A really simple command-line Ruby application, for https://monospacedmonologues.com/2016/02/docker-part-three-running-software/.

Dockerfile

FROM ruby

RUN mkdir /app
WORKDIR /app

COPY Gemfile Gemfile
RUN bundle install

COPY google.rb google.rb
RUN chmod +x google.rb
ENTRYPOINT ["./google.rb"]
CMD ["docker"]

Gemfile

source 'https://rubygems.org'

gem 'nokogiri'

google.rb

#!/usr/bin/env ruby

require 'cgi'
require 'nokogiri'
require 'open-uri'

query = ARGV[0]
html = open("https://google.com/search?q=#{CGI.escape(query)}") { |io|
  Nokogiri::HTML(io)
}
results = html.css('.g')
results.each do |result|
  header = result.at_css('h3')
  puts header.text if header
end