prep_io          5819 io.c               return prep_io(fd, rb_io_oflags_fmode(oflags), klass, path);
prep_io          5826 io.c               VALUE io = prep_io(fileno(f), fmode|FMODE_PREP, klass, path);
prep_io          6231 io.c           		    rb_stdout = prep_io(fw, FMODE_WRITABLE, rb_cFile, fn);
prep_io          6234 io.c           		ARGF.current_file = prep_io(fr, FMODE_READABLE, rb_cFile, fn);