F_GETOWN = 9, // Get owner of socket (receiver of SIGIO).
F_SETSIG = 10, // Set number of signal to be sent.
F_GETSIG = 11, // Get number of signal to be sent.
+ F_NOCACHE = 48, // OSX: turn data caching off/on for this fd.
F_SETLEASE = 1024, // Set a lease.
F_GETLEASE = 1025, // Enquire what lease is active.
F_NOTIFY = 1026, // Required notifications on a directory