if (no_tty_flag)
tty_flag = 0;
/* Do not allocate a tty if stdin is not a tty. */
if (!isatty(fileno(stdin)) && !force_tty_flag) {
if ((!isatty(fileno(stdin)) || stdin_null_flag) && !force_tty_flag) {
if (tty_flag)
logit("Pseudo-terminal will not be allocated because stdin is not a terminal.");