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govconsvcs edited this page Sep 8, 2017 · 22 revisions

Nokogiri

Nokogiri is a simple HTML / XML parser with much of its interface borrowed from Hpricot. It uses libxml2 to parse and search, so it is very fast.

Installation

Installation is very easy. Just use the following command:

gem install nokogiri

Quick start to parsing HTML

Parsing HTML is easy, and you can take advantage of CSS selectors or XPath queries to find things in your document:

require 'open-uri'
require 'nokogiri'

# Perform a google search
doc = Nokogiri::HTML(open('http://google.com/search?q=tenderlove'))

# Print out each link using a CSS selector
doc.css('h3.r > a.l').each do |link|
  puts link.content
end

Here is an example parsing some HTML and searching it using a combination of CSS selectors and XPath selectors:

require 'nokogiri'

doc = Nokogiri::HTML.parse(<<-eohtml)
<html>
  <head>
    <title>Hello World</title>
  </head>
  <body>
    <h1>This is an awesome document</h1>
    <p>
      I am a paragraph
        <a href="http://google.ca">I am a link</a>
    </p>
  </body>
</html>
eohtml

####
# Search for nodes by css
doc.css('p > a').each do |a_tag|
  puts a_tag.content
end

####
# Search for nodes by xpath
doc.xpath('//p/a').each do |a_tag|
  puts a_tag.content
end

####
# Or mix and match.
doc.search('//p/a', 'p > a').each do |a_tag|
  puts a_tag.content
end

###
# Find attributes and their values
doc.search('a').first['href']

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