fdatasync - synchronize a file's in-core data with that on
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
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 set appropriately.
EBADF fd is not a valid file descriptor open for writing.
fd is bound to a special file which does not sup
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