View Source Config (Elixir v1.10.0)
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.
config/2 and config/3 are used to define key-value configuration
for a given application. Once Mix starts, it will automatically
evaluate the configuration file and persist the configuration above
into :some_app's application environment, which can be accessed in
as follows:
"value1" = Application.fetch_env!(:some_app, :key1)Finally, the line import_config "#{Mix.env()}.exs" will import other
config files, based on the current Mix environment, such as
config/dev.exs and config/test.exs.
Config also provides a low-level API for evaluating and reading
configuration, under the Config.Reader module.
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(__DIR__) |> Path.wildcard() do
import_config config
endconfig/releases.exs
If you are using releases, see mix release, there is another configuration
file called config/releases.exs. While config/config.exs and friends
mentioned in the previous section are executed whenever you run a Mix
command, including when you assemble a release, config/releases.exs is
executed every time your production system boots. Since Mix is not available
in a production system, config/releases.exs must not use any of the
functions from Mix.
Link to this section Summary
Functions
Configures the given root_key.
Configures the given key for the given root_key.
Imports configuration from the given file.
Link to this section Functions
Configures the given root_key.
Keyword lists are always deep-merged.
Examples
The given opts are merged into the existing configuration
for the given root_key. Conflicting keys are overridden by the
ones specified in opts. For example, the application
configuration below
config :logger,
level: :warn,
backends: [:console]
config :logger,
level: :info,
truncate: 1024will have a final configuration for :logger of:
[level: :info, backends: [:console], truncate: 1024]Configures the given key for the given root_key.
Keyword lists are always deep merged.
Examples
The given opts are merged into the existing values for key
in the given root_key. Conflicting keys are overridden by the
ones specified in opts. For example, the application
configuration below
config :ecto, Repo,
log_level: :warn,
adapter: Ecto.Adapters.Postgres
config :ecto, Repo,
log_level: :info,
pool_size: 10will have a final value of the configuration for the Repo
key in the :ecto application of:
[log_level: :info, pool_size: 10, adapter: Ecto.Adapters.Postgres]Imports configuration from the given file.
In case the file doesn't exist, an error is raised.
If file is a relative, it will be expanded relatively to the directory the current configuration file is in.
Examples
This is often used to emulate configuration across environments:
import_config "#{Mix.env()}.exs"