c++ std::ofstream flush() but not close()

c++ flush buffering ofstream
anon picture anon · Feb 26, 2010 · Viewed 8k times · Source

I'm on MacOSX.

In the logger part of my application, I'm dumping data to a file.

suppose I have a globally declared std::ofstream outFile("log");

and in my logging code I have:

outFile << "......." ;
outFile.flush();

Now, suppose my code crashes after the flush() happens; Is the stuff written to outFile before the flush() guaranteed to be written to disk (note that I don't call a close()).

Thanks!

Answer

Timo Geusch picture Timo Geusch · Feb 26, 2010

From the C++ runtime's point of view, it should have been written to disk. From an OS perspective it might still linger in a buffer, but that's only going to be an issue if your whole machine crashes.

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