Question

I am trying to write a program that reads a string (in my case a domain name). What I am struggling with is how to traverse through the array and see if there are any invalid characters in the string such as a semi colon or a space. Here is what I have as of now.

#include <stdio.h>

int main()
{

   char min[1];
   char max[253];
   char domain[253];

printf("Enter a domain: ");
scanf("%s", domain);

   return 0;
}

Answer 1

#include <stdio.h>

/**
 * Given a character this function returns 0 if it's not valid and 1 if it's valid
 */
int is_valid(char ch) {
    return !(ch == ';' || ch == ' ');   // you can add more invalid characters here..
}

/**
 * Given a domain this function returns 0 if it's not valid and 1 if it's valid
 */
int is_domain_valid(char domain[]) {
    int i = 0;
    while (domain[i]) {
        if (!is_valid(domain[i])) {
            return 0;
        }
        i++;
    }
    return 1;
}

int main() {

    char min[1];
    char max[253];
    char domain[253];

    printf("Enter a domain: ");
    scanf("%s", domain);

    if (is_domain_valid(domain)) {
        printf("%s is a valid domain\n", domain);
    }

    return 0;
}