Section: POSIX Programmer's Manual (3P)
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.
--- synchronize the data of a file
int fdatasync(int fildes);
function shall force all currently queued I/O operations associated
with the file indicated by file descriptor
to the synchronized I/O completion state.
The functionality shall be equivalent to
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 integrity completion.
If successful, the
function shall return the value 0; otherwise, the function shall return
the value -1 and set
to indicate the error. If the
function fails, outstanding I/O operations are not guaranteed to have
function shall fail if:
argument is not a valid file descriptor open for writing.
This implementation does not support synchronized I/O for this file.
In the event that any of the queued I/O operations fail,
shall return the error conditions defined for
The following sections are informative.
The Base Definitions volume of POSIX.1-2008,
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
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