Hello Guile users, I am trying to find a way to read a character from command line or REPL, without having to enter a newline, confirming the input. For example I found this for Python: https://stackoverflow.com/a/21659588 <https://stackoverflow.com/a/21659588> I read on https://www.gnu.org/software/guile/manual/html_node/Buffering.html <https://www.gnu.org/software/guile/manual/html_node/Buffering.html> about buffering and thought, that I could simply set the port to be unbuffered using (setvbuf port 'none) and then call (get-char port) as follows: ~~~~ (import (except (rnrs base) let-values map) (only (guile) ;; lambda forms lambda* λ ;; input output current-input-port) (ice-9 textual-ports) (ice-9 optargs)) (let ([port (current-input-port)]) (setvbuf port 'none) (get-char port)) ~~~~ However, this does not work. The terminal emulator might not send input immediately to the Guile program. Even in the Guile REPL and in Emacs Geiser this does not work. I guess it would work, if they did send each character immediately to the Guile program, because the following works: ~~~~ (display (call-with-input-string "ab" (λ (in-port) (setvbuf in-port 'none) (get-char in-port)))) ~~~~ There is no newline in the string "ab" and only the "a" is displayed. So the question might be, how one can get into a mode, where Guile receives input immediately, taking over control of the terminal or REPL. However, I am not sure how the Python solution does this. I have some command line program, in which I let the user choose what to do next by entering a character and then pressing the return key to confirm the input. I think it would be nice to not have to press return all the time and only needing to press the character's key. Does anyone know how to do this in Guile? Best regards, Zelphir -- repositories: https://notabug.org/ZelphirKaltstahl
On Sat, Aug 28, 2021 at 02:09:52PM +0000, Zelphir Kaltstahl wrote:
> Hello Guile users,
>
> I am trying to find a way to read a character from command line or REPL, without
> having to enter a newline, confirming the input.
>
> For example I found this for Python: https://stackoverflow.com/a/21659588
> <https://stackoverflow.com/a/21659588>
>
> I read on https://www.gnu.org/software/guile/manual/html_node/Buffering.html
> <https://www.gnu.org/software/guile/manual/html_node/Buffering.html> about
> buffering and thought, that I could simply set the port to be unbuffered using
> (setvbuf port 'none) and then call (get-char port) as follows:
>
> ~~~~
> (import
> (except (rnrs base) let-values map)
> (only (guile)
> ;; lambda forms
> lambda* ??
> ;; input output
> current-input-port)
> (ice-9 textual-ports)
> (ice-9 optargs))
>
> (let ([port (current-input-port)])
> (setvbuf port 'none)
> (get-char port))
> ~~~~
>
> However, this does not work. The terminal emulator might not send input
> immediately to the Guile program. Even in the Guile REPL and in Emacs Geiser
> this does not work. I guess it would work, if they did send each character
> immediately to the Guile program, because the following works:
>
> ~~~~
> (display
> (call-with-input-string "ab"
> (?? (in-port)
> (setvbuf in-port 'none)
> (get-char in-port))))
> ~~~~
>
> There is no newline in the string "ab" and only the "a" is displayed.
>
> So the question might be, how one can get into a mode, where Guile receives
> input immediately, taking over control of the terminal or REPL.
Hello. For this to work, your terminal needs to be in 'raw' mode
where it sends characters immediately. Terminals are normally
in 'cooked' mode where it waits for a return before it sends everything.
The simple way to get into raw mode would be to run your script like
stty raw && guile script.scm
But if you want to get the terminal into raw mode from within guile,
you need to get guile to call a function like 'tcsetattr' to set the
mode of your terminal. Or maybe just call the stty program from within
guile?
There is a binding of tcsetattr in the (ncurses extra) library
in guile-ncurses, but since you just need a couple of functions, you
could wrap them in FFI, I suppose.
