win32 - Redirect Input and Output

如果要将exe的输出重定向到cmd，则可以使用匿名管道将子进程的标准输入和输出句柄重定向。请注意，命名管道也可以用于重定向进程I / O

//CMD.exe
#include <windows.h>
#include <tchar.h>
#include <stdio.h>
#include <strsafe.h>

#define BUFSIZE 4096 

HANDLE g_hChildStd_IN_Rd = NULL;
HANDLE g_hChildStd_IN_Wr = NULL;
HANDLE g_hChildStd_OUT_Rd = NULL;
HANDLE g_hChildStd_OUT_Wr = NULL;

HANDLE g_hInputFile = NULL;

void CreateChildProcess(void);
void ReadFromPipe(void);
void ErrorExit(LPCWSTR);

int _tmain(int argc, TCHAR* argv[])
{
    SECURITY_ATTRIBUTES saAttr;

    printf("\n->Start of parent execution.\n");

    // Set the bInheritHandle flag so pipe handles are inherited. 

    saAttr.nLength = sizeof(SECURITY_ATTRIBUTES);
    saAttr.bInheritHandle = TRUE;
    saAttr.lpSecurityDescriptor = NULL;

    // Create a pipe for the child process's STDOUT.   

    if (!CreatePipe(&g_hChildStd_OUT_Rd, &g_hChildStd_OUT_Wr, &saAttr, 0))
        ErrorExit(L"StdoutRd CreatePipe");

    // Ensure the read handle to the pipe for STDOUT is not inherited.

    if (!SetHandleInformation(g_hChildStd_OUT_Rd, HANDLE_FLAG_INHERIT, 0))
        ErrorExit(L"Stdout SetHandleInformation");

    // Create a pipe for the child process's STDIN. 

    if (!CreatePipe(&g_hChildStd_IN_Rd, &g_hChildStd_IN_Wr, &saAttr, 0))
        ErrorExit(L"Stdin CreatePipe");

    // Ensure the write handle to the pipe for STDIN is not inherited. 

    if (!SetHandleInformation(g_hChildStd_IN_Wr, HANDLE_FLAG_INHERIT, 0))
        ErrorExit(L"Stdin SetHandleInformation");

    // Create the child process. 

    CreateChildProcess();

    // Read from pipe that is the standard output for child process. 

    printf("\n->Contents of child process STDOUT:\n\n");
    ReadFromPipe();

    printf("\n->End of parent execution.\n");

    return 0;
}

void CreateChildProcess()
// Create a child process that uses the previously created pipes for STDIN and STDOUT.
{
    TCHAR szCmdline[] = TEXT("Child.exe");
    PROCESS_INFORMATION piProcInfo;
    STARTUPINFO siStartInfo;
    BOOL bSuccess = FALSE;

    // Set up members of the PROCESS_INFORMATION structure. 

    ZeroMemory(&piProcInfo, sizeof(PROCESS_INFORMATION));

    // Set up members of the STARTUPINFO structure.
    // This structure specifies the STDIN and STDOUT handles for redirection.

    ZeroMemory(&siStartInfo, sizeof(STARTUPINFO));
    siStartInfo.cb = sizeof(STARTUPINFO);
    siStartInfo.hStdError = g_hChildStd_OUT_Wr;
    siStartInfo.hStdOutput = g_hChildStd_OUT_Wr;
    siStartInfo.hStdInput = g_hChildStd_IN_Rd;
    siStartInfo.dwFlags |= STARTF_USESTDHANDLES;

    // Create the child process. 

    bSuccess = CreateProcess(NULL,
        szCmdline,     // command line
        NULL,          // process security attributes
        NULL,          // primary thread security attributes
        TRUE,          // handles are inherited
        0,             // creation flags
        NULL,          // use parent's environment
        NULL,          // use parent's current directory
        &siStartInfo,  // STARTUPINFO pointer
        &piProcInfo);  // receives PROCESS_INFORMATION 

     // If an error occurs, exit the application.
    if (!bSuccess)
        ErrorExit(L"CreateProcess");
    else
    {
        // Close handles to the child process and its primary thread.
        // Some applications might keep these handles to monitor the status
        // of the child process, for example. 

