I am writing a standard windows app in Delphi 7.
If I was writing a console app, I can call the following to output to the cmd line or output file.
writeln('Some info'); If I do this from my standard GUI app that I have started from the command line I get an error.
I/O Error 105 There must be a simple solution to this problem. Basically I want my app to have two modes, a GUI mode and a non-GUI mode. How do I set it up correctly so I can write back to the cmd window?
This question is very similar (if not exactly the same) as something I was trying to accomplish. I wanted to detect if my app was executed from a cmd.exe and send output to the parent console, otherwise it would display a gui. The answers here helped me solve my issue. Here is the code I came up with as an experiment:
ParentChecker.dpr
program ParentChecker; uses Vcl.Forms, SysUtils, PsAPI, Windows, TLHelp32, Main in 'Main.pas' {frmParentChecker}; {$R *.res} function AttachConsole(dwProcessID: Integer): Boolean; stdcall; external 'kernel32.dll'; function FreeConsole(): Boolean; stdcall; external 'kernel32.dll'; function GetParentProcessName(): String; const BufferSize = 4096; var HandleSnapShot: THandle; EntryParentProc: TProcessEntry32; CurrentProcessId: THandle; HandleParentProc: THandle; ParentProcessId: THandle; ParentProcessFound: Boolean; ParentProcPath: String; begin ParentProcessFound:=False; HandleSnapShot:=CreateToolhelp32Snapshot(TH32CS_SNAPPROCESS,0); if HandleSnapShot<>INVALID_HANDLE_VALUE then begin EntryParentProc.dwSize:=SizeOf(EntryParentProc); if Process32First(HandleSnapShot,EntryParentProc) then begin CurrentProcessId:=GetCurrentProcessId(); repeat if EntryParentProc.th32ProcessID=CurrentProcessId then begin ParentProcessId:=EntryParentProc.th32ParentProcessID; HandleParentProc:=OpenProcess(PROCESS_QUERY_INFORMATION or PROCESS_VM_READ,False,ParentProcessId); if HandleParentProc<>0 then begin ParentProcessFound:=True; SetLength(ParentProcPath,BufferSize); GetModuleFileNameEx(HandleParentProc,0,PChar(ParentProcPath),BufferSize); ParentProcPath:=PChar(ParentProcPath); CloseHandle(HandleParentProc); end; Break; end; until not Process32Next(HandleSnapShot,EntryParentProc); end; CloseHandle(HandleSnapShot); end; if ParentProcessFound then Result:=ParentProcPath else Result:=''; end; function IsPrime(n: Integer): Boolean; var i: Integer; begin Result:=False; if n<2 then Exit; Result:=True; if n=2 then Exit; i:=2; while i<(n div i + 1) do begin if (n mod i)=0 then begin Result:=False; Exit; end; Inc(i); end; end; var i: Integer; ParentName: String; begin ParentName:=GetParentProcessName().ToLower; Delete(ParentName,1,ParentName.LastIndexOf('\')+1); if ParentName='cmd.exe' then begin AttachConsole(-1); Writeln(''); for i:=1 to 100 do if IsPrime(i) then Writeln(IntToStr(i)+' is prime'); FreeConsole(); end else begin Application.Initialize; Application.MainFormOnTaskbar:=True; Application.CreateForm(TfrmParentChecker, frmParentChecker); frmParentChecker.Label1.Caption:='Executed from '+ParentName; Application.Run; end; end. Main.pas (form with label):
unit Main; interface uses Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics, Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, RzLabel; type TfrmParentChecker = class(TForm) Label1: TLabel; private { Private declarations } public { Public declarations } end; var frmParentChecker: TfrmParentChecker; implementation {$R *.dfm} end. This allows me to run my GUI app from a command prompt and display output to the same console where my app was launched. Otherwise, it will run the full GUI part of the app.
Example output from console window:
I:\Delphi\Tests and Demos\ParentChecker\Win32\Debug>start /wait ParentChecker.exe 2 is prime 3 is prime 5 is prime 7 is prime 11 is prime 13 is prime 17 is prime 19 is prime 23 is prime 29 is prime 31 is prime 37 is prime 41 is prime 43 is prime 47 is prime 53 is prime 59 is prime 61 is prime 67 is prime 71 is prime 73 is prime 79 is prime 83 is prime 89 is prime 97 is prime I:\Delphi\Tests and Demos\ParentChecker\Win32\Debug> Call AllocConsole to avoid the error 105.
I'm not quite sure what you are trying to achieve.
As I understood the question one way could be
program Project1; {$APPTYPE CONSOLE} uses Forms, Classes, Windows, Unit1 in 'Unit1.pas' { Form1 } ; {$R *.res} var Finished: Boolean; Input: String; function IsConsoleMode(): Boolean; var SI: TStartupInfo; begin SI.cb := SizeOf(TStartupInfo); GetStartupInfo(SI); Result := ((SI.dwFlags and STARTF_USESHOWWINDOW) = 0); end; procedure HandleInput; begin Finished := Input = 'quit'; if not Finished then begin Writeln('Echo: ' + Input); end else Writeln('Bye'); end; begin if IsConsoleMode then begin Finished := false; Writeln('Welcome to console mode'); while not Finished do begin readln(Input); HandleInput; end; end else begin Writeln('Entering GUI Mode'); FreeConsole; Application.Initialize; Application.MainFormOnTaskbar := True; Application.CreateForm(TForm1, Form1); Application.Run; end; end. There's no reliable way for a GUI subsystem application to attach to the console of its parent process. If you try to do so you end up with two active processes sharing the same console. This leads to no end of trouble.
