Avoiding an infinite while loop

Question

I'm stuck on a while loop exercise. The program seems to work fine as long as I only enter integers. However, if I enter a character, a symbol or a real number with decimals (even integers such as 1.0), I get a infinite loop.

int main() 
{
    int num;
    printf("Enter an odd number 1 and 10.");
    while(1) 
       {
        printf("\n\nEnter : ");
        scanf("%d", &num);

        if(num == 0)
            break;
        else if(num < 0 || num > 10)
            printf("You entered number is beyond the range.");
        else if(num % 2 == 0)
            printf("You entered an even number.");
        else
            printf("You entered a correct number.");
       }

   printf("You are exiting the program.");      
   return 0;
}

Check the result of scanf. – Paul Ogilvie Jun 06 '18 at 12:34 — Paul Ogilvie, Jun 06 '18 at 12:34
`num` isn't changed if input is incorrect. – Jean-François Fabre Jun 06 '18 at 12:35 — Jean-François Fabre, Jun 06 '18 at 12:35
@Fabio_MO there is a conditional break!! – Sourav Ghosh Jun 06 '18 at 12:37 — Sourav Ghosh, Jun 06 '18 at 12:37

score 0 · Answer 1 · answered Jun 06 '18 at 12:45

0

However, if I enter a character, a symbol or a real number with decimals ? Then you have undefined behaviour as scanf() expecting int argument but you are providing other than int argument.

even integers such as 1.0 ? No, 1.0 is not an integer it's a real number.

Check the return value of scanf() to know whether it's success or fail. Open man 3 scanf and analyze. For e.g

int ret = 0;

ret = scanf("%d",&num);

if(ret != 1) { /* Error handling */ }

answered Jun 06 '18 at 12:45

Achal

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I appreciate your help. Your method was simple yet it works perfectly. Thanks again! – Jero Won Jun 07 '18 at 04:52

Avoiding an infinite while loop

1 Answers1