Nokogiri

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Description

Nokogiri (鋸) is an HTML, XML, SAX, and Reader parser. Among Nokogiri's many features is the ability to search documents via XPath or CSS3 selectors.

Features

  • XML/HTML DOM parser which handles broken HTML
  • XML/HTML SAX parser
  • XML/HTML Push parser
  • XPath 1.0 support for document searching
  • CSS3 selector support for document searching
  • XML/HTML builder
  • XSLT transformer

Nokogiri parses and searches XML/HTML using native libraries (either C or Java, depending on your Ruby), which means it's fast and standards-compliant.

Installation

If this doesn't work:

gem install nokogiri

then please start troubleshooting here:

http://www.nokogiri.org/tutorials/installing_nokogiri.html

There are currently 1,237 Stack Overflow questions about Nokogiri installation. The vast majority of them are out of date and therefore incorrect. Please do not use Stack Overflow.

Instead, tell us when the above instructions don't work for you. This allows us to both help you directly and improve the documentation.

Binary packages

Binary packages are available for some distributions.

Support

There are open-source tutorials (to which we invite contributions!) here: http://nokogiri.org/tutorials

Synopsis

Nokogiri is a large library, but here is example usage for parsing and examining a document:

#! /usr/bin/env ruby

require 'nokogiri'
require 'open-uri'

# Fetch and parse HTML document
doc = Nokogiri::HTML(open('http://www.nokogiri.org/tutorials/installing_nokogiri.html'))

puts "### Search for nodes by css"
doc.css('nav ul.menu li a', 'article h2').each do |link|
  puts link.content
end

puts "### Search for nodes by xpath"
doc.xpath('//nav//ul//li/a', '//article//h2').each do |link|
  puts link.content
end

puts "### Or mix and match."
doc.search('nav ul.menu li a', '//article//h2').each do |link|
  puts link.content
end

Requirements

  • Ruby 2.1.0 or higher, including any development packages necessary to compile native extensions.

  • In Nokogiri 1.6.0 and later libxml2 and libxslt are bundled with the gem, but if you want to use the system versions:

    • First, check out the long list of fixes and changes between releases before deciding to use any version older than is bundled with Nokogiri.
    • At install time, set the environment variable NOKOGIRI_USE_SYSTEM_LIBRARIES or else use the --use-system-libraries argument. (See http://nokogiri.org/tutorials/installing_nokogiri.html#using_your_system_libraries for specifics.)
    • libxml2 >=2.6.21 with iconv support (libxml2-dev/-devel is also required)
    • libxslt, built with and supported by the given libxml2 (libxslt-dev/-devel is also required)

Encoding

Strings are always stored as UTF-8 internally. Methods that return text values will always return UTF-8 encoded strings. Methods that return a string containing markup (like to_xml, to_html and inner_html) will return a string encoded like the source document.

WARNING

Some documents declare one encoding, but actually use a different one. In these cases, which encoding should the parser choose?

Data is just a stream of bytes. Humans add meaning to that stream. Any particular set of bytes could be valid characters in multiple encodings, so detecting encoding with 100% accuracy is not possible. libxml2 does its best, but it can't be right all the time.

If you want Nokogiri to handle the document encoding properly, your best bet is to explicitly set the encoding. Here is an example of explicitly setting the encoding to EUC-JP on the parser:

  doc = Nokogiri.XML('<foo><bar /><foo>', nil, 'EUC-JP')

Development

  bundle install
  bundle exec rake

License

MIT. See the LICENSE.txt file.