FDATASYNC(2) Linux Programmer's Manual FDATASYNC(2)NAMEfdatasync - synchronize a file's in-core data with that on disk
int fdatasync(int fd);
DESCRIPTIONfdatasync() flushes all data buffers of a file to disk (before the sys‐
tem 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() immedi‐
ately 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 synchro‐
Currently (Linux 2.2) fdatasync() is equivalent to fsync().
On POSIX systems on which fdatasync() is available, _POSIX_SYNCHRO‐
NIZED_IO is defined in <unistd.h> to a value greater than 0. (See also
B.O. Gallmeister, POSIX.4, O'Reilly, pp. 220-223 and 343.
Linux 1.3.86 1996-04-13 FDATASYNC(2)