If you're talking about fflush() from the C standard libray, fflush() doesn't write to disk. It pushes writes from the FILE's buffer to the kernel and drops an

If you're talking about fflush() from the C standard libray, fflush() doesn't write to disk. It pushes writes from the FILE's buffer to the kernel and drops any read data that has been cached. The C standard library doesn't really provide you with all the tools needed to commit writes to disk fully.