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 = '/(?:[!]\[(?P<caption>.*?)\])\((?P<image>.*?)\)/m'; $str = 'This is a regex to detect markdown image links of the form ![image caption](image URL) Here are some markdown links - [pandoc-fignos](https://github.com/tomduck/pandoc-fignos): Numbers figures and figure references. The images section will walk you through how to add and reference images so that the pandoc system can properly number them. For example, this [figure](./ch0_1_images.md#fig:ch0_1_images-1) illustrates a VOD curve for a packaged watergel explosive and this [figure](./ch0_1_images.md#fig:ch0_1_images-2) depicts a circular arc. ## [Equations](./ch0_2_equations.md#sec:ch0_2_equations-1) The equations section will discuss how to use equations and reference them properly. See the [internal energy equation](./ch0_2_equations.md#eq:ch0_2_equations-1) or the [detonation pressure](./ch0_2_equations.md#eq:ch0_2_equations-2) This string does not contain any links Here are some image links: ![Caption.](image.png){#fig:id} ![Caption.](image.png){#fig:id tag="B.1"} ![This is a sample image representing the VOD curve of a packaged Watergel explosive.](../assets/1v6C9yek3pHsXSeOlR4glzDMkFqFHizR6VXr79tEOnY=.png){#fig:ch0_1_images-1 width=100%} ![](../../assets/E5WnRoSH_Dqrzl8f5_ZJ9AjWc-53BgiBqD_xTqEp6pM=.png) ![](../../assets/l2mxAo3IR1dc3Wrgt7Ulqhcm_8nwqFw5UY7pUI3X0oI=.png) ![](../../assets/Y7jjv0ceQH5Ew5O32U2Z_N7ARBfKn2FnHnUoUt_DYbA=.png) ![](../../assets/eOvy-JcdA7pjoDJS4rIgG5RgDfYJ4PY11Owbgy5DHWM=.png) ![](../../assets/XwMrG0o__iLF5nStoSPUuJ81ffxafRBWAVnEcGo10Yo=.png) ![](../../assets/AfHKsc518nK6Ew2MHJt96lJMkTiVAyIiuva6L-lRQaQ=.png) ![](../../assets/JyDHFl6DyL1mw5EI-pSb9ssNzmbsEaSPQn5AOiZqeiM=.png) ![](../../assets/BYGvFWn41qFZuU3C7Jyd1uHjs8Cib8eEJod0sIze9S0=.png) ![](../../assets/77U97Em8AN06LCGVxH6UQ_Lh3OZkNsJRkMZY1nBMVrA=.png) ![](../../assets/iPkPth_Vh_wSgeD0wqxlctDyDEmgHfYuhTqBQE6mynI=.png) ![](../../assets/h57_b4_XeFd5SR1iYLu9WsYNy_n8sM6rPbQdGephk1c=.png) ![](../../assets/u8Y_44VG3-pD8fweuazkSN9fflhJfgCqOtc2ooP2sVM=.png) ![](../../assets/dc-ExOEXIWnH0qwVHTSNmFljUwyKS0xeEYFxS98ZEYg=.png) ![](../../assets/nJZLBZEOCiOT2P1F2c5mVQZrCrIJB5i1EnRgT767WWo=.png) ![](../../assets/ilG_dm7Lr3315RFsUdJCW7tkJbTZlnmV_NNKFBDeyxc=.png) ![](../../assets/1v6C9yek3pHsXSeOlR4glzDMkFqFHizR6VXr79tEOnY=.png) ![](../../assets/Bw1eWhlyutzMa8Eg94-VnSk_TsffrBLeoZKWySkMwIw=.png) ![](../../assets/9RIkA4mInkKNSIxMi7ctUozBJPUqlHPugIfG2yr37Co=.png) ![Hyperbola](../../assets/300px-Hyperbola_properties.svg.png) ![Hyperbola](../../assets/HyperbolaAnatomyLeft.png) ![Hyperbola](../../assets/HyperbolaAnatomyRight.png) ![](../../assets/IsXLnPl1wKraeLnryg2rOxtYdGSSHg8vTTN1ObV0Dt8=.png)'; 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