Unknown option: "-4" Unix manual page for aio. (host=minya system=Darwin)
AIO(4)                   BSD Kernel Interfaces Manual                   AIO(4)

NAME
     aio -- asynchronous I/O

DESCRIPTION
     The aio facility provides system calls for asynchronous I/O.

SEE ALSO
     aio_cancel(2), aio_error(2), aio_read(2), aio_return(2), aio_suspend(2),
     aio_write(2), lio_listio(2)

HISTORY
     The aio facility appeared in FreeBSD 3.0.

BSD                            February 16, 2006                           BSD