Question

I want to get access to the buffer of another process console (via AttachConsole), for calling ReadConsoleOutput, etc.

Is a DOS 16bit application. I can’t use pipes because it doesn’t writes output secuentially (it emulates “windows”.. like FAR commander if you know what I mean).

So I should:

1) launch the app
2) get the process id
3) call AttachConsole(ProcId)
4) call GetConsoleScreenBufferInfo to get the size
5) call ReadConsoleOutput

The problem is at 3: when I call AttachConsole ir returns 0, and after a call to GetLastError it reports ERROR_INVALID_PARAMETER 87 (0x57).

The only parameter of AttachConsole is the ProcessId and I’ve checked it with ProcessExplorer that is right (it’s actually the PID of ntvdm.exe that emulates the app).

Delphi code:

function AttachConsole(dwProcessId: DWORD): Cardinal; external kernel32 name 'AttachConsole';

var
  Handle: HWND;

function EnumWindowsProc(hwnd: HWND; lParam: LPARAM): BOOL; stdcall;
var
  s: string;
  IsVisible, IsOwned, IsAppWindow: Boolean;
begin
  Result := True;//carry on enumerating

  IsVisible := IsWindowVisible(hwnd);
  if not IsVisible then
    exit;

  IsOwned := GetWindow(hwnd, GW_OWNER)<>0;
  if IsOwned then
    exit;

  IsAppWindow := GetWindowLongPtr(hwnd, GWL_STYLE) and WS_EX_APPWINDOW<>0;
  if not IsAppWindow then
    exit;

  SetLength(s, GetWindowTextLength(hwnd));
  GetWindowText(hwnd, PChar(s), Length(s)+1);
  if AnsiContainsText(s, '????.EXE') then // set windows name to search
    Handle := hwnd;
end;

procedure Test(Strings: TStrings);
var
  ProcessID: Cardinal;
begin
  Handle := 0;
  EnumWindows(@EnumWindowsProc, 0);
  Strings.Add('Handle: ' + IntToStr(Handle));
  if Handle <> 0 then
    SetForegroundWindow(Handle);
  Sleep(100);

  GetWindowThreadProcessId(Handle, @ProcessID);
  Strings.Add('ProcessId: ' + IntToStr(ProcessID));

  if AttachConsole(ProcessId) <> 0 then
    Strings.Add('Ok Attached')
  else
    Strings.Add('Error: ' + IntToStr(GetLastError));
end;

Drop memo and button in form. At OnClick call Test(Memo1.Lines).

===== EDIT complete solution =====

function AttachAndGetConsoleHandle(ProcessId: Cardinal): Cardinal;
begin
  if not AttachConsole(ProcessId) then
    raise Exception.Create('AttachConsole error: ' + IntToStr(GetLastError));

  Result := GetStdHandle(STD_OUTPUT_HANDLE);

  if Result = INVALID_HANDLE_VALUE then
    raise Exception.Create('GetStdHandle(STD_OUTPUT_HANDLE) error: ' + IntToStr(GetLastError));
end;

procedure DettachConsole;
begin
  if not FreeConsole then
    raise Exception.Create('FreeConsole error: ' + IntToStr(GetLastError));
end;

function ReadConsole(ConsoleHandle: Cardinal): TStringList;
var
  BufferInfo: _CONSOLE_SCREEN_BUFFER_INFO;
  BufferSize, BufferCoord: _COORD;
  ReadRegion: _SMALL_RECT;
  Buffer: Array of _CHAR_INFO;
  I, J: Integer;
  Line: AnsiString;
begin
  Result := TStringList.Create;

  ZeroMemory(@BufferInfo, SizeOf(BufferInfo));
  if not GetConsoleScreenBufferInfo(ConsoleHandle, BufferInfo) then
    raise Exception.Create('GetConsoleScreenBufferInfo error: ' + IntToStr(GetLastError));

  SetLength(Buffer, BufferInfo.dwSize.X * BufferInfo.dwSize.Y);

  BufferSize.X := BufferInfo.dwSize.X;
  BufferSize.Y := BufferInfo.dwSize.Y;
  BufferCoord.X := 0;
  BufferCoord.Y := 0;
  ReadRegion.Left := 0;
  ReadRegion.Top := 0;
  ReadRegion.Right := BufferInfo.dwSize.X;
  ReadRegion.Bottom := BufferInfo.dwSize.Y;

  if ReadConsoleOutput(ConsoleHandle, Pointer(Buffer), BufferSize, BufferCoord, ReadRegion) then
  begin
    for I := 0 to BufferInfo.dwSize.Y - 1 do
    begin
      Line := '';
      for J := 0 to BufferInfo.dwSize.X - 1 do
        Line := Line + Buffer[I * BufferInfo.dwSize.X + J].AsciiChar;
      Result.Add(Line)
    end
  end
  else
    raise Exception.Create('ReadConsoleOutput error: ' + IntToStr(GetLastError));
end;

Answer 1

The definition should be:

function AttachConsole(dwProcessId: DWORD): BOOL; stdcall; external
kernel32 name 'AttachConsole';

So the code following it should be:

if AttachConsole(ProcessId) then

Can’t help you anymore than that.