mix.exs

defmodule Shell.Mixfile do
  use Mix.Project

  def project do
    [
      app: :shell,
      version: "0.0.1",
      elixir: "~> 1.0",
      deps: deps,
      escript: [
        app: nil,
        main_module: Shell,
        emu_args: "-noinput",
        consolidate_protocols: false
      ]
    ]
  end

  # Configuration for the OTP application
  #
  # Type `mix help compile.app` for more information
  def application do
    [applications: [:logger]]
  end

  # Dependencies can be Hex packages:
  #
  #   {:mydep, "~> 0.3.0"}
  #
  # Or git/path repositories:
  #
  #   {:mydep, git: "https://github.com/elixir-lang/mydep.git", tag: "0.1.0"}
  #
  # Type `mix help deps` for more examples and options
  defp deps do
    []
  end
end

shell.ex

defmodule Shell do

  def main(_) do
    :user_drv.start([:'tty_sl -c -e',{__MODULE__,:start_loop,[]}])
    :timer.sleep :infinity
  end

  def start_loop, do: spawn_link(&loop/0)

  def loop() do
    read |> eval |> print
    loop
  end

  def read() do
    IO.gets("Myprompt> ")
    |> parse
  end

  def eval(["echo" | stuff]), do: stuff
  def eval([cmd|_]) do
    IO.puts "Unknown command #{inspect cmd}"
    nil
  end
  def eval([]), do: nil

  def print(value) do
    IO.inspect value
  end

  defp parse(stmt), do: stmt |> to_string |> String.split

end