MAN page from Old RedHat 5.X man-pages-1.19-1.noarch.rpm

FDATASYNC

Section: Linux Programmer's Manual (2)
Updated: 13 April 1996
Index

NAME

fdatasync - synchronize a file's in-core data with that on disk

SYNOPSIS

#include <unistd.h>

#ifdef _POSIX_SYNCHRONIZED_IO

int fdatasync(int fd);

#endif

DESCRIPTION

fdatasyncflushes all data buffers of a file to disk (before the systemcall returns). It resemblesfsyncbut is not required to update the metadata such as access time.

Applications that access databases or log files often write a tinydata fragment (e.g., one line in a log file) and then callfsyncimmediately in order to ensure that the written data is physicallystored on the harddisk. Unfortunately,fsyncwill always initiate two write operations: one for the newly writtendata and another one in order to update the modification time storedin the inode. If the modification time is not a part of the transactionconceptfdatasynccan be used to avoid unnecessary inode disk write operations.

RETURN VALUE

On success, zero is returned. On error, -1 is returned, anderrnois set appropriately.

ERRORS

EBADF: fdis not a valid file descriptor open for writing.
EROFS, EINVAL: fdis bound to a special file which does not support synchronization.
EIO: An error occurred during synchronization.

BUGS

Currently (Linux 2.0.23)fdatasyncis equivalent tofsync.

CONFORMING TO

POSIX1b (formerly POSIX.4)

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