The f_sync function flushes the cached information of a writing file.
FRESULT f_sync ( FIL* fp /* [IN] File object */ );
FR_OK, FR_DISK_ERR, FR_INT_ERR, FR_INVALID_OBJECT, FR_TIMEOUT
The f_sync function performs the same process as f_close function but the file is left opened and can continue read/write/seek operations to the file. This is suitable for the applications that open files for a long time in write mode, such as data logger. Performing f_sync function of periodic or immediataly after f_write function can minimize the risk of data loss due to a sudden blackout or an unintentional media removal. For more information, refer to application note.
However there is no sense in f_sync function immediataly before f_close function because it performs f_sync function in it. In other words, the differnce between those functions is that the file object is invalidated or not.
Available when _FS_READONLY == 0.