Snoop

Snoop on content, be notified when it changes.

Want to know when the next version of JRuby is released? Me too! Let's Snoop the JRuby homepage and print to the terminal when a new version has been posted. In this example, we'll check jruby.org every 5 minutes for a new version.

require 'snoop'

snoop = Snoop::HttpNotifier.new(
  url: 'http://jruby.org',
  css: '#latest_release strong'
)

snoop.notify while: -> { true }, delay: 300 do |version|
  puts "New JRuby Version! #{version}"
end

Snoop works really well with Mac OS X notifications. Install terminal-notifier and use it in your notify callback.

$ gem install terminal-notifier

Let's send Mac OS X notifications when people start watching our video on Confreaks. We'll use Snoop to check for updates every 2 minutes and send a notification if we get more views. In this example, the Snoop will run until the video has reached 2000 views, then stop.

require 'snoop'

video = '2291-larubyconf2013-impressive-ruby-productivity-with-vim-and-tmux'

snoop = Snoop::HttpNotifier.new(
  url: "http://www.confreaks.com/videos/#{video}",
  css: '.video-rating'
)

view_count = 0

snoop.notify until: -> { view_count >= 2000 }, delay: 120 do |video_rating|
  current_view_count = video_rating.gsub(/\D/, '').to_i
  new_view_count     = current_view_count - view_count
  view_count         = current_view_count

  message = "#{current_view_count} views (#{new_view_count} new) on your video!"

  puts "Sending notification: #{message}"
  `terminal-notifier -message "#{message}"`
end

Each Snoop requires a URL, but you can also provide a css selector if you're only interested in part of the page's content. The css selector you provide is handed directly to Nokogiri, so the same syntax is required.

require 'snoop'

# Receive notifications if any part of the page changes
snoop = Snoop::HttpNotifier.new(
  url: 'http://jruby.org'
)

# Receive notifications if just the latest JRuby release changes
snoop = Snoop::HttpNotifier.new(
  url: 'http://jruby.org',
  css: '#latest_release strong'
)

If you'd like to have your Snoop check for new content more than once, you can provided a count. Alternatively, you can use Conditional Snooping.

The count option is most useful for timeboxing a Snoop.

require 'snoop'
snoop = Snoop::HttpNotifier.new(url: 'http://jruby.org')

# Check JRuby for updates, every minute for 10 minutes
snoop.notify count: 10, delay: 60 do |content|
  puts content
end

By default, a Snoop will only check once and return immediately. This is almost useless since we are interested in change over time. Conditional Snooping is possible with the while and until arguments. It is almost always recommended to provide a delay when using conditional Snooping unless you are trying to DDoS someone.

Here's an example of a daemon Snoop that runs forever, checking the JRuby homepage every minute for changes.

require 'snoop'

snoop = Snoop::HttpNotifier.new(url: 'http://jruby.org')

snoop.notify while: -> { true }, delay: 60 do |content|
  puts content
end

Something else we might want to do is check our Twitter follower count. Here's an example that checks twitter every 3 minutes for changes. If the content changes, then we print our new follower count to the terminal. When we've reached 500 followers, the Snoop will stop checking.

require 'snoop'

snoop = Snoop::HttpNotifier.new(
  url: 'https://twitter.com/chrishunt',
  css: '[data-element-term="follower_stats"]'
)

follower_count = 0

snoop.notify until: -> { follower_count >= 500 }, delay: 180 do |content|
  follower_count = content.gsub(/\D/, '').to_i
  puts "You have #{follower_count} followers!"
end

Add this line to your application's Gemfile:

gem 'snoop'

And then execute:

$ bundle

Or install it yourself as:

$ gem install snoop

Please see the Contributing Document