Adds file to the list of keyrings used during processings. If file begins with a tilde and a slash, these are replaced by the HOME directory. If the filename does not contain a slash, it is assumed to be in the home directory. The home directory is ``~/.gnupg'' if the option homedir is not used.
The filename file may also be prefixed with a scheme. The scheme ``gnupg-ring:'' makes the specified file the default keyring. The scheme ``gnupg-gdbm:'' makes the specified file the GDBM ring. It may be useful to use these schemes together with the option no-default-keyring.