How does behave linux buffer cache when an application is crashing down?

Question

Let\'s say I am using c++ files stream asynchronously. I mean never using std::flush nor std::endl. My application writes a lot of data to a file and abruptly crashes down.

Answer 1

The stuff in the library buffer (which you flush with std::flush or such) is lost, the data in the OS kernel buffers (which you can flush e.g. with fsync()) is not lost unless the OS itself crashes.