-Mike
On Sat, 28 Aug 2021 14:09:52 +0000 Zelphir Kaltstahl <zelphirkaltstahl@posteo.de> wrote: > Hello Guile users, > > I am trying to find a way to read a character from command line or REPL, without > having to enter a newline, confirming the input. > > For example I found this for Python: https://stackoverflow.com/a/21659588 > <https://stackoverflow.com/a/21659588> > > I read on https://www.gnu.org/software/guile/manual/html_node/Buffering.html > <https://www.gnu.org/software/guile/manual/html_node/Buffering.html> about > buffering and thought, that I could simply set the port to be unbuffered using > (setvbuf port 'none) and then call (get-char port) as follows: > > ~~~~ > (import > (except (rnrs base) let-values map) > (only (guile) > ;; lambda forms > lambda* λ > ;; input output > current-input-port) > (ice-9 textual-ports) > (ice-9 optargs)) > > (let ([port (current-input-port)]) > (setvbuf port 'none) > (get-char port)) > ~~~~ > > However, this does not work. The terminal emulator might not send input > immediately to the Guile program. Even in the Guile REPL and in Emacs Geiser > this does not work. I guess it would work, if they did send each character > immediately to the Guile program, because the following works: > > ~~~~ > (display > (call-with-input-string "ab" > (λ (in-port) > (setvbuf in-port 'none) > (get-char in-port)))) > ~~~~ > > There is no newline in the string "ab" and only the "a" is displayed. > > So the question might be, how one can get into a mode, where Guile receives > input immediately, taking over control of the terminal or REPL. > > However, I am not sure how the Python solution does this. > > I have some command line program, in which I let the user choose what to do next > by entering a character and then pressing the return key to confirm the input. I > think it would be nice to not have to press return all the time and only needing > to press the character's key. > > Does anyone know how to do this in Guile? It's not guile doing the buffering, it's your terminal. By default your terminal is in canonical (aka "cooked") mode. This means amongst other things that input is not delivered from the keyboard on /dev/tty until a new line is entered. On unix-like operating systems you can change to non-canonical mode and set other terminal parameters using termios, or if you don't want to write some C you can just call up stty using system*. (system* "stty" "--file=/dev/tty" "cbreak") will probably do what you want, but you will then probably want to restore cooked mode when your program exits. This may also help you: https://en.wikibooks.org/wiki/Serial_Programming/termios
Mike Gran wrote: […] > There is a binding of tcsetattr in the (ncurses extra) library > in guile-ncurses, but since you just need a couple of functions, you > could wrap them in FFI, I suppose. Shameless plug: https://gitlab.com/ft/guile-termios I sort of have this ready for guix, too. But I never got around to actu- ally submitting it. Regards, Frank -- In protocol design, perfection has been reached not when there is nothing left to add, but when there is nothing left to take away. -- RFC 1925
Second for guile-termios, I use it and like it very much (saved my bacon
with a program I was writing).
On Sat, Aug 28, 2021 at 3:56 PM Frank Terbeck <ft@bewatermyfriend.org>
wrote:
> Mike Gran wrote:
> […]
> > There is a binding of tcsetattr in the (ncurses extra) library
> > in guile-ncurses, but since you just need a couple of functions, you
> > could wrap them in FFI, I suppose.
>
> Shameless plug: https://gitlab.com/ft/guile-termios
>
> I sort of have this ready for guix, too. But I never got around to actu-
> ally submitting it.
>
>
> Regards, Frank
> --
> In protocol design, perfection has been reached not when there is
> nothing left to add, but when there is nothing left to take away.
> -- RFC 1925
>
>
Thank you all for your pointers, hints and solutions!
I shall try them out : )
Best regards,
Zelphir
On 8/29/21 1:47 AM, Tim Meehan wrote:
> Second for guile-termios, I use it and like it very much (saved my bacon
> with a program I was writing).
>
> On Sat, Aug 28, 2021 at 3:56 PM Frank Terbeck <ft@bewatermyfriend.org>
> wrote:
>
>> Mike Gran wrote:
>> […]
>>> There is a binding of tcsetattr in the (ncurses extra) library
>>> in guile-ncurses, but since you just need a couple of functions, you
>>> could wrap them in FFI, I suppose.
>> Shameless plug: https://gitlab.com/ft/guile-termios
>>
>> I sort of have this ready for guix, too. But I never got around to actu-
>> ally submitting it.
>>
>>
>> Regards, Frank
>> --
>> In protocol design, perfection has been reached not when there is
>> nothing left to add, but when there is nothing left to take away.
>> -- RFC 1925
>>
>>