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FDATASYNC(2) Linux Programmer's Manual FDATASYNC(2)
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 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)
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