ttwrite
error = ttwrite(tp, &uio2, flag);
{ ttyopen, ttylclose, ttread, ttwrite,
int ttwrite (struct tty *tp, struct uio *uio, int flag);
ttwrite(p->string, p->length);
void ttwrite(const char *, int);
#define ttxputs(s) ttwrite((s)->ts_str, (s)->ts_n)
ttwrite(p, n);
ttwrite(p, n);
ttwrite(p, n);
ttwrite(s, n);