f

int main(void)
{
    char eol = 0;
    char input[8] = "";

    while (1)
    {
        printf("> ");

        if(scanf("%7[0-9]%c", input, &eol) != 2 || eol != '\n') {
            printf("bad\n");

            scanf("%*[^\n]");
            scanf("%*c");
        }
        else {
            printf("good\n");
        }

        printf("[len = %d data = %s]\n", strlen(input), input);
    }

    return 0;
}