example.ex

defmodule Example do

  def main(args) do
    args |> parse_args |> process
  end

  def parse_args(args) do
    options = OptionParser.parse(args, switches: [help: :boolean],
                                      aliases: [h: :help])
    case options do
      { [ help: true], _}         -> :help
      { _, [ vehicle ] }          -> [vehicle, "eels"]
      { _, [ vehicle, fish ] }    -> [vehicle, fish]
      _                           -> :help
    end
  end

  def process([vehicle, fish]) do
    IO.puts "My #{vehicle} is full of #{fish}."
  end

  def process(:help) do
    IO.puts """
      Usage:
        example [vehicle] [fish]

      Options:
        -h, [--help]      # Show this help message and quit.

      Description:
        Excuse me, dear Sir, are there fish in your vehicle?
    """
    System.halt(0)
  end

end