int scan_strings(FILE *in, FILE *out)
{
    char buffer[64];
    int i = 0, n = 0;

    for(;;)
    {
        if (fscanf(in, "%*[^" charset "]") != EOF)
        {
            i = 0;
            while (fscanf(in, "%63[" charset "]%n", buffer, &n) == 1)
            {
                if (n < 4 && i == 0)
                {
                    break;
                }
                else
                {
                    i = 1;
                }

                fputs(buffer, out);
            }
            if (i != 0)
            {
                putc('n', out);
            }
        }
        if (feof(in))
        {
            return 0;
        }
        if (ferror(in) || ferror(out))
        {
            return -1;
        }
    }
}