Do It - Subcommands and Single Binary CLI

In the last article, I introduced you to Do It, a library to create CLI tools in Elixir. Now, I'll show you the subcommands feature and how to generate a single binary using burrito-elixir.

Subcommands

Do It now supports subcommands; in this way, you can logically group other commands at any level using the subcomand macro.

For example:

defmodule HelloWorld.Template do
  use DoIt.Command,
    description: "Manage HelloWorld Template"

  subcommand(HelloWorld.Template.Set)
  subcommand(HelloWorld.Template.Unset)
  subcommand(HelloWorld.Template.Show)
end

When a command has subcommands, you cannot define arguments or options and don't need to implement the run callback function.

As I said before, it's just a way to group other commands logically but cleverly when implementing CLIs with many commands.

Calling parent command with the --help option shows all subcommands.

./hello_world template --help 

Usage: hello_world template SUBCOMMAND

Manage HelloWorld Template

Subcommands:
  show      Show default message template
  unset     Remove default message  template
  set       Set default message template

Run 'hello_world template SUBCOMMAND --help' for more information on a subcommand.

Single Binary

Do It supports single binary CLI distribution through burrito-elixir.

To configure the application, add the burrito-elixir dependency in your project, the :mod property in the application function, and the :releases key with the releases configuration to your project properties in your mix.exs file.

defmodule HelloWorld.MixProject do
  use Mix.Project

  def project do
    [
      app: :hello_world,
      version: "0.1.0",
      elixir: "~> 1.14",
      start_permanent: Mix.env() == :prod,
      deps: deps(),
      releases: releases()
    ]
  end

  # Run "mix help compile.app" to learn about applications.
  def application do
    [
      extra_applications: [:logger],
      mod: {HelloWorld, []}
    ]
  end

  # Run "mix help deps" to learn about dependencies.
  defp deps do
    [
      {:do_it, path: "../../"},
      {:burrito, github: "burrito-elixir/burrito"}
    ]
  end

  defp releases do
    [
      hello_world: [
        steps: [:assemble, &Burrito.wrap/1],
        burrito: [
          targets: [
            macos: [os: :darwin, cpu: :x86_64],
            linux: [os: :linux, cpu: :x86_64],
            windows: [os: :windows, cpu: :x86_64]
          ]
        ]
      ]
    ]
  end
end

After configurations, you can build using the mix release command, the binaries will be generated in burrito_out folder.

$ MIX_ENV=prod mix release
...
ls -l burrito_out
total 77208
-rwxr--r--  1 castilho  staff  16729320 Oct 27 16:23 hello_world_linux
-rwxr--r--  1 castilho  staff   6572904 Oct 27 16:22 hello_world_macos
-rwxr--r--  1 castilho  staff  16222208 Oct 27 16:24 hello_world_windows.exe

See the build process and CLI execution in the video below.