Can one executable be both a console and GUI appli

Question

I want to make a C# program that can be run as a CLI or GUI application depending on what flags are passed into it. Can this be done?

I have found these related questions, but they don't exactly cover my situation:

• How to write to the console in a GUI application
• How do I get console output in C++ with a Windows program?

Answer 1

/*
** dual.c    Runs as both CONSOLE and GUI app in Windows.
**
** This solution is based on the "Momentary Flicker" solution that Robert Kennedy
** discusses in the highest-rated answer (as of Jan 2013), i.e. the one drawback
** is that the console window will briefly flash up when run as a GUI.  If you
** want to avoid this, you can create a shortcut to the executable and tell the
** short cut to run minimized.  That will minimize the console window (which then
** immediately quits), but not the GUI window.  If you want the GUI window to
** also run minimized, you have to also put -minimized on the command line.
**
** Tested under MinGW:  gcc -o dual.exe dual.c -lgdi32
**
*/
#include <windows.h>
#include <stdio.h>

static int my_win_main(HINSTANCE hInstance,int argc,char *argv[],int iCmdShow);
static LRESULT CALLBACK WndProc(HWND hwnd,UINT iMsg,WPARAM wParam,LPARAM lParam);
static int win_started_from_console(void);
static BOOL CALLBACK find_win_by_procid(HWND hwnd,LPARAM lp);

int main(int argc,char *argv[])

    {
    HINSTANCE hinst;
    int i,gui,relaunch,minimized,started_from_console;

    /*
    ** If not run from command-line, or if run with "-gui" option, then GUI mode
    ** Otherwise, CONSOLE app.
    */
    started_from_console = win_started_from_console();
    gui = !started_from_console;
    relaunch=0;
    minimized=0;
    /*
    ** Check command options for forced GUI and/or re-launch
    */
    for (i=1;i<argc;i++)
        {
        if (!strcmp(argv[i],"-minimized"))
            minimized=1;
        if (!strcmp(argv[i],"-gui"))
            gui=1;
        if (!strcmp(argv[i],"-gui-"))
            gui=0;
        if (!strcmp(argv[i],"-relaunch"))
            relaunch=1;
        }
    if (!gui && !relaunch)
        {
        /* RUN AS CONSOLE APP */
        printf("Console app only.\n");
        printf("Usage:  dual [-gui[-]] [-minimized].\n\n");
        if (!started_from_console)
            {
            char buf[16];
            printf("Press <Enter> to exit.\n");
            fgets(buf,15,stdin);
            }
        return(0);
        }

    /* GUI mode */
    /*
    ** If started from CONSOLE, but want to run in GUI mode, need to re-launch
    ** application to completely separate it from the console that started it.
    **
    ** Technically, we don't have to re-launch if we are not started from
    ** a console to begin with, but by re-launching we can avoid the flicker of
    ** the console window when we start if we start from a shortcut which tells
    ** us to run minimized.
    **
    ** If the user puts "-minimized" on the command-line, then there's
    ** no point to re-launching when double-clicked.
    */
    if (!relaunch && (started_from_console || !minimized))
        {
        char exename[256];
        char buf[512];
        STARTUPINFO si;
        PROCESS_INFORMATION pi;

