How to use getch() in a loop (nCurses)

Question

This is my first time using ncurses library. So, I wanted to use getch() to get a character as it is typed by the user (without pressing return every time). However, when I run this code:

#include <pthread.h>
#include <stdio.h>
#include <curses.h>

void *userInput() {
char c;

while((c = getch()) != '~') {
    printf("%c\n",c);
}

pthread_exit(NULL);

}

int main() {
    cbreak();

    pthread_t threads[4];

    pthread_create(&threads[0], NULL, userInput, NULL);

    pthread_exit(NULL);
}

It printf lots of '?'s without getting any input. Could anyone please help me understand whats wrong? Thank you.

EDIT: removed dead code.

Possible duplicate of [Why getch() returns before press any key?](https://stackoverflow.com/questions/7410447/why-getch-returns-before-press-any-key) — KevinDTimm, Jun 07 '17 at 19:43
Well, you don't have any `WINDOW *`, not even the `stdscr` which is created by `initscr()` (`getch()` implicitly works on `stdscr`). I'm not sure, but I could well imagine that this is the source of your problem: `getch()` is intended to be used as long as `stdscr` exists. — , Jun 07 '17 at 20:57

score 0 · Answer 1 · answered Jun 08 '17 at 00:57

There are at least three problems with the program:

getch will always return an error because you did not initialize the screen with initscr or newterm. Likewise, the cbreak call does nothing except return an error.
even if you initialized the screen, calling getch with multiple threads will not work predictably because it is not thread-safe. It's an FAQ: Why does (fill in the blank) happen when I use two threads?
the printf does something, but mixing stdio (printf) and curses does not work as you'd like. Use printw for curses applications.

As for printing ?, those -1's sent to a terminal which expects UTF-8 would likely decide they're not valid UTF-8 and display the replacement character.

How to use getch() in a loop (nCurses)

1 Answers1