detect two instances of our program

[anand123]

Friends is there any way to detect two instances of our program executing.I mean multiple instances of the application running so that i could prompt a message to the user

[anand123]

i got it


// app.h
class CYourApp : public CWinApp
{
...

private:
HANDLE hMutex;
};

// app.cpp
BOOL CYourApp::InitInstance()
{
// Create mutex
hMutex = ::CreateMutex(NULL, TRUE, "GlobalMutex");

switch(::GetLastError())
{
case ERROR_SUCCESS:
// Mutex created successfully. There is no instance running
break;

case ERROR_ALREADY_EXISTS:
// Mutex already exists so there is a running instance of our app.
return FALSE;

default:
// Failed to create mutex by unknown reason
return FALSE;
}
}



i got the code from previous faq

[SOCM_FP_CPP]

hi ,

what will happen , if another program resort to the same technique ?
(with mutex name "GlobalMutex" )
why one cannot use GUIDs for this ? any thoughts ?

Praseed Pai

[DRZ]

HANDLE hdl;
hdl = CreateMutex(NULL, TRUE, "MyTestMutex");
if(hdl)
{
DWORD dwRetCode = GetLastError();
if(dwRetCode == ERROR_ALREADY_EXISTS)
{
AfxMessageBox("Another instance is already running@!!!");
return FALSE;
}
}

[cilu]

hi ,

what will happen , if another program resort to the same technique ?
(with mutex name "GlobalMutex" )
why one cannot use GUIDs for this ? any thoughts ?

Praseed Pai

The FAQ presents a simple technique to achive the goal. Of course "GlobalMutex" is not a very good name. You can come with something like "GlobalMutex@ProgramName#Author@Year". I doubt that you'll have two indentical identifiers...

[Hokutata]

... or better use GUIDGEN.EXE provided with Visual C++ to generate a unique string as for example "{3690872D-DAB2-4243-B5F8-1832567BC25E}".

[Andreas Masur]

Take a look at the following FAQ...

[anand123]

but this is not working in vc.net ,its working in vc++ only

[SOCM_FP_CPP]

Hi anand ,

It seems that ur writing a managed application using VC.NET. if ur trying to write unmanged ( win32 console or Win32 gui ) code , the above scheme should work.

Praseed Pai

[Andreas Masur]

but this is not working in vc.net ,its working in vc++ only

What do you mean with "it not working in vc.net"? This will work disregarding whether it is .NET or not in the first place...