getchar() in switch()-function doesn't work

Question

so I was trying to program my first project on my own and already have some troubles concerning the getchar()-function.

What I want to do is to get user input without having to press enter. The user-input than should "activate" the case equivalent to the input (e.g. input = case = 1). Instead of that I still have to press enter but then only the default-command gets called.

I saw, that there are some questions about it but non of them really helped me out. here is my code:

#include <stdio.h>
#include "open_txt.h"

int main (){

    printf("\n\n\tAdressbook\n\n");

    printf("Main menu: \n\n");

    printf("1. Add contact\n");
    printf("2. Edit contact\n");
    printf("3. Search contact\n");

    int ui;
    ui = getchar();

    switch(ui){

        case 1:
            printf("\n\nADD CONTACT\n\n");
            break;
        case 2:
            printf("\n\nEDIT CONTACT\n\n");
            break;
        case 3:
            printf("\n\nSEARCH CONTACT\n\n");
            break;
        default:
            printf("That's not an option!\n");
    }
    return 0;
}

Use a debugger to see the value of ui. You will find that "1" is 49, "2" is 50, etc. — Dabbler, Dec 12 '20 at 15:33
Does this answer your question? [Capture characters from standard input without waiting for enter to be pressed](https://stackoverflow.com/questions/421860/capture-characters-from-standard-input-without-waiting-for-enter-to-be-pressed) — Andreas Wenzel, Dec 12 '20 at 15:36
I think you will find here some helpful answers : [https://stackoverflow.com/questions/38211864/dynamically-read-user-input-strings-in-c/38212264](https://stackoverflow.com/questions/38211864/dynamically-read-user-input-strings-in-c/38212264) — Badreddine BOUSBA, Dec 12 '20 at 15:42

score 2 · Answer 1 · answered Dec 12 '20 at 15:34

2

The getchar function returns the key pressed as a character code. So if someone presses 1 then what gets returned is the character '1', not the value 1.

Use character constants instead of numeric constants in your switch:

    case '1':
        printf("\n\nADD CONTACT\n\n");
        break;
    case '2':
        printf("\n\nEDIT CONTACT\n\n");
        break;
    case '3':
        printf("\n\nSEARCH CONTACT\n\n");
        break;

answered Dec 12 '20 at 15:34

dbush

205,898
23
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Oh wow, thanks! But still I have to press enter, is there any way to solve it as well? Or is getchar() the wrong path to take here? – Dec 12 '20 at 15:37
then you have to use `getch` instead of `getchar`, as @Krishna said – lfalkau Dec 12 '20 at 15:38
It is still not working. Either way it waits until i press enter... – Dec 12 '20 at 16:13

score 2 · Answer 2 · answered Dec 12 '20 at 15:35

2

What I want to do is to get user input without having to press enter.

Then you should use getch() function. getch() reads a single character from the keyboard. But it does not use any buffer, so the entered character is immediately returned without waiting for the enter key.

answered Dec 12 '20 at 15:35

Krishna Kanth Yenumula

2,533
2
14
26

It seems like C is making fun of me lol. So i clearly do something wrong, since it is still not working.. – Dec 12 '20 at 15:55
Note that the function `getch` is not part of ISO C. It is a platforms-specific extension. However, it seems that both Microsoft Windows and Linux offer support for this function, but it will probably be unavailable on some other platforms. – Andreas Wenzel Dec 12 '20 at 15:56

score 0 · Answer 3 · answered Dec 12 '20 at 15:41

Here ,switch statement return a caracter not a value ,so you should write like this : '1' '2' '3'

#include <stdio.h> 
#include "open_txt.h"

int main (){

printf("\n\n\tAdressbook\n\n");

printf("Main menu: \n\n");

printf("1. Add contact\n");
printf("2. Edit contact\n");
printf("3. Search contact\n");

int ui;
ui = getchar();

switch(ui)
{
  case '1':
    printf("\n\nADD CONTACT\n\n");
    break;
  case '2':
    printf("\n\nEDIT CONTACT\n\n");
    break;
  case '3':
    printf("\n\nSEARCH CONTACT\n\n");
    break;
  default:
    printf("That's not an option!\n");

   }
}

getchar() in switch()-function doesn't work

3 Answers3