如何使用system（）函数[C ++]在C ++中存储cmd内存 [英] How to Store cmd memory in c++ using system() Function [C++]

问题描述

看下面的代码！您将了解我想要的：

Look at the code below! You will understand what I want:

#include <iostream>
#include <windows.h>

    using namespace std;

    int main()
    {  
       system("set plock=24865");
       system("echo %plock%"); // I know this will not work.But How to make it work?

     return 0;
    }

推荐答案

嗯，正如您所说，那行不通。重要的是要理解为什么：： system 调用会生成一个子进程来运行Shell，然后设置环境变量在该子进程中，该进程立即终止。

Well, as you say, that won't work. What's important to understand is why: The system call spawns a child process to run the shell, and then you're setting an environment variable in that child process, which promptly terminates.

因此，您的问题可能过于具体，因为它询问如何使用 system（）；简短的答案是你不能。 （答案很长，您可以在注册表中设置环境变量，但是仅当您打算将其作为对计算机的永久配置更改时才有意义。如果您只是想设置一个变量以供后续 system（）来自同一程序的调用..）

So perhaps your question is over-specific in that it asks how to do this "using system()"; short answer is you can't. (Long answer is you could set the environment variable in the registry, but that's only sensible if you intend this to be a permanent configuration change to the computer. It's not the best idea if you just mean to set a variable for use in subsequent system() calls from the same program..)

因此，您可以使用 SetEnvironmentVariable（）函数，它将在您当前的过程中（而不是在即将消失的孩子中）设置环境变量。

So instead you could use the SetEnvironmentVariable() function, which will set the environment variable in your current process (instead of in a child that's about to go away).

更新-在问题的注释线程中还提到了另一个选项；但它假定您可以设置变量并立即运行依赖于此变量的任何/所有命令。在这种情况下，您可以将所有命令打包到一个系统调用中，最简单的方法是使用批处理脚本...

UPDATE - There is one other option, alluded to in the question's comment thread; but it assumes that you can set the variable and immediately run any/all commands that depend on it right after. In the case where you can do that, you could pack all the commands into one system call, most simply with a batch script...

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