Commands are not distinguished from options except for the fact that only one command is allowed.
stdin. The default mode is to create a socket and listen for commands there.
--daemon [command line
As an alternative you may create a new process as a child of
gpg-agent --daemon /bin/sh. This way you get a new
shell with the environment setup properly; after you exit from this
shell, gpg-agent terminates within a few seconds.