winapi: CreateProcess but hide the process' window?

Question

I am using CreateProcess to create a cmd.exe process that is passed a parameter that it executes and quits, this makes command prompt flash up on the screen.

I tried to avoid this by setting STARTUPINFO struct wShowWindow to SW_HIDE but this parameter seems to affect the calling window, not the window for the process that gets executed.

Is there anyway that you can use createprocess to launch a program that is hidden from view?

Also what is the proper winapi standard way to get enviroment variables?

Solution 1

set the STARTF_USESHOWWINDOW in dwFlags

by sharptooth

Solution 2

If its just a console app you can also use the CREATE_NO_WINDOW flag as part of the CreateProcess call itself, e.g.

CreateProcess(NULL, lpszCommandLine, NULL, NULL, FALSE, 
              CREATE_NO_WINDOW, NULL, NULL, &si, &pi);

Also, see this page for information about environment variables.

Solution 3

The following link here describes how to create the window silently:

DWORD RunSilent(char* strFunct, char* strstrParams)
{
    STARTUPINFO StartupInfo;
    PROCESS_INFORMATION ProcessInfo;
    char Args[4096];
    char *pEnvCMD = NULL;
    char *pDefaultCMD = "CMD.EXE";
    ULONG rc;

    memset(&StartupInfo, 0, sizeof(StartupInfo));
    StartupInfo.cb = sizeof(STARTUPINFO);
    StartupInfo.dwFlags = STARTF_USESHOWWINDOW;
    StartupInfo.wShowWindow = SW_HIDE;

    Args[0] = 0;

    pEnvCMD = getenv("COMSPEC");

    if(pEnvCMD){

        strcpy(Args, pEnvCMD);
    }
    else{
        strcpy(Args, pDefaultCMD);
    }

    // "/c" option - Do the command then terminate the command window
    strcat(Args, " /c "); 
    //the application you would like to run from the command window
    strcat(Args, strFunct);  
    strcat(Args, " "); 
    //the parameters passed to the application being run from the command window.
    strcat(Args, strstrParams); 

    if (!CreateProcess( NULL, Args, NULL, NULL, FALSE,
        CREATE_NEW_CONSOLE, 
        NULL, 
        NULL,
        &StartupInfo,
        &ProcessInfo))
    {
        return GetLastError();      
    }

    WaitForSingleObject(ProcessInfo.hProcess, INFINITE);
    if(!GetExitCodeProcess(ProcessInfo.hProcess, &rc))
        rc = 0;

    CloseHandle(ProcessInfo.hThread);
    CloseHandle(ProcessInfo.hProcess);

    return rc;

}

I think getenv and setenv are all okay? I am not sure what you are asking about in that respect.

Comments

[ereOn]

+1: This is the correct way to do that. Useful when you need to call cscript from the session 0 but don't want any console to popup.

[Alex Bagnolini]

For future references: CREATE_NO_WINDOW has value &H8000000

[Anil8753]

How to launch UI application (win32/wpf) in hidden mode. I want to show it later, not at the time of launch.

[script'n'code]

For me it doesn't work. I still see a flashing CMD window: ghostbin.com/paste/xr7eo (same when using CREATE_NEW_CONSOLE in CreateProcess)

[John Zabroski]

Not bad, but strcat is unsafe, and getenv can return way more than 4096 characters. wiki.sei.cmu.edu/confluence/display/c/… Use strcat_s instead.