x                  The address of a null-terminated string
                       containing a name in UNIX style file
                       specification format.
    0                  Indicates that the filename is null or
                       syntactically incorrect.
    -1                 Indicates that the file specification contains
                       an ellipsis (for example, [ . . . ]a.dat), but
                       is otherwise correct. You cannot translate
                       the OpenVMS ellipsis syntax into a valid UNIX
                       style file specification.