Specifies the name of the X authority file. Version numbers
    are not allowed. If a display device is specified on the
    command line, xauth will use the X authority file referenced
    by the display device. Otherwise, xauth will use the default X
    authority file used by client applications. This file is the X
    authority file referenced by the DECW$DISPLAY display device, the
    DECW$XAUTHORITY logical, or SYS$LOGIN:DECW$XAUTHORITY.DECW$XAUTH.