This manual page is part of the POSIX Programmer's Manual. The Linux
implementation of this interface may differ (consult the
corresponding Linux manual page for details of Linux behavior), or
the interface may not be implemented on Linux.
The aio_fsync() function shall asynchronously perform a file
synchronization operation, as specified by the op argument, for 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(). 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 synchronized immediately).
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
outstanding I/O operations are not guaranteed to have been completed.
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 completion 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 member determines the
asynchronous notification to occur as specified in Section 2.4.1,
Signal Generation and Delivery when all operations have achieved
synchronized I/O completion. All other members 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 behavior is undefined.
If the aio_fsync() function fails or aiocbp indicates an error
condition, data is not guaranteed to have been successfully
The aio_fsync() function shall fail if:
EAGAIN The requested asynchronous operation was not queued due to
temporary resource limitations.
EBADF The aio_fildes member of the aiocb structure referenced by the
aiocbp argument is not a valid file descriptor open for
EINVAL This implementation does not support synchronized I/O for this
EINVAL The aio_fildes member of the aiocb structure refers to a file
on which an fsync() operation is not possible.
EINVAL A value of op other than O_DSYNC or O_SYNC was specified, or
O_DSYNC was specified and the implementation does not provide
runtime support for the Synchronized Input and Output option,
or O_SYNC was specified and the implementation does not
provide runtime support for the File Synchronization option.
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 operation,
which can be retrieved using aio_error().
The following sections are informative.
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information
Technology -- Portable Operating System Interface (POSIX), The Open
Group Base Specifications Issue 7, Copyright (C) 2013 by the
Institute of Electrical and Electronics Engineers, Inc and The Open
Group. (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1
applied.) 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 original
Standard can be obtained online at http://www.unix.org/online.html .
Any typographical or formatting errors that appear in this page are
most likely to have been introduced during the conversion of the
source files to man page format. To report such errors, see
IEEE/The Open Group 2013 AIO_FSYNC(3P)