A simple keyword-based configuration API.

Example

This module is most commonly used to define application configuration, typically in config/config.exs:

import Config

config :some_app,
  key1: "value1",
  key2: "value2"

import_config "#{Mix.env()}.exs"

import Config will import the functions config/2, config/3 and import_config/1 to help you manage your configuration.

Once Mix starts, it will automatically evaluate the configuration file and persist it into :some_app's application environment, which can be accessed in as follows:

"value1" = Application.fetch_env!(:some_app, :key1)

See Config.Reader for evaluating and reading configuration files.

Important: if you are writing a library to be used by other developers, it is generally recommended to avoid the application environment, as the application environment is effectively a global storage. For more information, read our library guidelines.

Migrating from use Mix.Config

The Config module in Elixir was introduced in v1.9 as a replacement to Mix.Config, which was specific to Mix and has been deprecated.

You can leverage Config instead of Mix.Config in two steps. The first step is to replace use Mix.Config at the top of your config files by import Config.

The second is to make sure your import_config/1 calls do not have a wildcard character. If so, you need to perform the wildcard lookup manually. For example, if you did:

import_config "../apps/*/config/config.exs"

It has to be replaced by:

for config <- "apps/*/config/config.exs" |> Path.expand() |> Path.wildcard() do
  import_config config
end