fdatasync - synchronize a file's in-core data with that on disk
#include <unistd.h>
#ifdef _POSIX_SYNCHRONIZED_IO
int fdatasync(int fd);
#endif
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 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.
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.
EROFS, EINVAL
fd is bound to a special file which does not support synchronization.
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)
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