Updated: 2021/Apr/14

AIO_FSYNC(3)               Library Functions Manual               AIO_FSYNC(3)

     aio_fsync - asynchronous data synchronization of file (REALTIME)

     POSIX Real-time Library (librt, -lrt)

     #include <aio.h>

     aio_fsync(int op, struct aiocb *aiocbp);

     The aio_fsync() system call allows the calling process to force all
     modified data associated with the file descriptor aiocbp->aio_fildes to
     be flushed to the stable storage device.  The call returns immediately
     after the synchronization request has been enqueued to the descriptor;
     the synchronization 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.

     The op argument could be set only to O_DSYNC or O_SYNC.  If op is
     O_DSYNC, then aio_fsync() does the same as a fdatasync() call, if O_SYNC,
     then the same as fsync().

     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 aiocbp->aio_reqprio.

     The aiocbp 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.

     The aio_fsync() 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_fsync() system call will fail if:

     [EAGAIN]           The request was not queued because of system resource

     The following conditions may be synchronously detected when the
     aio_fsync() system call is made, or asynchronously, at any time
     thereafter.  If they are detected at call time, aio_fsync() 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 aiocbp->aio_fildes is invalid for writing.

     [EINVAL]           This implementation does not support synchronized I/O
                        for this file, or the op argument is neither set to
                        O_DSYNC nor O_SYNC.

     fcntl(2), fdatasync(2), fsync(2), aio(3)

     The aio_fsync() system call is expected to conform to the IEEE Std
     1003.1-2001 ("POSIX.1") standard.

     The aio_fsync() system call first appeared in NetBSD 5.0.

NetBSD 9.99                      May 17, 2010                      NetBSD 9.99