xwrite
(void) xwrite(fileno(stdout), rbuf, amt);
if (xwrite(rem_w, buf, (size_t) amt) < 0) {
return(!(xwrite(rem_w, msg, len) == len));
(void) xwrite(rem_w, sbuf, s - sbuf);
(void) xwrite(rem_w, sbuf, s - sbuf);
ssize_t xwrite(int, void *, size_t);
if (wrerr == 0 && xwrite(f, buf, amt) != amt) {