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.

NAME

       fdatasync — synchronize the data of a file (REALTIME)

SYNOPSIS

       #include <unistd.h>

       int fdatasync(int fildes);

DESCRIPTION

       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 integrity completion.

RETURN VALUE

       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.

ERRORS

       The fdatasync() function shall fail if:

       EBADF  The fildes argument is not a valid file descriptor.

       EINVAL 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.

EXAMPLES

       None.

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 fdatasync().

RATIONALE

       None.

FUTURE DIRECTIONS

       None.

SEE ALSO

       aio_fsync(), fcntl(), fsync(), open(), read(), write()

       The Base Definitions volume of POSIX.1‐2017, <unistd.h>

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 .

       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 .