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NAME

      aio_write - asynchronous write to a file (REALTIME)
 

LIBRARY

      Standard C Library (libc, -lc)
 

SYNOPSIS

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

DESCRIPTION

      The aio_write() system call 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.
 

RESTRICTIONS

      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() system call to avoid passing bogus context information to the
      kernel.
 
      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
      error.
 

ERRORS

      The aio_write() system call will fail if:
 
      [EAGAIN]           The request was not queued because of system resource
                         limitations.
 
      [ENOSYS]           The aio_write() system call is not supported.
 
      The following conditions may be synchronously detected when the
      aio_write() system call is made, or asynchronously, at any time there‐
      after.  If they are detected at call time, aio_write() returns -1 and
      sets errno appropriately; otherwise the aio_return() system call 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]            The iocb->aio_fildes argument is invalid, or is not
                         opened for writing.
 
      [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() system call is per
write(2) system call, and the value returned by the aio_error() sys‐
write(2) system
      call, or one of:
 
      [EBADF]            The iocb->aio_fildes argument is invalid for writing.
 
      [ECANCELED]        The request was explicitly canceled via a call to
                         aio_cancel().
 
      [EINVAL]           The offset iocb->aio_offset would be invalid.
aio_suspend(2),
aio(4)
 

STANDARDS

      The aio_write() system call is expected to conform to the IEEE Std 1003.1
      (“POSIX.1”) standard.
 

HISTORY

      The aio_write() system call first appeared in FreeBSD 3.0.
 

AUTHORS

      This manual page was written by Wes Peters 〈wes@softweyr.com〉.
 

BUGS

      Invalid information in iocb->_aiocb_private may confuse the kernel.
 

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