Problems with POSIX I/O and buffering
From John Donners:
I've also experimented a lot with the POSIX interface and the internal buffering for SIONlib. The SIONlib buffer seems not flushed at the moment that the file is closed. I've added an extra routine to flush the buffer, which uses the same code as in sion_fwrite. I'm not sure where to insert the code in the different SIONlib close calls.