//kontrola validity argumentov
    if  (strcmp (argv[1], "select") == 0)||
        (strcmp (argv[1], "min") == 0)||
        (strcmp (argv[1], "max") == 0)||
        (strcmp (argv[1], "sum") == 0)||
        (strcmp (argv[1], "avg") == 0)||
        {
    printf("%s\n",argv[1]);
    }