EventMachine Pipe Clinet/Server

pipe-client.rb

#!/usr/bin/env ruby

require 'pathname'

uri = ARGV[0] || (puts "usage: #{$0} <uri>"; exit 1)

Pathname.new('pipe').open("w") do |fd|
  fd.puts(uri)
end

pipe-sever.rb

#!/usr/bin/env ruby

require 'digest'
require 'fcntl'
require 'em-http'
require 'pathname'
require 'addressable/uri'

class PipeServer < EventMachine::FileWatch

  def notify_readable
    data = @io.readlines
    data.each do |line|
      uri = Addressable::URI.parse(line.strip)

      if uri.scheme && uri.host
        puts "Fetching: #{uri.to_s}"
        http = EventMachine::HttpRequest.new(uri.to_s).get(:redirects => 5)

        http.callback do
          if http.response_header.status == 200
            path = Pathname.new("#{uri.scheme}.#{uri.host}.#{Digest::SHA1.hexdigest(http.response)}")
            path.open("w") { |fd| fd.write(http.response) }
            puts "Written output to: #{path.to_s}"
          else
            puts "Something went wrong: #{http.response_header.status}"
          end
        end

        http.errback do
          puts "Problem:", http.inspect
        end
      else
        puts "That's not a proper url."
      end
    end
  end

  def unbind
    puts "#{path} monitoring ceased"
    EM.stop
  end
end

EM.run {
  fd = IO.sysopen('pipe', Fcntl::O_RDONLY|Fcntl::O_NONBLOCK)

  pipe = IO.new(fd, Fcntl::O_RDONLY|Fcntl::O_NONBLOCK)
  fdmon = EM.watch(pipe, PipeServer)
  fdmon.notify_readable = true
}

Create a named pipe: mknod pipe p. Start the pipe server: ./pipe-server, and then run ./pipe-client <uri>. The uri will be downloaded and saved in the current directory. The client is just there for show; you could just use echo: echo <uri> > pipe

Note lines 45--51 are from this gist: https://gist.github.com/1141924