The alternative, whilst retaining just a single executable, as suggested by bummi, is to have a console app that frees its console if it is asked to run in GUI mode. This is a better approach, but leads to a console window flashing up, and then closing, when you want to run in GUI mode.
The best discussion of the subject that I have come across on Stack Overflow is Rob Kennedy's superb answer: Can one executable be both a console and GUI application?
I believe, from what you say in comments, that the best option for you is to create two separate executables. One for the GUI subsystem, and one for the console subsystem. This is the approach taken by:
Yes you have to ship multiple executables. But doing so gives the user the best experience.
FWIW, I played around with this problem and happened upon AttachConsole which seems to do the trick. The only problem I ran into with my code is that the program won't give the console up without an extra ENTER key or two. It's not real polished since I was trying to fix that problem and (kind of) gave up. Perhaps someone here will see it?
program writecon; uses windows, dialogs; function AttachConsole(dwProcessID: DWord): BOOL; stdcall; external 'kernel32.dll'; function load_attach_console: boolean; begin Result := AttachConsole(-1); end; begin // the function requires XP or greater, you might want to check for that here. if load_attach_console = true then begin writeln; writeln('This is running in the console.'); write('Press ENTER to continue.'); readln; // from the linked page, you have to detach yourself from the console // when you're done, this is probably where the problem is. Flush(Output); Flush(Input); FreeConsole; end else MessageDlg('This is not running in the console.', mtInformation, [mbOk], 0); end. AttachConsole does seem to work, as noted above it waits for ENTER.
However, the program is still a win prog and not a console program as far as dos sees it, and so cmd proceeds to the next command after launching it.
test.exe & dir shows the dir listing first, then the output from test.exe
start /w test.exe & dir does work, and does not pause for ENTER key
BTW, the suggestion above: PostMessage(GetCurrentProcess,$0101,$0D,0); does the ENTER but is giving a bong noise.
I found this very complete article about the whole issue: http://www.boku.ru/2016/02/28/posting-to-console-from-gui-app/
I made a unit to do the AttachConsole, hook the exception handler to mirror messages to console.
To use it, you only need to call ATTACH in your code. It is best to make attaching a commandline option e.g -console
if FindCmdLineSwitch('console',true) then AttachConsole(true,true); This is for a gui application, and when using this, you must use START /W to launch your program is you expect it to be blocking on the commandline/batch e.g. start /w myprogram.exe -console
One handy benefit is that you can launch it standalone with a console if you want, and get to see all the error messages in the console.
unit ConsoleConnector; // Connects the/a console to a GUI program // Can hook exception handler to mirror messages to console. // To use it, you only need to call ATTACH // best to make attaching a commandline option e.g -console // if FindCmdLineSwitch('console',true) then AttachConsole(true,true); // When using this, you will use START to launch your program e.g. // start /w myprogram.exe -console // creates Console var at end in initialise/finalise - you might want to do this explicitly in your own program instead. // see: http://www.boku.ru/2016/02/28/posting-to-console-from-gui-app/ //sjb 18Nov16 interface uses sysutils,forms; type TConsoleConnector = class private OldExceptionEvent:TExceptionEvent; Hooked:boolean; BlockApplicationExceptionHandler:boolean; //errors ONLY to console, no error messageboxes blocking program procedure DetachErrorHandler; procedure GlobalExceptionHandler(Sender: TObject; E: Exception); procedure HookExceptionHandler; public IsAttached:boolean; function Attach( CreateIfNeeded:boolean=true; //Call ALLOCCONSOLE if no console to attach to HookExceptions:boolean=false; //Hook Application.OnException to echo all unhandled exceptions to console OnlyToConsole:boolean=false // Suppresses exception popups in gui, errors only go to console ):boolean; procedure Detach; //detach and unhook procedure writeln(S:string); //only writes if console is attached procedure ShowMessage(S:string); //Popup ShowMessage box and mirror to console. Obeys OnlyToConsole end; var Console:TConsoleConnector; implementation uses Windows,dialogs; //winapi function function AttachConsole(dwProcessId: Int32): boolean; stdcall; external kernel32 name 'AttachConsole'; function TConsoleConnector.Attach(CreateIfNeeded:boolean=true;HookExceptions:boolean=false;OnlyToConsole:boolean=false):boolean; begin IsAttached:=AttachConsole(-1); if not IsAttached and CreateIfNeeded then begin IsAttached:=AllocConsole; end; result:=IsAttached; if HookExceptions then HookExceptionHandler; end; procedure TConsoleConnector.Detach; begin FreeConsole; IsAttached:=false; DetachErrorHandler; end; procedure TConsoleConnector.WriteLn(S:string); begin if IsAttached then system.writeln(S); end; procedure TConsoleConnector.ShowMessage(S:string); begin self.Writeln(S); if BlockApplicationExceptionHandler then exit; dialogs.ShowMessage(S); end; procedure TConsoleConnector.GlobalExceptionHandler(Sender: TObject; E: Exception); begin self.Writeln(E.Message); if BlockApplicationExceptionHandler then exit; if assigned(OldExceptionEvent) //i.e there was an old event before we hooked it then OldExceptionEvent(Sender,E) else Application.ShowException(E); end; procedure TConsoleConnector.HookExceptionHandler; begin OldExceptionEvent:=Application.OnException; Application.OnException:=GlobalExceptionHandler; Hooked:=true; end; procedure TConsoleConnector.DetachErrorHandler; begin if Hooked //I have hooked it then begin Application.OnException:=OldExceptionEvent; OldExceptionEvent:=nil; Hooked:=false; end; end; initialization Console:=TconsoleConnector.create; finalization Console.Detach; Console.Destroy; end.