Awkward behaviour of GetInt()

Question

So i am working on a linked list program and am using functions like insert, delete and search which require taking input from the user and so i tried using GetInt() from the CS50 library for the same but everytime anyone of the above functions is being executed, GetInt() is directly providing Retry: prompt even before i am giving an input. I have not been able to find out why this is happening and eventually i replaced it with scanf but i am still curious to know why GetInt() behaved like that.
I am adding the code snippets and screen shots for better understanding of my problem.
The following is the search function where i am using the GetInt() function.

   void search(void)
   {
       // prompt user for number
       printf("Number to search for: \n");
       //EVEN IF NEWLINE CHARACTER IS REMOVED THE PROBLEM REMAINS 
       int n = GetInt(); //THIS IS CAUSING THE PROBLEM IN MY OPINION

       // get list's first node
       node* ptr = first;
       // search for number
      while (ptr != NULL)
      {
          if (ptr->num == n)
          {
              printf("\nFound %i!\n", n);
              sleep(1);
              break;
          }
          ptr = ptr -> next;
      }
      printf("\nProvided number is not present \n");
    }   

Attached below is the screenshot of the terminal where i have run my program, i have highlighted my problem in yellow text.

I have earlier added 4 elements into my linked list and when i am trying to search for any number the prompt is always followed by Retry prompt. So if anyone could explain why this might be happening it would be a great help.

Answer 1

The only reason that GetInt() would return "Retry" is if it recieved a non-integer from standard input (ie, from your keyboard), as the definition says:

/*
 * Reads a line of text from standard input and returns it as an
 * int in the range of [-2^31 + 1, 2^31 - 2], if possible; if text
 * does not represent such an int, user is prompted to retry.  Leading
 * and trailing whitespace is ignored.  For simplicity, overflow is not
 * detected.  If line can't be read, returns INT_MAX.
 */

int GetInt(void)
{
    // try to get an int from user
    while (true)
    {
        // get line of text, returning INT_MAX on failure
        string line = GetString();
        if (line == NULL)
            return INT_MAX;

        // return an int if only an int (possibly with
        // leading and/or trailing whitespace) was provided
        int n; char c;
        if (sscanf(line, " %d %c", &n, &c) == 1)
        {
            free(line);
            return n;
        }
        else
        {
            free(line);
            printf("Retry: ");
        }
    }
}

I've used GetInt() a lot and have never seen it return 'Retry' without some keyboard entry, even only a carriage return. As you can see, the function will not return unless it receives a valid value from standard input.

You might try running your program on http://run.cs50.net to eliminate any appliance problem.