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https://github.com/html-extract/hext

Domain-specific language for extracting structured data from HTML documents
https://github.com/html-extract/hext

cpp data-extraction dsl html html-extraction node php python ruby scraping

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Domain-specific language for extracting structured data from HTML documents

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README 

        
# Hext — Extract Data from HTML



[![PyPI Version](https://img.shields.io/pypi/v/hext.svg?color=blue)](https://pypi.org/project/hext/) [![npm version](https://img.shields.io/npm/v/hext.svg)](https://www.npmjs.com/package/hext)



Hext is a domain-specific language for extracting structured data from HTML documents.



Hext is written in C++ but language bindings are available for [Python](https://hext.thomastrapp.com/download#hext-for-python), [Node](https://hext.thomastrapp.com/download#hext-for-node), [JavaScript](https://hext.thomastrapp.com/download#hext-for-javascript), [Ruby](https://hext.thomastrapp.com/download#hext-for-ruby) and [PHP](https://hext.thomastrapp.com/download#hext-for-php).



![Hext Logo](https://raw.githubusercontent.com/html-extract/html-extract.github.io/master/hext-logo-x100.png)



See https://hext.thomastrapp.com for

[documentation](https://hext.thomastrapp.com/documentation), 

[installation instructions](https://hext.thomastrapp.com/download) and a live demo.



The Hext project is released under the terms of the Apache License v2.0.



## Example

Suppose you want to extract all hyperlinks from a web page. Hyperlinks have an

anchor tag <a>, an attribute called href and a text that visitors can

click. The following Hext template will produce a dictionary for every matched

element. Each dictionary will contain the keys `link` and `title` which refer

to the href attribute and the text content of the matched <a>.



    # Extract links and their text

    



[» Load example in editor](https://hext.thomastrapp.com/#attribute)



Visit [Hext's project page](https://hext.thomastrapp.com) to learn more about

Hext. For examples that use the libhext C++ library check out `/libhext/examples`

and

[libhext's C++ library overview](https://hext.thomastrapp.com/libhext-overview).



## Components of this Project

* `htmlext`: Command line utility that applies Hext templates to an HTML document

  and produces JSON.

* `libhext`: C++ library that contains a Hext parser but also allows for

  customization.

* `libhext-test`: Unit tests for libhext.

* `Hext bindings`: Bindings for scripting languages. There are extensions for

  Node.js, Python, Ruby and PHP that are able to parse Hext and extract values

  from HTML.



## Project layout

    ├── build             Build directory for htmlext

    ├── cmake             CMake modules used by the project

    ├── htmlext           Source for the htmlext command line tool

    ├── libhext           The libhext project

    │   ├── bindings      Hext bindings for scripting languages

    │   ├── build         Build directory for libhext

    │   ├── doc           Doxygen documentation for libhext

    │   ├── examples      Examples making use of libhext

    │   ├── include       Public libhext API

    │   ├── ragel         Ragel input files

    │   ├── scripts       Helper scripts for libhext

    │   ├── src           libhext implementation files

    │   └── test          The libhext-test project

    │       ├── build     Build directory for libhext-test

    │       └── src       Source for libhext-test

    ├── man               Htmlext man page

    ├── scripts           Scripts for building and testing releases

    ├── syntaxhl          Syntax highlighters for Vim and ACE

    └── test              Blackbox tests for htmlext



## Dependencies for development

* [Ragel](http://www.colm.net/open-source/ragel/) generates the state machine

  that is used to parse Hext

* The unit tests for libhext are written with

  [Google Test](https://github.com/google/googletest)

* libhext's public API documentation is generated by

  [Doxygen](http://www.stack.nl/~dimitri/doxygen/)

* libhext's scripting language bindings are generated by

  [Swig](http://www.swig.org/)



## Tests

There are unit tests for libhext and blackbox tests for Hext as a language,

whose main purpose is to detect unwanted change in syntax or behavior.  

The libhext-test project is located in `/libhext/test` and depends on Google

Test. Nothing fancy, just build the project and run the executable

`libhext-test`. How to write test cases with Google Test is described

[here](https://github.com/google/googletest/blob/master/googletest/docs/Primer.md).  

The blackbox tests are located in `/test`. There you'll find a shell script

called `blackbox.sh`. This script applies Hext templates to HTML documents and

compares the result to a third file that contains the expected output. For

example, there is a test case `icase-quoted-regex` that consists of three files:

`icase-quoted-regex.hext`, `icase-quoted-regex.html`, and

`icase-quoted-regex.expected`. To run this test case you would do the following:



    $ ./blackbox.sh case/icase-quoted-regex.hext



`blackbox.sh` will then look for the corresponding `.html` and `.expected` files

of the same name in the directory of `icase-quoted-regex.hext`. Then it will

invoke `htmlext` with the given Hext template and HTML document and compare the

result to `icase-quoted-regex.expected`. To run all blackbox tests in

succession:



    $ ./blackbox.sh case/*.hext



By default `blackbox.sh` will look for the `htmlext` binary in `$PATH`. Failing

that, it looks for the binary in the default build directory. You can tell

`blackbox.sh` which command to use by setting HTMLEXT. For example, to run all

tests through valgrind you'd run the following:



    $ HTMLEXT="valgrind -q ../build/htmlext" ./blackbox.sh case/*.hext



## Acknowledgements

* [Gumbo](https://github.com/google/gumbo-parser)

  — **An HTML5 parsing library in pure C99**  

  Gumbo is used as the HTML parser behind `hext::Html`. It's fast, easy to

  integrate and even fixes invalid HTML.

* [Ragel](http://www.colm.net/open-source/ragel/)

  — **Ragel State Machine Compiler**  

  The state machine that is used to parse Hext templates is generated by Ragel.

  You can find the definition of this machine in `/libhext/ragel/hext-machine.rl`.

* [RapidJSON](http://rapidjson.org/)

  — **A fast JSON parser/generator for C++**  

  RapidJSON powers the JSON output of the `htmlext` command line utility.

* [jq](https://stedolan.github.io/jq/)

  — **A lightweight and flexible command-line JSON processor**  

  An indispensable tool when dealing with JSON in the shell.

  Piping the output of `htmlext` into `jq` lets you do all sorts of crazy things.

* [Ace](https://ace.c9.io/) — **A Code Editor for the Web**  

  Used as the code editor in the

  "[Try Hext in your Browser!](https://hext.thomastrapp.com)" section and as a

  highlighter for all code examples. The highlighting rules for Hext are

  included in this project in `/syntaxhl/ace`. Also, there's a script in

  `/libhext/scripts/syntax-hl-ace` that uses Ace to transform a code template

  into highlighted HTML.

* [Boost.Beast](https://github.com/boostorg/beast)

  — **HTTP and WebSocket built on Boost.Asio in C++11**  

  The Websocket server behind the "[Try Hext in your Browser!](https://hext.thomastrapp.com)"

  section is built with Beast. See [github.com/html-extract/hext-on-websockets](https://github.com/html-extract/hext-on-websockets) for more.