Pset 2 - Validating the Key

Question

I'm very new to all this and so am struggling a bit with the for loop. Here is my code:

#include <stdio.h>
#include <stdlib.h>
#include <cs50.h>
#include <string.h>
#include <ctype.h>

int main(int argc, string argv[])
{
    // Promts user if inputs more than one command-line argument
    if (argc != 2)
    {
        printf("Usage: ./caesar key\n");
        return 1;
    }
    
    // Prompts user if key is composed of characters other than digits
    for (int i = 0, n = strlen(argv[1]); i < n; i++)
    {
        if (!isdigit(argv[1][i]))
        {
            printf("Usage: ./caesar key\n");
            return 1;
        }
        else
        {
            printf("Success!\n");
            return 0;
        }
    }    
}

I'm not sure I understand how I can make my loop work for "./caesar 20x", so that it prompts the user for another key. I've been trying to get my head around it and can't figure itout, would appreciate any leads.

Answer 1

It's only supposed to terminate the program with the usage message, not prompt for a new key.

The real problem here is that it will only check the first character. Think about it. If a single char is not a number, the test fails and the program needs to terminate. BUT, it's only a success once all the characters are checked. The code needs to check all the characters (finish the loop) before there is success and the success message printed.

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