hello.rb

#!/usr/bin/env ruby

require 'optparse'
require 'yaml'
require 'date'

class Parser
  def self.parse_options(args)
    options = {}
    opt_parser = OptionParser.new do |opts|
      opts.banner = "Greets whoever is identified by data.yml."
      opts.separator "Will use the cowsay program, if it is installed."
      opts.separator "Usage: hello.rb [options]"
      opts.on("-c", "--cow COW", "Show message using cow type COW") do |c|
        options["cow"] = c
      end
      opts.on("-h", "--help", "Prints this help") do
        puts opts
        exit
      end
    end
    opt_parser.parse!(args)
    return options
  end
end

class Greeting
  def self.greet
    case DateTime.now.hour
    when 0..11
      "Good morning"
    when 12..16
      "Good afternoon"
    else
      "Good evening"
    end
  end
end

class MaybeCow
  def self.command?(command)
    system("which #{command} > /dev/null 2>&1")
  end

  def self.program(options)
    primary = "/usr/games/cowsay"
    alt     = "/usr/bin/tee"
    if command?(primary)
      options["cow"] ? "#{primary} -f #{options["cow"]}" : primary
    else
      alt
    end
  end
end

options = Parser.parse_options(ARGV)
data = YAML.load_file('data.yml')
name = 
  if data["first"]
    "#{data["first"]} #{data["last"]} (#{ENV["USER"]})"
  else
    "fine human being"
  end

IO.popen(MaybeCow.program(options), "w") do |c|
  c.puts "#{Greeting.greet} #{name}!"
  c.close
  puts
end