'\" et
.TH FDATASYNC "3P" 2017 "IEEE/The Open Group" "POSIX Programmer's Manual"
.\"
.SH PROLOG
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.
.\"
.SH NAME
fdatasync
\(em synchronize the data of a file
(\fBREALTIME\fP)
.SH SYNOPSIS
.LP
.nf
#include <unistd.h>
.P
int fdatasync(int \fIfildes\fP);
.fi
.SH DESCRIPTION
The
\fIfdatasync\fR()
function shall force all currently queued I/O operations associated
with the file indicated by file descriptor
.IR fildes
to the synchronized I/O completion state.
.P
The functionality shall be equivalent to
\fIfsync\fR()
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.
.SH "RETURN VALUE"
If successful, the
\fIfdatasync\fR()
function shall return the value 0; otherwise, the function shall return
the value \-1 and set
.IR errno
to indicate the error. If the
\fIfdatasync\fR()
function fails, outstanding I/O operations are not guaranteed to have
been completed.
.SH ERRORS
The
\fIfdatasync\fR()
function shall fail if:
.TP
.BR EBADF
The
.IR fildes
argument is not a valid file descriptor.
.TP
.BR EINVAL
This implementation does not support synchronized I/O for this file.
.P
In the event that any of the queued I/O operations fail,
\fIfdatasync\fR()
shall return the error conditions defined for
\fIread\fR()
and
\fIwrite\fR().
.LP
.IR "The following sections are informative."
.SH EXAMPLES
None.
.SH "APPLICATION USAGE"
Note that even if the file descriptor is not open for writing,
if there are any pending write requests on the underlying file,
then that I/O will be completed prior to the return of
\fIfdatasync\fR().
.SH RATIONALE
None.
.SH "FUTURE DIRECTIONS"
None.
.SH "SEE ALSO"
.IR "\fIaio_fsync\fR\^(\|)",
.IR "\fIfcntl\fR\^(\|)",
.IR "\fIfsync\fR\^(\|)",
.IR "\fIopen\fR\^(\|)",
.IR "\fIread\fR\^(\|)",
.IR "\fIwrite\fR\^(\|)"
.P
The Base Definitions volume of POSIX.1\(hy2017,
.IR "\fB<unistd.h>\fP"
.\"
.SH COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1-2017, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, 2018 Edition,
Copyright (C) 2018 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
http://www.opengroup.org/unix/online.html .
.PP
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
https://www.kernel.org/doc/man-pages/reporting_bugs.html .