Windows：如何使用CreateProcess停止重定向Stdout的缓冲

Question

我正在使用管道从命令行可执行文件中获取重定向的stdout输出。不幸的是，在完成该过程之前，我没有得到任何输出。可执行文件在运行时输出进度状态，这就是我要解析的内容。

BOOL RunCmd( char  *pCmd, 
             char  *pWorkingDir, 
             int    nWaitSecs, 
             BOOL   fRegImport, 
             DWORD *pdwExitCode )
{
  BOOL                fSuccess = TRUE;
  STARTUPINFO         si;
  PROCESS_INFORMATION pi;
  SECURITY_ATTRIBUTES sFileSecurity;
  ZeroMemory( &sFileSecurity, sizeof( sFileSecurity ) );
  sFileSecurity.nLength        = sizeof( sFileSecurity );
  sFileSecurity.bInheritHandle = TRUE;

  HANDLE hReadPipe  = NULL;
  HANDLE hWritePipe = NULL;

  fSuccess = CreatePipe( &hReadPipe, &hWritePipe, &sFileSecurity, 0 );
  SetHandleInformation( hReadPipe, HANDLE_FLAG_INHERIT, 0 ); 

  ZeroMemory( &si, sizeof(si) );
  ZeroMemory( &pi, sizeof(pi) );
  si.cb          = sizeof( si );
  si.dwFlags     = STARTF_USESHOWWINDOW | STARTF_USESTDHANDLES;
  si.hStdOutput  = hWritePipe;
  si.hStdError   = hWritePipe;
  si.wShowWindow = SW_HIDE;

  int rc;

  // Start the child process. 
  rc = CreateProcess( NULL, // No module name (use command line). 
                      pCmd, // Command line. 
                      NULL,             // Process handle not inheritable. 
                      NULL,             // Thread handle not inheritable. 
                      TRUE,
                      CREATE_NO_WINDOW,
                      NULL,             // Use parent's environment block. 
                      pWorkingDir,      // Working folder
                      &si,              // Pointer to STARTUPINFO structure.
                      &pi );            // Pointer to PROCESS_INFORMATION structure.


  if( ! rc )
    return FALSE;

  // Wait until child process exits.
  DWORD dwWaitResult;
  DWORD dwTimeStart = ::GetTickCount();
  DWORD dwTimeNow;

  #define BUFSIZE 4096  

  DWORD dwRead = 0; 
  DWORD dwAvail;
  CHAR  chBuf[ BUFSIZE ];
  BOOL  bSuccess = TRUE;

  for( ;; )
  {
    dwTimeNow    = ::GetTickCount();
    dwWaitResult = ::WaitForSingleObject( pi.hProcess, ONE_SECOND );
    dwRead       = 0;

    for( dwAvail = 0; PeekNamedPipe( hReadPipe, 0, 0, 0, &dwAvail, 0 ) && dwAvail; dwAvail = 0 )
    {
      dwRead = 0;
      ReadFile( hReadPipe, chBuf, min( BUFSIZE, dwAvail ), &dwRead, NULL );

      if( dwRead > 0 )
      {
        FILE *op = fopen( "c:\REDIR.OUT", "a" );

        if( op )
        {
          fwrite( chBuf, 1, dwRead, op );
          fclose( op );
        }
      }
    }

    if( dwWaitResult == WAIT_OBJECT_0 )
    {
      DWORD dwExitCode;
      GetExitCodeProcess( pi.hProcess, &dwExitCode );

      if( pdwExitCode )
        (*pdwExitCode) = dwExitCode;

      break;
    }

    if( dwWaitResult == WAIT_TIMEOUT )
    {
      if( dwTimeNow - dwTimeStart < (DWORD)( ONE_SECOND * nWaitSecs ) )
        continue;
      else
      {
        fSuccess = FALSE;
        break;
      }
    }

    fSuccess = FALSE;
    break;
  }

  CloseHandle( pi.hProcess );
  CloseHandle( pi.hThread );
  CloseHandle( hReadPipe );
  CloseHandle( hWritePipe );

  return fSuccess;
}

每秒调用PeekNamedPipe（）调用，每次调用dwAvail为零，直到进程完成。

如何更快地从过程中获得输出？从控制台运行进程时，我看到进度输出。该过程将在其输出中使用“ r”以在同一行的开头显示百分比。