scanf() driving me crazy

[scorpio2002]

Hi there. I'm new to the forum ;-)

I'm having really a bad time with the scanf(9 function. Take a look at this:

#include <stdio.h>
 
int main() {
    char up_key,
        down_key,
        right_key,
        left_key;
 
    int speed;    
    printf("**** Configurazione delle opzioni ****\n");
    printf("Immetti il valore up_key: ");
    scanf("%c", &up_key);
    printf("Immetti il valore down_key: ");
    scanf("%c", &down_key);
    printf("Immetti il valore right_key: ");
    scanf("%c", &right_key);
    printf("Immetti il valore left_key: ");
    scanf("%c", &left_key);
    printf("Immetti il timeout del gioco (più è alto, più il gioco è lento): ");
    scanf("%d", &speed);
 
    }
 

That is supposed to take some input from the user. The proble is that when I execute it, here's what I get:

**** Configurazione delle opzioni ****
Immetti il valore up_key: e
Immetti il valore down_key: Immetti il valore right_key: e
Immetti il valore left_key: Immetti il timeout del gioco (più è alto, più il gioco è lento): 5

Basically, it skeeps the 2nd and the 4th scanf(). I can't see any reason for that. I don't think it's a bug in gcc (the compiler i'm using)...

Thanks in advance. That's really gonna drive me crazy :(

[sundarr]

It seems that repeated scanfs are not flushing out the read character from the terminal. so what u do is to include a fflush(stdin) before your every scanf call to avoid erronous behaviours.
#include <stdio.h>

int main() {
char up_key,
down_key,
right_key,
left_key;

int speed;
printf("**** Configurazione delle opzioni ****\n");
printf("Immetti il valore up_key: ");
scanf("%c", &up_key);
fflush(stdin);
printf("Immetti il valore down_key: ");
scanf("%c", &down_key);
fflush(stdin);
printf("Immetti il valore right_key: ");
scanf("%c", &right_key);
fflush(stdin);
printf("Immetti il valore left_key: ");
scanf("%c", &left_key);
fflush(stdin);
printf("Immetti il timeout del gioco (più è alto, più il gioco è lento): ");
scanf("%d", &speed);

}

This should work well for you.

[horace1]

When using the %c conversion specification with scanf() it returns all characters including spaces and <RETURN> (or <ENTER>) characters

When you type in your input you hit the character followed by the <Enter> key.
The first scanf() reads the character and the second scanf() (which should read your next character input) reads the <RETURN> character. What you can do is to tell scanf() to read up the the next non-white space character (skipping white-space). You do this by putting a space in the conversion specification, e.g. " %c"

#include <stdio.h>
 
int main() {
    char up_key,
        down_key,
        right_key,
        left_key;
 
    int speed;    
    printf("**** Configurazione delle opzioni ****\n");
    printf("Immetti il valore up_key: ");
    scanf(" %c", &up_key);
    printf("Immetti il valore down_key: ");
    scanf(" %c", &down_key);
    printf("Immetti il valore right_key: ");
    scanf(" %c", &right_key);
    printf("Immetti il valore left_key: ");
    scanf(" %c", &left_key);
    printf("Immetti il timeout del gioco (più è alto, più il gioco è lento): ");
    scanf("%d", &speed);
 
    }