pty_write_to_fd
static int pty_write_to_fd(int fd, const char *string, int n);
if(pty_write_to_fd(cntrl, line, strlen(line)))
(void) pty_write_to_fd(STDOUT_FILENO, "\r", 1);
(void) pty_write_to_fd(STDOUT_FILENO, rbuff, nextp - rbuff);
(void) pty_write_to_fd(STDOUT_FILENO, "\r\n", 2);