命令提示符如何知道何时等待退出？

我试图用 c # 重新编写一个命令提示符。我想知道命令提示符如何知道何时等待进程开始退出，何时不等待被调用的进程退出。

例如，如果您键入命令提示符“ notepad”，记事本将启动，但您仍然可以执行其他命令。但是，如果您打开一个实用程序，比如 more. com、 ping.exe 或另一个实用程序，它将等待正在执行的程序完成，然后再让您执行另一个命令。

命令提示符如何知道何时等待退出，以及如何在 C # 中模拟这种行为？

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最佳答案

If the application is a Win32 GUI application, it will just run and command prompt won't wait for it to exit.

If the application is a console application, it will run in the command prompt and you'll need to wait for it to finish to get the command prompt back.

EDIT:

OK. It seems you need technical explanation. If you want to emulate the same feature in your application, you can check IMAGE_OPTIONAL_HEADER of EXE files here.

Inside IMAGE_OPTIONAL_HEADER, there is:

 WORD                 Subsystem;

If SubSystem == 0x02 it means it's a GUI application.

If SubSystem == 0x03 it means it's a command prompt app.

EDIT 2:

If you want to see it in action:

  1. Download http://www.ntcore.com/exsuite.php

  2. Copy calc.exe or notepad.exe to your desktop

  3. Open copied calc.exe in CFF Explorer

  4. Navigate to Nt Headers -> Optional Headers

  5. Change SubSystem from 0x002 to 0x003

  6. Save it

Now run the new modified calc and you'll see the command prompt wait for it to be terminated.

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When you start a new process, a GUI application in this context that actually works outside the boundaries of the prompt, the prompt will not wait. But, if you run a command that works entirely under the boundaries of the current instance of a prompt, it waits.

So, command notepad just starts the Notepad application and leaves control of application. While, command ipconfig runs under a domain (no this is not application domain), of the prompt.

To extremely generalize, when you use Process.Start in your C# equivalent, do not wait. It anyway will not.

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The default from a command prompt is to spawn the GUI program in a separate process/fork. However, you can run notepad (or other GUI program) inline with your command prompt / shell script:

start /w notepad.exe

This way, the command prompt / shell script only continues after the notepad.exe process has terminated.

Hope this helps, TW


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