aio_return —
    retrieve return status of asynchronous I/O operation
    (REALTIME)
Standard C Library (libc, -lc)
#include
  <aio.h>
ssize_t
  
  aio_return(struct
    aiocb *iocb);
The
    aio_return()
    system call returns the final status of the asynchronous I/O request
    associated with the structure pointed to by iocb.
The
    aio_return()
    system call should only be called once, to obtain the final status of an
    asynchronous I/O operation once it has completed
    (aio_error(2)
    returns something other than EINPROGRESS).
If the asynchronous I/O request has completed, the status is
    returned as described in
    read(2),
    readv(2),
    write(2),
    writev(2),
    or
    fsync(2).
    Otherwise, aio_return() returns -1 and sets
    errno to indicate the error condition.
The aio_return() system call will fail
  if:
  - [EINVAL]
- The iocb argument does not reference a completed
      asynchronous I/O request.
- [EINVAL]
- The I/O operation was submitted with lio_listio(),
      and the value of the aio_lio_opcode is invalid.
The aio_return() system call is expected
    to conform to the IEEE Std 1003.1
    (“POSIX.1”) standard.
The aio_return() system call first
    appeared in FreeBSD 3.0.