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
intfdatasync(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 immediately
in order to ensure that the written data is physically stored on the
harddisk. Unfortunately, fsync will always initiate two write opera-
tions: 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.
RETURNVALUE
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 synchro-
nization.
EIO An error occurred during synchronization.
BUGS
Currently (Linux 2.2) fdatasync is equivalent to fsync.
CONFORMINGTO
POSIX1b (formerly POSIX.4)
SEEALSO
fsync(2), B.O. Gallmeister, POSIX.4, O'Reilly, pp. 220-223 and 343.
Linux 1.3.86 1996-04-13 FDATASYNC(2)
Take our 
