# Mix v1.10.3 mix escript.build View Source

Builds an escript for the project.

An escript is an executable that can be invoked from the command line. An escript can run on any machine that has Erlang/OTP installed and by default does not require Elixir to be installed, as Elixir is embedded as part of the escript.

This task guarantees the project and its dependencies are compiled and packages them inside an escript. Before invoking `mix escript.build`, it is only necessary to define a `:escript` key with a `:main_module` option in your `mix.exs` file:

    escript: [main_module: MyApp.CLI]

Escripts should be used as a mechanism to share scripts between developers and not as a deployment mechanism. For running live systems, consider using `mix run` or building releases. See the `Application` module for more information on systems life-cycles.

By default, this task starts the current application. If this is not desired, set the `:app` configuration to nil.

This task also removes documentation and debugging chunks from the compiled `.beam` files to reduce the size of the escript. If this is not desired, check the `:strip_beams` option.

> Note: escripts do not support projects and dependencies that need to store or read artifacts from the priv directory.

## Command line options

Expects the same command line options as `mix compile`.

## Configuration

The following option must be specified in your `mix.exs` under `:escript` key:

- `:main_module` - the module to be invoked once the escript starts. The module must contain a function named `main/1` that will receive the command line arguments. By default the arguments are given as a list of binaries, but if project is configured with `language: :erlang` it will be a list of charlists.

The remaining options can be specified to further customize the escript:

- `:name` - the name of the generated escript. Defaults to app name.

- `:path` - the path to write the escript to. Defaults to app name.

- `:app` - the app that starts with the escript. Defaults to app name. Set it to `nil` if no application should be started.

- `:strip_beams` - if `true` strips BEAM code in the escript to remove chunks unnecessary at runtime, such as debug information and documentation. Defaults to `true`.

- `:embed_elixir` - if `true` embeds Elixir and its children apps (`ex_unit`, `mix`, and the like) mentioned in the `:applications` list inside the `application/0` function in `mix.exs`.

  Defaults to `true` for Elixir projects, `false` for Erlang projects.

  Note: if you set this to `false` for an Elixir project, you will have to add paths to Elixir's `ebin` directories to `ERL_LIBS` environment variable when running the resulting escript, in order for the code loader to be able to find `:elixir` application and its children applications (if they are used).

- `:shebang` - shebang interpreter directive used to execute the escript. Defaults to `"#! /usr/bin/env escript\n"`.

- `:comment` - comment line to follow shebang directive in the escript. Defaults to `""`.

- `:emu_args` - emulator arguments to embed in the escript file. Defaults to `""`.

There is one project-level option that affects how the escript is generated:

- `language: :elixir | :erlang` - set it to `:erlang` for Erlang projects managed by Mix. Doing so will ensure Elixir is not embedded by default. Your app will still be started as part of escript loading, with the config used during build.

## Example

    defmodule MyApp.MixProject do
      use Mix.Project

      def project do
        [
          app: :my_app,
          version: "0.0.1",
          escript: escript()
        ]
      end

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

    defmodule MyApp.CLI do
      def main(_args) do
        IO.puts("Hello from MyApp!")
      end
    end