AIO_FSYNC(P) POSIX Programmer's Manual AIO_FSYNC(P)
aio_fsync - asynchronous file synchronization (REALTIME)
int aio_fsync(int op, struct aiocb *aiocbp);
The aio_fsync() function shall asynchronously force all I/O operations associated with the
file indicated by the file descriptor aio_fildes member of the aiocb structure referenced
by the aiocbp argument and queued at the time of the call to aio_fsync() to the synchro-
nized I/O completion state. The function call shall return when the synchronization
request has been initiated or queued to the file or device (even when the data cannot be
If op is O_DSYNC, all currently queued I/O operations shall be completed as if by a call
to fdatasync(); that is, as defined for synchronized I/O data integrity completion. If op
is O_SYNC, all currently queued I/O operations shall be completed as if by a call to
fsync(); that is, as defined for synchronized I/O file integrity completion. If the
aio_fsync() function fails, or if the operation queued by aio_fsync() fails, then, as for
fsync() and fdatasync(), outstanding I/O operations are not guaranteed to have been com-
If aio_fsync() succeeds, then it is only the I/O that was queued at the time of the call
to aio_fsync() that is guaranteed to be forced to the relevant completion state. The com-
pletion of subsequent I/O on the file descriptor is not guaranteed to be completed in a
The aiocbp argument refers to an asynchronous I/O control block. The aiocbp value may be
used as an argument to aio_error() and aio_return() in order to determine the error status
and return status, respectively, of the asynchronous operation while it is proceeding.
When the request is queued, the error status for the operation is [EINPROGRESS]. When all
data has been successfully transferred, the error status shall be reset to reflect the
success or failure of the operation. If the operation does not complete successfully, the
error status for the operation shall be set to indicate the error. The aio_sigevent mem-
ber determines the asynchronous notification to occur as specified in Signal Generation
and Delivery when all operations have achieved synchronized I/O completion. All other mem-
bers of the structure referenced by aiocbp are ignored. If the control block referenced
by aiocbp becomes an illegal address prior to asynchronous I/O completion, then the behav-
ior is undefined.
If the aio_fsync() function fails or aiocbp indicates an error condition, data is not
guaranteed to have been successfully transferred.
The aio_fsync() function shall return the value 0 to the calling process if the I/O opera-
tion is successfully queued; otherwise, the function shall return the value -1 and set
errno to indicate the error.
The aio_fsync() function shall fail if:
EAGAIN The requested asynchronous operation was not queued due to temporary resource limi-
EBADF The aio_fildes member of the aiocb structure referenced by the aiocbp argument is
not a valid file descriptor open for writing.
EINVAL This implementation does not support synchronized I/O for this file.
EINVAL A value of op other than O_DSYNC or O_SYNC was specified.
In the event that any of the queued I/O operations fail, aio_fsync() shall return the
error condition defined for read() and write(). The error is returned in the error status
for the asynchronous fsync() operation, which can be retrieved using aio_error().
The following sections are informative.
The aio_fsync() function is part of the Asynchronous Input and Output option and need not
be available on all implementations.
fcntl() , fdatasync() , fsync() , open() , read() , write() , the Base Definitions volume
of IEEE Std 1003.1-2001, <aio.h>
Portions of this text are reprinted and reproduced in electronic form from IEEE Std
1003.1, 2003 Edition, Standard for Information Technology -- Portable Operating System
Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by
the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the
event of any discrepancy between this version and the original IEEE and The Open Group
Standard, the original IEEE and The Open Group Standard is the referee document. The orig-
inal Standard can be obtained online at http://www.opengroup.org/unix/online.html .
IEEE/The Open Group 2003 AIO_FSYNC(P)