sys_flock —
flock system call.
long sys_flock (unsigned int fd, unsigned int cmd);
Apply a FL_FLOCK style lock to an open file descriptor.
The cmd can be one of
LOCK_SH -- a shared lock.
LOCK_EX -- an exclusive lock.
LOCK_UN -- remove an existing lock.
LOCK_MAND -- a `mandatory' flock. This exists to emulate Windows Share Modes.
LOCK_MAND can be combined with LOCK_READ or LOCK_WRITE to allow other
processes read and write access respectively.