Why does the `reset` command include a delay?

Question

The reset command includes a delay, between clearing the screen and returning. This is even on the latest terminal type xterm-256color. Why?

man reset does not mention a delay, only the printing of special strings. (It doesn't mention clearing the screen either. I assume this is included under the terminal initialization string).

I notice the follow output in strace -f reset:

nanosleep({tv_sec=1, tv_nsec=0}, 0x7ffe1964f100) = 0
ioctl(2, SNDCTL_TMR_STOP or TCSETSW, {B38400 opost isig icanon echo ...}) = 0

Answer 1

Real (hardware) terminals need that. For instance, with some, the only way to reset them is to do a hardware-reset.

It's harmless with a terminal emulator, and since there's no conventional way to tell the difference (and too hard to determine if some escape sequence might do a hardware-reset), reset assumes your terminal is real.

The time-delay dates back to tset in 3BSD in 1979, like this:

    /* output startup string */
    if (!RepOnly && !NoInit)
    {
            bufp = buf;
            if (tgetstr("is", &bufp) != 0)
                    prs(buf);
            bufp = buf;
            if (tgetstr("if", &bufp) != 0)
                    cat(buf);
            sleep(1);       /* let terminal settle down */
    }

It's evolved somewhat in ncurses, but using the same guideline:

        if (!noinit) {
            if (send_init_strings(my_fd, &oldmode)) {
                (void) putc('\r', stderr);
                (void) fflush(stderr);
                (void) napms(1000);         /* Settle the terminal. */
            }
        }

Further reading:

• History (tset manual page)
• History (tput manual page)

Answer 2

Note that as of release 6.5 of ncurses (April 27, 2024), the one-second delay has been removed in most cases.

See the release note:

tput and tset

• add “-v” option to tput, to show warnings
• modify reset command to avoid altering clocal if the terminal uses a modem
• modify reset feature to avoid 1-second sleep if running in a pseudo-terminal

Using reset in a terminal with an updated package is now basically instantaneous.