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FDATASYNC(2)		   Linux Programmer's Manual		  FDATASYNC(2)

NAME
       fdatasync - synchronize a file's in-core data with that on disk

SYNOPSIS
       #include <unistd.h>

       int fdatasync(int fd);

DESCRIPTION
       fdatasync() flushes all data buffers of a file to disk (before the sys-
       tem call returns).  It resembles fsync() but is not required to	update
       the metadata such as access time.

       Applications that access databases or log files often write a tiny data
       fragment (e.g., one line in a log file) and then call  fsync()  immedi-
       ately  in order to ensure that the written data is physically stored on
       the harddisk. Unfortunately, fsync() will  always  initiate  two	 write
       operations:  one for the newly written data and another one in order to
       update the modification time stored in the inode. If  the  modification
       time  is	 not a part of the transaction concept fdatasync() can be used
       to avoid unnecessary inode disk write operations.

RETURN VALUE
       On success, zero is returned.  On error, -1 is returned, and  errno  is
       set appropriately.

ERRORS
       EBADF  fd is not a valid file descriptor open for writing.

       EIO    An error occurred during synchronization.

       EROFS, EINVAL
	      fd  is  bound  to a special file which does not support synchro-
	      nization.

BUGS
       Currently (Linux 2.2) fdatasync() is equivalent to fsync().

AVAILABILITY
       On POSIX systems on which  fdatasync()  is  available,  _POSIX_SYNCHRO-
       NIZED_IO	 is defined in <unistd.h> to a value greater than 0. (See also
       sysconf(3).)

CONFORMING TO
       POSIX.1-2001.

SEE ALSO
       fsync(2) sync_file_range(2),
       B.O. Gallmeister, POSIX.4, O'Reilly, pp. 220-223 and 343.

Linux 1.3.86			  1996-04-13			  FDATASYNC(2)