cowboy:get_env - Retrieve a listener's environment value


get_env(Name :: ranch:ref(),
        Key  :: atom())
    -> any()

get_env(Name    :: ranch:ref(),
        Key     :: atom(),
        Default :: any())
    -> any()

Retrieve an environment value for a previously started listener.

This function may crash when the key is missing from the environment and a default value is not provided.



The name of the listener to access.

The name of the listener is the first argument given to the cowboy:start_clear(3), cowboy:start_tls(3) or ranch:start_listener(3) function.


The key in the environment map. Common keys include dispatch and middlewares.


The default value if the key is missing.

Return value

The environment value is returned on success.

If a default was provided and the key is missing, then the default value is returned.

An exit:badarg exception is thrown when the listener does not exist.

An exit:{badkey, Key} exception is thrown when the key requested is missing and no default was provided.


  • 2.11: Function introduced.


Retrieve a listener's routes
Dispatch = cowboy:get_env(example, dispatch).

See also

cowboy(3), cowboy:start_clear(3), cowboy:start_tls(3), cowboy:set_env(3), ranch:get_protocol_options(3)

Cowboy 2.11 Function Reference


Version select

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