Re: Reading characters from stdin

[Matthew Wild <mwild1@...>]

On 21 September 2012 15:34, Rena <hyperhacker@gmail.com> wrote:
> (Yep, this question again. :p)
>
> I'm coding in a rather limited Linux-like environment: I have a text editor,
> a terminal emulator, a Lua 5.1 interpreter, and not much else. I don't have
> a C compiler.
>
> My problem is I want to read keys from stdin as soon as they're pressed,
> without having to press enter. The only ways I know to do this involve C
> function calls. Is there perhaps an ANSI escape code or some other crazy
> trick I can use? Can I call some program with os.execute to change terminal
> settings?

Try this small function:

    function getchar(n)
        local stty_ret = os.execute("stty raw 2>/dev/null");
        local ok, char;
        if stty_ret == 0 then
            ok, char = pcall(io.read, n or 1);
            os.execute("stty sane");
        else
            ok, char = pcall(io.read, "*l");
            if ok then
                char = char:sub(1, n or 1);
            end
        end
        if ok then
            return char;
        end
    end

An improvement would be to save the current stty settings, and then
restore them (instead of 'stty sane'). I don't know how "portable"
this is though.

Hope this helps,
Matthew

PS. The code is taken from Prosody, which is MIT licensed.