Write file without system cache and hdd

Question

How can I write something to a file in C ++ without using the system cache and disk cache? I just want to write exactly on hdd, regardless of all the system cache settings.

Answer 1

If you are not writing a disk device driver, you cannot guarantee that there will be no cache or processing with your record.

The C time library provides fflush(FILE *)for this. Windows has FlushFileBuffers, as well as a flag that you can pass in CreateFile( FILE_FLAG_NO_BUFFERING) (which itself adds restrictions on what you can do).

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Answer 2

. Windows FILE_FLAG_NO_BUFFERING, CreateFile, . .

Answer 3

On Linux, you can pass O_DIRECTin open(2)to try to avoid the OS cache, but you do not have the same level of control over the disk cache.