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aio_write - asynchronous write to a file (REALTIME)



      aio_write - asynchronous write to a file (REALTIME)


      Standard C Library (libc, -lc)


      #include <aio.h>
      aio_write(struct aiocb *iocb);


      The aio_write() function allows the calling process to write
      iocb->aio_nbytes from the buffer pointed to by iocb->aio_buf to the
      descriptor iocb->aio_fildes.  The call returns immediately after the
      write request has been enqueued to the descriptor; the write may or may
      not have completed at the time the call returns.  If the request could
      not be enqueued, generally due to invalid arguments, the call returns
      without having enqueued the request.
      If O_APPEND is set for iocb->aio_fildes, aio_write() operations append to
      the file in the same order as the calls were made.  If O_APPEND is not
      set for the file descriptor, the write operation will occur at the abso‐
      lute position from the beginning of the file plus iocb->aio_offset.
      If _POSIX_PRIORITIZED_IO is defined, and the descriptor supports it, then
      the enqueued operation is submitted at a priority equal to that of the
      calling process minus iocb->aio_reqprio.
      The iocb pointer may be subsequently used as an argument to aio_return()
      and aio_error() in order to determine return or error status for the
      enqueued operation while it is in progress.
      If the request is successfully enqueued, the value of iocb->aio_offset
      can be modified during the request as context, so this value must not be
      referenced after the request is enqueued.


      The Asynchronous I/O Control Block structure pointed to by iocb and the
      buffer that the iocb->aio_buf member of that structure references must
      remain valid until the operation has completed.  For this reason, use of
      auto (stack) variables for these objects is discouraged.
      The asynchronous I/O control buffer iocb should be zeroed before the
      aio_write() call to avoid passing bogus context information to the ker‐
      Modifications of the Asynchronous I/O Control Block structure or the
      buffer contents after the request has been enqueued, but before the
      request has completed, are not allowed.
      If the file offset in iocb->aio_offset is past the offset maximum  for
      iocb->aio_fildes, no I/O will occur.
      The aio_write() function returns the value 0 if successful; otherwise the
      value -1 is returned and the global variable errno is set to indicate the


      The aio_write() function will fail if:
      [EAGAIN]           The request was not queued because of system resource
      [ENOSYS]           The aio_write() call is not supported.
      The following conditions may be synchronously detected when the
      aio_write() call is made, or asynchronously, at any time thereafter.  If
      they are detected at call time, aio_write() returns -1 and sets errno
      appropriately; otherwise the aio_return() function must be called, and
      will return -1, and aio_error() must be called to determine the actual
      value that would have been returned in errno.
      [EBADF]            iocb->aio_fildes is invalid, or is not opened for
      [EINVAL]           The offset iocb->aio_offset is not valid, the priority
                         specified by iocb->aio_reqprio is not a valid prior‐
                         ity, or the number of bytes specified by
                         iocb->aio_nbytes is not valid.
      If the request is successfully enqueued, but subsequently canceled or an
      error occurs, the value returned by the aio_return() function is per the
      write(2) call, and the value returned by the aio_error() function is
      either one of the error returns from the write(2) call, or one of:
      [EBADF]            iocb->aio_fildes is invalid for writing.
      [ECANCELED]        The request was explicitly canceled via a call to
      [EINVAL]           The offset iocb->aio_offset would be invalid.


      aio_write() is expected to conform to the IEEE Std 1003.2 (“POSIX.2”)


      The aio_write Function first appeared in FreeBSD 3.0.


      This manual page was written by Wes Peters 〈〉.


      Asynchronous I/O operations cannot be canceled in this implementation.
      Invalid information in iocb->_aiocb_private may confuse the kernel.


Based on BSD UNIX
FreeBSD is an advanced operating system for x86 compatible (including Pentium and Athlon), amd64 compatible (including Opteron, Athlon64, and EM64T), UltraSPARC, IA-64, PC-98 and ARM architectures. It is derived from BSD, the version of UNIX developed at the University of California, Berkeley. It is developed and maintained by a large team of individuals. Additional platforms are in various stages of development.

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