select_demo.rb

#!/usr/bin/env ruby

require 'thread'

reader, writer = IO.pipe

t = Thread.new {
  loop {
    duration = rand(5) + 1
    sleep(duration)
    writer.write "slept for #{duration} seconds"
  }
}


puts "starting the select loop -- ctrl-c to quit"
puts "monitoring one side of an IO pipe, as well as STDIN"
puts "try typing in some input for STDIN..."

loop {
  # blocks until there is something to process
  #
  read_ios, write_ios, error_ios = select([reader, $stdin])

  read_ios.each { |ri|
    puts "#{ri} has something to read"
    puts "readpartial(255): #{ri.readpartial(255)}"
  }
}