How to test input is sane

Question

Consider the following simple C program.

//C test

#include

int main()
{
   int a, b, c;

   printf(\"Enter two numbers to add\\n\");
   scan         


        

Answer 1

You can use the following macro

#define SCAN_ONEENTRY_WITHCHECK(FORM,X,COND) \
do {\
    char tmp;\
    while(((scanf(" "FORM"%c",X,&tmp)!=2 || !isspace(tmp)) && !scanf("%*[^\n]"))\
            || !(COND)) {\
        printf("Invalid input, please enter again: ");\
    }\
} while(0)

and you call it in this way in the main

int main()

{
    int a, b, c;

    printf("Input first integer, valid choice between 0 and 10: ");
    SCAN_ONEENTRY_WITHCHECK("%d",&a,(a>=0 && a<=10));

    printf("Input second integer, valid choice between 0 and 10: ");
    SCAN_ONEENTRY_WITHCHECK("%d",&b,(b>=0 && b<=10));

    c = a + b;
    printf("Sum of entered numbers = %d\n",c);
    return 0;

}

for more detail concerning this macro please refer to: Common macro to read input data and check its validity