        GetStartupInfo(&si);
        GetModuleFileNameA(NULL,exename,255);
        sprintf(buf,"\"%s\" -relaunch",exename);
        for (i=1;i<argc;i++)
            {
            if (strlen(argv[i])+3+strlen(buf) > 511)
                break;
            sprintf(&buf[strlen(buf)]," \"%s\"",argv[i]);
            }
        memset(&pi,0,sizeof(PROCESS_INFORMATION));
        memset(&si,0,sizeof(STARTUPINFO));
        si.cb = sizeof(STARTUPINFO);
        si.dwX = 0; /* Ignored unless si.dwFlags |= STARTF_USEPOSITION */
        si.dwY = 0;
        si.dwXSize = 0; /* Ignored unless si.dwFlags |= STARTF_USESIZE */
        si.dwYSize = 0;
        si.dwFlags = STARTF_USESHOWWINDOW;
        si.wShowWindow = SW_SHOWNORMAL;
        /*
        ** Note that launching ourselves from a console will NOT create new console.
        */
        CreateProcess(exename,buf,0,0,1,DETACHED_PROCESS,0,NULL,&si,&pi);
        return(10); /* Re-launched return code */
        }
    /*
    ** GUI code starts here
    */
    hinst=GetModuleHandle(NULL);
    /* Free the console that we started with */
    FreeConsole();
    /* GUI call with functionality of WinMain */
    return(my_win_main(hinst,argc,argv,minimized ? SW_MINIMIZE : SW_SHOWNORMAL));
    }


static int my_win_main(HINSTANCE hInstance,int argc,char *argv[],int iCmdShow)

    {
    HWND        hwnd;
    MSG         msg;
    WNDCLASSEX  wndclass;
    static char *wintitle="GUI Window";

    wndclass.cbSize        = sizeof (wndclass) ;
    wndclass.style         = CS_HREDRAW | CS_VREDRAW;
    wndclass.lpfnWndProc   = WndProc;
    wndclass.cbClsExtra    = 0 ;
    wndclass.cbWndExtra    = 0 ;
    wndclass.hInstance     = hInstance;
    wndclass.hIcon         = NULL;
    wndclass.hCursor       = NULL;
    wndclass.hbrBackground = NULL;
    wndclass.lpszMenuName  = NULL;
    wndclass.lpszClassName = wintitle;
    wndclass.hIconSm       = NULL;
    RegisterClassEx (&wndclass) ;

    hwnd = CreateWindowEx(WS_EX_OVERLAPPEDWINDOW,wintitle,0,
                          WS_VISIBLE|WS_OVERLAPPEDWINDOW,
                          100,100,400,200,NULL,NULL,hInstance,NULL);
    SetWindowText(hwnd,wintitle);
    ShowWindow(hwnd,iCmdShow);
    while (GetMessage(&msg,NULL,0,0))
        {
        TranslateMessage(&msg);
        DispatchMessage(&msg);
        }
    return(msg.wParam);
    }


static LRESULT CALLBACK WndProc (HWND hwnd,UINT iMsg,WPARAM wParam,LPARAM lParam)

    {
    if (iMsg==WM_DESTROY)
        {
        PostQuitMessage(0);
        return(0);
        }
    return(DefWindowProc(hwnd,iMsg,wParam,lParam));
    }


static int fwbp_pid;
static int fwbp_count;
static int win_started_from_console(void)

    {
    fwbp_pid=GetCurrentProcessId();
    if (fwbp_pid==0)
        return(0);
    fwbp_count=0;
    EnumWindows((WNDENUMPROC)find_win_by_procid,0L);
    return(fwbp_count==0);
    }


static BOOL CALLBACK find_win_by_procid(HWND hwnd,LPARAM lp)

    {
    int pid;

    GetWindowThreadProcessId(hwnd,(LPDWORD)&pid);
    if (pid==fwbp_pid)
        fwbp_count++;
    return(TRUE);
    }

Answer 2

I have written up an alternative approach which avoids the console flash. See How to create a Windows program that works both as a GUI and console application.

Answer 3

I think the preferred technique is what Rob called the devenv technique of using two executables: a launcher ".com" and the original ".exe". This is not that tricky to use if you have the boilerplate code to work with (see below link).

The technique uses tricks to have that ".com" be a proxy for the stdin/stdout/stderr and launch the same-named .exe file. This give the behavior of allowing the program to preform in a command line mode when called form a console (potentially only when certain command-line arguments are detected) while still being able to launch as a GUI application free of a console.

I hosted a project called dualsubsystem on Google Code that updates an old codeguru solution of this technique and provides the source code and working example binaries.