在C++中使用getopt庫處理多參數情況下的應用如下：

#include <iostream>
#include <unistd.h>

int main(int argc, char *argv[])
{
    int option;
    bool flag1 = false;
    bool flag2 = false;
    std::string arg1;
    std::string arg2;

    while ((option = getopt(argc, argv, "ab:c:")) != -1)
    {
        switch (option)
        {
        case 'a':
            flag1 = true;
            break;
        case 'b':
            arg1 = optarg;
            break;
        case 'c':
            flag2 = true;
            arg2 = optarg;
            break;
        case '?':
            if (optopt == 'b' || optopt == 'c')
            {
                std::cerr << "Option -" << optopt << " requires an argument." << std::endl;
            }
            else if (isprint(optopt))
            {
                std::cerr << "Unknown option `-" << optopt << "'." << std::endl;
            }
            else
            {
                std::cerr << "Unknown option character `\\x" << optopt << "'." << std::endl;
            }
            return 1;
        default:
            abort();
        }
    }

    std::cout << "flag1: " << std::boolalpha << flag1 << std::endl;
    std::cout << "arg1: " << arg1 << std::endl;
    std::cout << "flag2: " << std::boolalpha << flag2 << std::endl;
    std::cout << "arg2: " << arg2 << std::endl;

    return 0;
}

在上面的示例中，使用getopt函數解析命令行參數，并根據參數選項設置相應的標志和參數值。通過指定選項的字母和可能的參數，可以處理多個參數的情況。最后輸出各個參數的值。