Applications

An OTP application is a component with its own supervision tree, config, and lifecycle — your project and each dependency are applications.

An OTP application is a component with its own supervision tree, config, and lifecycle — your project and each dependency are applications.

priv/ directory holds non-code assets (SQL, static files, NIF binaries).

Callbacks: start/2, prep_stop/1, stop/1, config_change/3.

Library applications have no mod: (no supervision tree).

def application do
  [mod: {MyApp.Application, []}, extra_applications: [:logger]]
end

Application.start(:my_app), Application.stop(:my_app)
Application.ensure_all_started(:my_app)
Application.started_applications()
Application.spec(:my_app, :vsn)
Application.app_dir(:my_app, "priv/data.json")