Question

我有一个运行java进程的C ++程序并读取它的输出。我使用了以下MSDN代码：

http://msdn.microsoft.com/en-us/library/ms682499%28v=vs.85%29.aspx

但是，在读取输出的最后一行时

bSuccess = ReadFile(g_hInputFile, chBuf, BUFSIZE, &dwRead, NULL);

bsucces等于1，所以程序继续下一个循环，当到达同一行时，程序只是“飞”，没有异常，停止调试，断点永远不会移动到下一行

我想这是因为没有EOF表示停止阅读。但是，java 没有 EOF charcater。 java程序只是这样做：

System.out.close();

结束。

我可以在C ++ \ Java代码中做些什么来修复它？

修改

这是代码。

它不适用于任何控制台应用程序，读取结束然后“挂起”。

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;
PROCESS_INFORMATION piProcInfo;

void CreateChildProcess()
// Create a child process that uses the previously created pipes for STDIN and STDOUT.
{
    std::string d=processLoaction;
    TCHAR *cmdline=new TCHAR[d.size()+1];
    cmdline[d.size()]=0;
    std::copy(d.begin(),d.end(),cmdline);
   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.dwFlags |= STARTF_USESTDHANDLES;

// Create the child process. 
   bSuccess = CreateProcess(NULL, cmdline, NULL, NULL, TRUE, 0, NULL, NULL, &siStartInfo, &piProcInfo);  // receives PROCESS_INFORMATION 

   // If an error occurs, exit the application. 
   if ( ! bSuccess ) 
      throw new Exception("Failed to create process");
   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 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,status; 
   CHAR chBuf[BUFSIZE]; 
   BOOL bSuccess = FALSE;
   HANDLE hParentStdOut = GetStdHandle(STD_OUTPUT_HANDLE);
   BOOL res;
   for (;;) 
   { 
      bSuccess = ReadFile( g_hChildStd_OUT_Rd, chBuf, BUFSIZE, &dwRead, NULL);
      if( ! bSuccess || dwRead == 0 ) 
          break; 
      chBuf[dwRead] = NULL;
      bSuccess = WriteFile(hParentStdOut, chBuf, dwRead, &dwWritten, NULL);
      if (! bSuccess ) 
          break; 
   } 

}

int main(int argc, char** argv)
{ 
          //run the Jar to validate manifest & jeff
          SECURITY_ATTRIBUTES saAttr; 

          // 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) )
              throw new Exception("faild to create a pipe for the child process's STDOUT");

          // Ensure the read handle to the pipe for STDOUT is not inherited.
          if ( ! SetHandleInformation(g_hChildStd_OUT_Rd, HANDLE_FLAG_INHERIT, 0) )
              throw new Exception("Read handle to the pipe for STDOUT is inherited");
          CreateChildProcess();
          ReadFromPipe();
            ...
}

Answer 1

问题似乎在您链接的页面的一些注释中得到解决：您必须在创建子进程后关闭管道的写入端，但在开始从另一侧读取之前。如果你没有这样做，即使子进程关闭了它的输出，管道的写入端仍然打开（由父进程），因此永远不会达到EOF。

啊，别忘了关闭父进程的所有句柄。链接页面中的示例没有，它泄漏了！

c ++读取java进程输出

1 个答案: