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= cowboy:get_env(3)
== Name
cowboy:get_env - Retrieve a listener's environment value
== Description
[source,erlang]
----
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.
== Arguments
Name::
The name of the listener to access.
+
The name of the listener is the first argument given to the
link:man:cowboy:start_clear(3)[cowboy:start_clear(3)],
link:man:cowboy:start_tls(3)[cowboy:start_tls(3)] or
link:man:ranch:start_listener(3)[ranch:start_listener(3)] function.
Key::
The key in the environment map. Common keys include `dispatch`
and `middlewares`.
Default::
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.
== Changelog
* *2.11*: Function introduced.
== Examples
.Retrieve a listener's routes
[source,erlang]
----
Dispatch = cowboy:get_env(example, dispatch).
----
== See also
link:man:cowboy(3)[cowboy(3)],
link:man:cowboy:start_clear(3)[cowboy:start_clear(3)],
link:man:cowboy:start_tls(3)[cowboy:start_tls(3)],
link:man:cowboy:set_env(3)[cowboy:set_env(3)],
link:man:ranch:get_protocol_options(3)[ranch:get_protocol_options(3)]
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