Originální popis anglicky:
fdatasync - synchronize a file's in-core data with that on disk
Návod, kniha: Linux Programmer's Manual
#include <unistd.h>
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 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.
- EIO
- An error occurred during synchronization.
- EROFS, EINVAL
- fd is bound to a special file which does not support
synchronization.
Currently (Linux 2.2)
fdatasync is equivalent to
fsync.
On POSIX systems on which
fdatasync is available,
_POSIX_SYNCHRONIZED_IO is defined in <unistd.h> to a value
greater than 0. (See also
sysconf(3).)
POSIX1b (formerly POSIX.4)
fsync(2)
B.O. Gallmeister, POSIX.4, O'Reilly, pp. 220-223 and 343.
