Question

Currently, I have a loop in my program that has the format:

  #include<stdio.h>

    int main()
    {
    int n;

         while(1)
         {
         printf("Enter a positive number, n");

         scanf("%d",&n);

         if(n>0)
             {
              break;
             }
          }
      }

My intention in using the if(n>0) statement was to exit the loop if and only if the user enters a positive integer. However, if the user types in the character “g”, for example, the loop will still break, as the ASCII value will be interpreted. How do I form this loop so that it breaks just when the user enters a positive integer value for n?

Answer 1

Check the return value of scanf which returns the number of successful inputs read:

int rc = scanf("%d",&n);

if (rc==1 && n>0) {
  ...
}

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I would suggest you to use fgets to read the input into a string and convert into integer using strtol as scanf is a poor choice for the reason said by @paddy.