How to define a certain time for the getch() function in C?

Question

I am trying to have the function getch() of the C language in Windows to work only for a few seconds.

#include <stdio.h>
#include <windows.h>
int main()
{
    int v1, v2;
    v1=getch();//I want this getch to only be activated for a few seconds
    printf("Example");//That to activate the next function, even if the person reading this programm doesn't click in any key
    return 0;
}

Can you make `stdin` unbuffered? https://stackoverflow.com/questions/10247591/setvbuf-not-able-to-make-stdin-unbuffered — Fiddling Bits, Feb 17 '20 at 20:05
Windows - you can check `kbhit()` in a timeout loop - say using `clock()`. No special steps are needed, it is provided for you so you don't have to commit to the blocking function — Weather Vane, Feb 17 '20 at 20:12
@MarcoBonelli I wasn't clear. What I meant was you can spin in a loop and `break` when time has expired. The problem with `getch` (`stdin`) is that it blocks by default, right? — Fiddling Bits, Feb 17 '20 at 20:13
@FiddlingBits exactly, it's not "by default", it just blocks if there's no data available, that's it. — Marco Bonelli, Feb 17 '20 at 20:15
@FiddlingBits `getch` isn't `stdin`. It can't be redirected. — Weather Vane, Feb 17 '20 at 20:19
The answer is no, you cannot timeout a call to getch(). You have to think of a different way to attain your goal. — john elemans, Feb 17 '20 at 20:57

score 0 · Answer 1 · answered Feb 17 '20 at 20:59

0

you need to use the ncurse library and call:

initscr or newterm to initialize the screen
timeout with a positive delay. Otherwise, it will not be blocking.

Read more here

answered Feb 17 '20 at 20:59

melissanais

74
6

score 0 · Answer 2 · answered Feb 17 '20 at 21:14

You can use kbhit() which tests if a key has been pressed, before committing to the blocking function getch(). The loop below uses clock() to check for timeout.

#include <conio.h>
#include <stdio.h>
#include <ctype.h>
#include <time.h>

#define TIMEOUT 5   // seconds

int main(void)
{
    clock_t tstart = clock();
    int v1 = 'y';                   // default key press
    while((clock() - tstart) / CLOCKS_PER_SEC < TIMEOUT) {
        if(kbhit()) {
            v1 = getch();
            break;
        }
    }
    if(tolower(v1) == 'y')
        printf("Example\n");
    return 0;
}

It's particularly useful in a game, where you don't want to sit there waiting for a key press, and then it isn't quite so simple to use. When you press a function key or a cursor key getch() returns two successive characters, the first is an "escape" value which must be checked for.

How to define a certain time for the getch() function in C?

2 Answers2