(require :sb-posix)
(import '(sb-posix:termios sb-posix:termios-lflag sb-posix:termios-cc
sb-posix:tcgetattr sb-posix:tcsetattr
sb-posix:tcsadrain
sb-posix:icanon sb-posix:echo sb-posix:echoe sb-posix:echok
sb-posix:echonl sb-posix:vmin sb-posix:vtime))

#| What "less" does:
s.c_lflag &= ~(ICANON|ECHO|ECHOE|ECHOK|ECHONL);
s.c_oflag |= (OPOST|ONLCR|TAB3);
s.c_oflag &= ~(OCRNL|ONOCR|ONLRET);
s.c_cc[VMIN] = 1;
s.c_cc[VTIME] = 0;
|#
(defun read-char-no-echo-cbreak (&optional (stream *query-io*))
(let ((old (tcgetattr 0))
(new (tcgetattr 0))
(bits (logior icanon echo echoe echok echonl)))
(unwind-protect
(progn
(setf (termios-lflag new) (logandc2 (termios-lflag old) bits)
(aref (termios-cc new) vmin) 1
(aref (termios-cc new) vtime) 0)
(tcsetattr 0 tcsadrain new)
(read-char stream))
(tcsetattr 0 tcsadrain old))))