c - 需要帮助在 Windows 上严重重定向计时器程序的输入和输出

Question

我希望程序能够重定向两者的输入和输出 父进程和子进程。例如，

parent "child.exe > child_output.txt" > parent_output.txt

parent 称呼 child 。子输出到child_output，父输出到父输出。

下面的示例代码应该可以工作，但是却不能。为了方便起见，我将子级的重定向运算符硬编码在字符串“ToBeRun”中，而不是像主程序中那样将其作为参数传递。

如果在命令行中没有向父级传递任何参数，则子级输出将正确重定向到 child_output.txt。但是，如果您在命令行上重定向父级的参数，例如通过调用parent.exe >parent_output.txt，则父级输出不会重定向。 Parent_output.txt 已创建，但在程序完成时为空。

#include <windows.h>

// COPY PASTED FROM Martins Mozeiko on Handmade Network:
// https://hero.handmade.network/forums/code-discussion/t/94
// these shouldn't have to be in here, but hey! What can you do?
#pragma function(memset)
void *memset(void *dest, int c, size_t count)
{
    char *bytes = (char *)dest;
    while (count--)
    {
        *bytes++ = (char)c;
    }
    return dest;
}

#pragma function(memcpy)
void *memcpy(void *dest, void *src, size_t count)
{
    char *dest8 = (char *)dest;
    char *src8 = (char *)src;
    while (count--)
    {
        *dest8++ = *src8++;
    }
    return dest;
}
/* Based on this msdn article
 * https://msdn.microsoft.com/en-us/library/windows/desktop   /ms682512(v=vs.85).aspx
 */
int main(void)
{
    // init structures for child process
    STARTUPINFO si;
    PROCESS_INFORMATION pi;
    ZeroMemory( &si, sizeof(si) );
    si.cb = sizeof(si);
    ZeroMemory( &pi, sizeof(pi) );

    // start child process and wait for it to finish
#if 0
    char *ToBeRun = "/C child.exe > child_result.txt";
#else
    // for your convenience, so you don't have to compile a sample child.exe
    char *ToBeRun = "/C dir > child_result.txt";
#endif
    if( !CreateProcess("C:\\WINDOWS\\system32\\cmd.exe", // Module name
                       ToBeRun,     // Command line
                       NULL,        // Process handle not inheritable
                       NULL,        // Thread handle not inheritable
                       FALSE,       // Set handle inheritance to FALSE
                       0,           // No creation flags
                       NULL,        // Use parent's environment block
                       NULL,        // Use parent's starting directory 
                       &si,         // Pointer to STARTUPINFO structure
                       &pi)  // Pointer to PROCESS_INFORMATION structure
    ) 
    {
        // create process failed
        return 1;
    }
    WaitForSingleObject(pi.hProcess, INFINITE);

    // print parent output string
    char String[] = "This is the parent's output";
    int StringLength = sizeof(String) / sizeof(String[0]);
    DWORD CharsWritten;
    HANDLE Handle = GetStdHandle(STD_OUTPUT_HANDLE);
    WriteConsole(Handle, String, StringLength, &CharsWritten, NULL);

    // close process and thread handles. 
    CloseHandle( pi.hProcess );
    CloseHandle( pi.hThread );
    return 0;
}

// required for compiling without CRT
void mainCRTStartup(void)
{
    int Result = main();
    ExitProcess(Result);
}

Answer 1

我回答了我自己的问题:简单地说，WriteConsole() 在写入重定向文件时失败。

因此，在写入重定向文件时，您需要使用恰当命名的 WriteFile()。

WriteFile() 适用于重定向输出和常规控制台输出，如 Harry Johnston已经有用地指出了，所以你可以在这两种情况下使用它。我就是这么做的。

或者，特别是如果您使用 Unicode，您可以采用 MSDN's advice并通过调用 GetConsoleMode 检查 HANDLE 是否是文件句柄或控制台句柄。如果 GetConsoleMode 返回 0，则它不是控制台。

你为什么要这样做？ WriteConsole 与 WriteFile 不同，它是一个可以成为 unicode 或 ASCII 函数的宏，具体取决于是否定义了 UNICODE。

From MSDN :

The ReadFile and WriteFile functions, or the ReadConsole and WriteConsole functions, enable an application to read console input and write console output as a stream of characters. ReadConsole and WriteConsole behave exactly like ReadFile and WriteFile except that they can be used either as wide-character functions (in which text arguments must use Unicode) or as ANSI functions (in which text arguments must use characters from the> Windows character set). Applications that need to maintain a single set of sources to support either Unicode or the ANSI character set should use ReadConsole and WriteConsole.