        CloseHandle(piProcInfo.hProcess);
        CloseHandle(piProcInfo.hThread);

        // Close handles to the stdin and stdout pipes no longer needed by the child process.
        // If they are not explicitly closed, there is no way to recognize that the child process has ended.

        CloseHandle(g_hChildStd_OUT_Wr);
        CloseHandle(g_hChildStd_IN_Rd);
    }
}

void ReadFromPipe(void)
// Read output from the child process's pipe for STDOUT
// and write to the parent process's pipe for STDOUT.
// Stop when there is no more data.
{
    DWORD dwRead, dwWritten;
    CHAR chBuf[BUFSIZE];
    BOOL bSuccess = FALSE;
    HANDLE hParentStdOut = GetStdHandle(STD_OUTPUT_HANDLE);

    for (;;)
    {
        bSuccess = ReadFile(g_hChildStd_OUT_Rd, chBuf, BUFSIZE, &dwRead, NULL);
        if (!bSuccess || dwRead == 0) break;

        bSuccess = WriteFile(hParentStdOut, chBuf,
            dwRead, &dwWritten, NULL);
        if (!bSuccess) break;
    }
}

void ErrorExit(LPCWSTR lpszFunction)
// Format a readable error message, display a message box,
// and exit from the application.
{
    LPVOID lpMsgBuf;
    LPVOID lpDisplayBuf;
    DWORD dw = GetLastError();

    FormatMessage(
        FORMAT_MESSAGE_ALLOCATE_BUFFER |
        FORMAT_MESSAGE_FROM_SYSTEM |
        FORMAT_MESSAGE_IGNORE_INSERTS,
        NULL,
        dw,
        MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
        (LPTSTR)&lpMsgBuf,
        0, NULL);

    lpDisplayBuf = (LPVOID)LocalAlloc(LMEM_ZEROINIT,
        (lstrlen((LPCTSTR)lpMsgBuf) + lstrlen((LPCTSTR)lpszFunction) + 40) * sizeof(TCHAR));
    StringCchPrintf((LPTSTR)lpDisplayBuf,
        LocalSize(lpDisplayBuf) / sizeof(TCHAR),
        TEXT("%s failed with error %d: %s"),
        lpszFunction, dw, lpMsgBuf);
    MessageBox(NULL, (LPCTSTR)lpDisplayBuf, TEXT("Error"), MB_OK);

    LocalFree(lpMsgBuf);
    LocalFree(lpDisplayBuf);
    ExitProcess(1);
}

//child.exe
#include <windows.h>
#include <stdio.h>

#define BUFSIZE 4096
#pragma warning(disable:4996)

int main(void)
{
    CHAR chBuf[BUFSIZE] = "Hello World";
    DWORD dwRead, dwWritten;
    HANDLE hStdin, hStdout;
    BOOL bSuccess;

    hStdout = GetStdHandle(STD_OUTPUT_HANDLE);
    hStdin = GetStdHandle(STD_INPUT_HANDLE);
    if (
        (hStdout == INVALID_HANDLE_VALUE) ||
        (hStdin == INVALID_HANDLE_VALUE)
        )
        ExitProcess(1);

    // Send something to this process's stdout using printf.
    printf("\n ** This is a message from the child process. ** \n");

    // This simple algorithm uses the existence of the pipes to control execution.
    // It relies on the pipe buffers to ensure that no data is lost.
    // Larger applications would use more advanced process control.

    for (;;)
    {

        // Write to standard output and stop on error.
        bSuccess = WriteFile(hStdout, chBuf, strlen(chBuf)+1, &dwWritten, NULL);

        if (!bSuccess)
            break;
    }
    return 0;
}

重定向exe的输入和输出，重点就是使用CreateProcess将CMD.exe的管道output和input添加到child.exe上面。

微软文档介绍： Creating a Child Process with Redirected Input and Output