Question

#define MAGIC_NUMBER //place your favourite integer here 
#include <stdlib.h>
#include <stdio.h>

int main()
{
    int input,i;
    for(int i=0;i<100;i++)
    {
        scanf("%d",&input);
        if(input== MAGIC_NUMBER)
            printf("%d ",input);                
        else
            printf("Invalid value\n");
    }
    system("pause");
    return 0;
}

This program crashes when a non-integer value is entered. I want to get scanf back to normal work after the character had been scanned.

Answer 1

From scanf man-page:

These functions return the number of input items assigned.

So you can check the return value and read-in bad values to discard if there is an error:

#include <stdlib.h>
#include <stdio.h>

int main()
{
    int input,i;

    for(i=0;i<100;i++)
    {   
      if (scanf("%d",&input) == 1) { // check if success

        if(input== MAGIC_NUMBER)
        {
          printf("%d ",input);    
        }
        else
          printf("Invalid value\n");
      } else {  // discard input
        int c;
        while ((c = getchar()) != '\n' && c != EOF);
      }   

    }   

    return 0;
}