The fdatasync() function shall force all currently queued I/O
operations associated with the file indicated by file
descriptor fildes to the synchronized I/O completion state.
The functionality shall be equivalent to fsync() with the symbol
_POSIX_SYNCHRONIZED_IO defined, with the exception that all I/O operations
shall be completed as defined for synchronized I/O data
If successful, the fdatasync() function shall return the value
0; otherwise, the function shall return the value -1 and
set errno to indicate the error. If the fdatasync() function
fails, outstanding I/O operations are not guaranteed to
have been completed.
The fdatasync() function shall fail if:
The fildes argument is not a valid file descriptor open for
This implementation does not support synchronized I/O for this file.
In the event that any of the queued I/O operations fail, fdatasync()
shall return the error conditions defined for read() and write().
The following sections are informative.
aio_fsync() , fcntl() , fsync() , open() ,
read() , write() , the Base Definitions volume of IEEE Std 1003.1-2001,
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 original Standard can be obtained online at