Linux man pages : fdatasync (2)
FDATASYNC(2) Linux Programmer's Manual FDATASYNC(2)
fdatasync - synchronize a file's in-core data with that on disk
int fdatasync(int fd);
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.
On success, zero is returned. On error, -1 is returned, and errno is
EBADF fd is not a valid file descriptor open for writing.
fd is bound to a special file which does not support synchro-
EIO An error occurred during synchronization.
Currently (Linux 2.2) fdatasync is equivalent to fsync.
POSIX1b (formerly POSIX.4)
fsync(2), B.O. Gallmeister, POSIX.4, O'Reilly, pp. 220-223 and 343.
Linux 1.3.86 1996-04-13 FDATASYNC(2)