Filter code generation

If you want to generate a filter code, please use the snippet below:

int main(int ac, char** av) {
    if (ac != 2 || strlen(av[1]) != 4) {
        printf("Usage: %s four_letter_name\n", av[0]);
        return 1;
    }
    printf("0x");
    for (int i = 0; i < 4; ++i) {
        printf("%X", av[1][i]);
    }
    printf("\n");
    return 0;
}

To compile it: gcc generator.c -o filter_code_generator. To use it: ./filter_code_generator xmpl (it will return 0x786D706Cc).