Provided by: manpages-dev_2.17-1_all
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 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
EBADF fd is not a valid file descriptor open for writing.
EIO An error occurred during synchronization.
fd is bound to a special file which does not support
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)
B.O. Gallmeister, POSIX.4, O’Reilly, pp. 220-223 and 343.