Execute function more than once while key is pressed (ncurses)

Question

I would like to be able to run the function execlp(...) more than once when pressing the right key (this works only on mac, it basically uses oasascript to press the corresponding key for increasing the brightness as I know these special keys can't be simulated with ncurses).

The program compiles and runs, but when I press the right key, it increases the brightness once then interrupts. I would like to keep it running so when the right key is pressed again to repeat the action while the key is kept pressed.

#include <ncurses.h>
#include <unistd.h>
#include <stdio.h>

int main(int argc, char *argv[]) {
  int key = 0;

  initscr();
  noecho();
  curs_set(TRUE);
  keypad(stdscr, TRUE);
  nodelay(stdscr, TRUE);

  while(1) {
    clear();

    refresh();
    key = getch();

    if (key == KEY_RIGHT) {
      execlp(
        "osascript",
        "osascript",
        "-e",
        "tell application \"System Events\" to key code 144 using {option down, shift down}",
        NULL
      );
    }
  }
  endwin();
}

`execlp` will replace current process with newly executed command, so you will have to use `fork()` to create new process for running new command. — MikeCAT, Dec 27 '20 at 15:31
@ryyker on mac, I have specified in the description. `oascript` is a osx specific command — skamsie, Dec 27 '20 at 20:05
So you did, sorry. Missed that. I found [this about that](https://stackoverflow.com/a/16283140) — ryyker, Dec 27 '20 at 20:10

score 0 · Answer 1 · answered Dec 28 '20 at 15:05

0

By its nature, you can't run execlp() more than once, but you can replace it with fork() or the like. But my preference would be to look for a direct API solution to control the brightness, rather than launching a separate process to fake a keypress. To that end, I found this: Adjust screen brightness in Mac OS X app

answered Dec 28 '20 at 15:05

William McBrine

2,166
11
7

Thanks, but you are pointing to a `swift` solution and I am intersted in a `C` implementation. There is already a nice low level implementation for in `C` as well here: https://github.com/nriley/brightness, but this has the caveat of not updating the brightness slider to the value you are setting via the app. Anyway, in my case I have solved it by using `system()` instead of `execlp()` – skamsie Dec 28 '20 at 17:08

Execute function more than once while key is pressed (ncurses)

1 Answers1