Re: [Lazarus] writeln to stdout in windows?

[Henry Vermaak]

2008/7/29 Seth Grover <[EMAIL PROTECTED]>:
> hm. if i compile with -WC, then it opens up a separate console window
> (even though I also have "windows gui application", -WG, checked) and
> the writeln goes to that console window.
>
> that's not what i want, though... if i run from the command line, i
> want to see the messages written to the console. if i just run the
> executable from the windows gui, i don't want to see a console, but i
> don't want the writeln's to raise an exception.

you can find out whether you program is run from the console by using
the GetStdHandle function.  it returns 0 if it's a gui app.

see: http://msdn.microsoft.com/en-us/library/ms683231(VS.85).aspx

it's tricky to do, but you can detect and attach to the console an app
is run from, but you can't use writeln.  look at this code (not tested
on fpc):

program guiconsole;

uses
  Forms, Windows, SysUtils,
  main in 'main.pas' {Form1};

{$R *.res}

const
  ATTACH_PARENT_PROCESS = DWORD(-1);

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


var
  h: THandle;
  dum: Cardinal;
  msg1: String = 'You''re running this from a command window!';

begin
      h := GetStdHandle(STD_OUTPUT_HANDLE);
      if h = 0
        then begin
          Application.Initialize;
          Application.CreateForm(TForm1, Form1);
          Application.Run;
        end
        else if h <> INVALID_HANDLE_VALUE
          then begin
            AttachConsole(ATTACH_PARENT_PROCESS);
            h := GetStdHandle(STD_OUTPUT_HANDLE);
            if (h = 0) or (h = INVALID_HANDLE_VALUE)
              then MessageBox(0, PChar(Format('GetStdHandle error!
%d', [h])), 'Error', MB_OK);
            sleep(1000);
            if not WriteConsole(h, pchar(msg1), length(msg1), dum, nil)
              then MessageBox(0, PChar(Format('WriteConsole error!
%d', [h])), 'Error', MB_OK);

{            AllocConsole();
            Writeln('You''re running this from a command window!'); }
          end
          else MessageBox(0, PChar(Format('GetStdHandle error! %d',
[h])), 'Error', MB_OK);
end.

using writeconsole is a pain, though.  i don't know if there's any way
of making fpc use the attached console as stdout.  i'll let you
experiment...

henry
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