --/ | | -/ | | --/ | +--------------------------------+ -/ --/ <-------------------/-----------------------> --/ -/ --/ +--------/ | -/| | -/ | | | Laser Beam +------+ ``` ## Some List * Train Set - Set used for training the ML model (For instance optimize the model parameters [For Parametric Model]) * Test Set - Set used to evaluate results. * Prediction - Prediction of velocity given a measurement. Implicit / Explicit Assumptions[^001]: * The laser beam is eye safe. * Just some information[^002]. ### Some Existing Links The results are pretty good in [RMSE][001] / [MAE][002]. ## Some Text to Test Free text, **bold text**, *italic text*, [__bold text__][003] or _italic text_. Also, `Mono Spaced Text` and regular [boring text][04]. Some [Link](https://www.wikipedia.com) and [Reference Link][1]. Some list... * Examining Deep Learning (DL) Based Methods Always some text on [Deep][1] Learning. * Hyper Parameters Adding an exhaustive search of the optimal Hyper Parameters. [001]: https://en.wikipedia.org/wiki/Root-mean-square_deviation "Wikipedia - RMSE" [002]: https://en.wikipedia.org/wiki/Mean_absolute_error "Wikipedia - MAE" [003]: https://something.com [04]: https://somewhere.com [5]: Should not be selected! [6]: Should not be selected! [^001]: Just a simple assumption reference. [^002]: Just another simple assumption reference. [1]: https://www.wikipedia.com'; 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