If a call to open() or creat() supplies
the third _mode_ parameter, it will
currently be ignored.
Most of the functionality of these functions depends on
the underlying filesystem.
Currently access() only checks the
F_OK mode explicitly, the others are
all assumed to be true by default.
The maximum number of open files allowed is supplied by
the CYGNUM_FILEIO_NFILE option. The maximum number
of file descriptors is supplied by the CYGNUM_FILEIO_NFD
option.