gem "http"和"nokogiri"

• gem install http
• gem install nokogiri

require "http"
require "nokogiri"

#先获得网页内容
response = HTTP.get('https://www.baidu.com').body.to_s
#用Nokogiri转一下
doc = Nokogiri::HTML(response)
#现在可以分析了
doc.xpath('//*[@id="form"]/span[1]')