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>

       #ifdef _POSIX_SYNCHRONIZED_IO

       int fdatasync(int fd);

       #endif

DESCRIPTION

       fdatasync  flushes  all	data buffers of a file to disk (before the system 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  modifica-
       tion 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.

       EROFS, EINVAL
	      fd is bound to a special file which does not support synchronization.

       EIO    An error occurred during synchronization.

BUGS

       Currently (Linux 2.2) fdatasync is equivalent to fsync.

CONFORMING TO

       POSIX1b (formerly POSIX.4)

SEE ALSO

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

Linux 1.3.86							    1996-04-13							      FDATASYNC(2)