c++ 获取环境变量 getenv

来源：https://en.cppreference.com/w/cpp/utility/program/getenv

#include <cstdlib>
#include <iostream>

int main()
{
    if (const char* env_p = std::getenv("PATH"))
        std::cout << "Your PATH is: " << env_p << '\n';
}

运行结果：

Your PATH is: /usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games