Specs

whereis(server()) :: pid() | {atom(), node()} | nil

Returns the pid or {name, node} of a GenServer process, nil otherwise.

To be precise, nil is returned whenever a pid or {name, node} cannot be returned. Note there is no guarantee the returned pid or {name, node} is alive, as a process could terminate immediately after it is looked up.

Examples

For example, to lookup a server process, monitor it and send a cast to it:

process = GenServer.whereis(server)
monitor = Process.monitor(process)
GenServer.cast(process, :hello)