Mac address cleaner

mac_cleaner.c

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

int main() {
    char *garbage_mac = "CF97#6#B@3F%23AC$";
    char *clean_mac = malloc(12);
    int length = (int) strlen(garbage_mac);
    int clean_mac_counter = 0;
    for (int i = 0; i < length; i++) {
        char current = garbage_mac[i];
        if (current > 47 && current < 58) {
            //current is number 48-57 is ascii range for 0...9
            clean_mac[clean_mac_counter++] = current;
        } else if (current > 64 && current < 91) {
            //current is capital alphabet. A-Z ascii range 65-90
            clean_mac[clean_mac_counter++] = current;
        } else if (current > 96 && current < 123) {
            //current is small alphabet. a-z ascii range 97-122
            clean_mac[clean_mac_counter++] = current;
        }else{
            printf("Illegal character = %c\n",current);
        }
    }

    printf("Cleaned mac address is = %s\n",clean_mac);
    return 0;
}