在附加的控制台中输入文本时，如何避免“未被识别为内部或外部命令，可操作程序或批处理文件”？

Question

I attach existing console form C++ program. Output works fine, but when I try to put some input in console, terminal originally running there try to handle it. Program code is here:

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

int main(int argc, char **argv)
{
    pid_t pid = atoi(argv[1]);
    BOOL fret = FreeConsole();
    if  (!fret)
    {
        std::cerr << "ERR" << GetLastError() << std::endl;
    }

    BOOL aret = AttachConsole(pid);

    if  (!aret)
    {
        std::cerr << "ERR" << GetLastError() << std::endl;
    }

    SetConsoleTitleA("TTTTTTTT");

    for (int ii = 0; ii < 10; ii++)
    {
        std::cout << "ii " << ii << std::endl;
    }

    int kk;
    std::cin >> kk;

    std::cerr << "kk " << kk << std::endl;

    return 0;
}

When I run cmd, find out PID, run my program and then write for example 12 and enter, this is result:

C:\>ii 0
ii 1
ii 2
ii 3
ii 4
ii 5
ii 6
ii 7
ii 8
ii 9
12
'12' is not recognized as an internal or external command,
operable program or batch file.

When I try once again write 12, it works better (but there is still C:>)

C:\>12
kk 12
C:\>

Edit: I need redirect stdin, stdout, and stderr to console, I can run something else then cmd or send some command to cmd.

Answer 1

"is not recognized as an internal or external command, operable program or batch file." is a standard cmd.exe error message. cmd.exe is already waiting for input when you do AttachConsole so the first input is sent to cmd.exe and that is why you get that error message. Replace the first number input with a command like dir and you will see that this input is received by cmd.exe.

The second time it works but mostly by accident. cmd.exe is probably busy with other things so your application gets the input before cmd.exe is able to "listen" to stdin again. cmd.exe prints the prompt (the "path" + > ) because that's what it does after each command has been performed.

cmd.exe does not expect to share the console with anyone else and its normal mode of operation is to:

1. Read and parse a line from stdin .
2. Execute. Wait for the operation to complete if the command is an internal command or a external console application. It does not wait for GUI applications.
3. Print %PROMPT%.
4. Goto 1.

Even if you could convince cmd.exe to coexist with you, what you are doing is probably undefined behavior because you are mixing low-level native Windows console functions ( AttachConsole ) with high-level C++ I/O functions ( std::cout & std::cin ). Assuming you are using the Microsoft CRT you could use _open_osfhandle + _dup2 to correctly assign the native console handle but you would still have issues with cmd.exe and there is no way to work around it.