windows 进程通信之管道详解 ：

在项目中用到了Windows进程通信 ，需要用管道读子进程的标准输入，输出，于是研究了MSDN上的相关代码

代码源地址:https://msdn.microsoft.com/en-us/library/windows/desktop/ms682516(v=vs.85).aspx

ps :a代码中需要注意的是在CreateChildProcess中通过

siStartInfo.hStdErro=g_hChildStd_OUT_Wr;

siStartInfo.hStdOutput=g_hChildStd_OUT_Wr;

siStartInfo.HStdInput-g_hChildStd_IN_Rd;

通过以上代码，将子进程的标准错误输出，标准输出，标准输入都重定向为管道，这些管道是在主进程中创建的，可以被子进程继承！

#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 WriteToPipe(void);void ReadFromPipe(void);void ErrorExit(PTSTR);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(TEXT("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(TEXT("Stdout SetHandleInformation"));// Create a pipe for the child process's STDIN. if (!CreatePipe(&g_hChildStd_IN_Rd, &g_hChildStd_IN_Wr, &saAttr, 0))ErrorExit(TEXT("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(TEXT("Stdin SetHandleInformation"));// Create the child process. CreateChildProcess();// Get a handle to an input file for the parent. // This example assumes a plain text file and uses string output to verify data flow. if (argc == 1)ErrorExit(TEXT("Please specify an input file.\n"));g_hInputFile = CreateFile(                                        ///此处是需要打开本地的一个文本文件，，在项目property中设置参数argv[1],GENERIC_READ,0,NULL,OPEN_EXISTING,FILE_ATTRIBUTE_READONLY,NULL);if (g_hInputFile == INVALID_HANDLE_VALUE)ErrorExit(TEXT("CreateFile"));// Write to the pipe that is the standard input for a child process. // Data is written to the pipe's buffers, so it is not necessary to wait// until the child process is running before writing data.WriteToPipe();printf("\n->Contents of %s written to child STDIN pipe.\n", argv[1]);// Read from pipe that is the standard output for child process. printf("\n->Contents of child process STDOUT:\n\n", argv[1]);ReadFromPipe();printf("\n->End of parent execution.\n");// The remaining open handles are cleaned up when this process terminates. // To avoid resource leaks in a larger application, close handles explicitly. return 0;}void CreateChildProcess()// Create a child process that uses the previously created pipes for STDIN and STDOUT.{//TCHAR szCmdline[] = TEXT("C:\\Project3.exe");LPTSTR szCmdline = _tcsdup(_TEXT("C:\\Project3.exe"));//这是子进程可执行文件的路径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(TEXT("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);}}void WriteToPipe(void)// Read from a file and write its contents to the pipe for the child's STDIN.// Stop when there is no more data. {DWORD dwRead, dwWritten;CHAR chBuf[BUFSIZE];BOOL bSuccess = FALSE;for (;;){bSuccess = ReadFile(g_hInputFile, chBuf, BUFSIZE, &dwRead, NULL);if (!bSuccess || dwRead == 0) break;bSuccess = WriteFile(g_hChildStd_IN_Wr, chBuf, dwRead, &dwWritten, NULL);if (!bSuccess) break;}// Close the pipe handle so the child process stops reading. if (!CloseHandle(g_hChildStd_IN_Wr))ErrorExit(TEXT("StdInWr CloseHandle"));}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(PTSTR 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);}

 

下面是子进程代码，我把子进程编译好命名为Project3 可执行文件为Project3.exe ，在上面的主进程需要调用这个可执行文件的绝对路径，这点需要注意，源网址直接调用了一个“child”,容易让新上手的人摸不着头脑，因为它省略了后缀.exe 和程序路径

#include <windows.h>#include <stdio.h>#define BUFSIZE 4096 int main(void){CHAR chBuf[BUFSIZE];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 (;;){// Read from standard input and stop on error or no data.bSuccess = ReadFile(hStdin, chBuf, BUFSIZE, &dwRead, NULL);if (!bSuccess || dwRead == 0)break;// Write to standard output and stop on error.bSuccess = WriteFile(hStdout, chBuf, dwRead, &dwWritten, NULL);if (!bSuccess)break;}return 0;}

程序执行结果如下：

      父进程从11.txt读数据，并把这些数据写到g_hChildStd_IN_Wr 中。子进程从管道中通过g_hChildStd_IN_Rd获得数据，再通过g_hChildStd_OUT_Wr中写到管道2中。父进程之后再从管道g_hChildStd_OUT_Rd中读取数据并显示。