escripts.md

layout	title	category	order	lang
page	Executables	advanced	3	en

To build executables in Elixir we will be using escript. Escript produces an executable that can be run on any system with Erlang installed.

Table of Contents

• Getting Started
• Parsing Args
• Building

Getting Started

To create an executable with escript there are only a few things we need to do: implement a main/1 method and update our Mixfile.

We'll start by creating a module to serve as the entry point to our executable, this is where we'll implement main/1:

defmodule ExampleApp.CLI do
  def main(args \\ []) do
    # Do stuff
  end
end

Next we need to update our Mixfile to include the :escript option for our project along with specifying our :main_module:

defmodule ExampleApp.Mixfile do
  def project do
    [app: :example_app,
     version: "0.0.1",
     escript: escript]
  end

  def escript do
    [main_module: ExampleApp.CLI]
  end
end

Parsing Args

With our application setup we can move on to parsing the command line arguments. To do this we'll use Elixir's OptionParser.parse/2 and the :switches option to indicate that our flag is boolean:

defmodule ExampleApp.CLI do
  def main(args \\ []) do
    args
    |> parse_args
    |> response
    |> IO.puts
  end

  defp parse_args(args) do
    {opts, word, _} =
      args
      |> OptionParser.parse(switches: [upcase: :boolean])

    {opts, List.to_string(word)}
  end

  defp response({opts, "Hello"}), do: response({opts, "World"})
  defp response({opts, word}) do
    if opts[:upcase], do: word = String.upcase(word)
    word
  end
end

Building

Once we've finished configuring our application to use escript, building our executable is a breeze with mix:

$ mix escript.build

Let's take it for a spin:

$ ./example_app --upcase Hello
WORLD

$ ./example_app Hi
Hi

That's it, we've built our first executable in Elixir using escript.