_fsync is a version of fsync designed
to operate only on HFS files. _fsync runs faster and calls
fewer other library routines than fsync. The _fsync function is
used exactly like the standard fsync function. The argument
to _fsync must be the file descriptor for an open HFS file.
See fsync for a full description.
Copyright (c) 1998 SAS Institute Inc. Cary, NC, USA. All rights reserved.