C + + ensures that the program has only unique instances

Load the following function at the beginning of the program, such as in the initialization of the MFC program

//////////////////////////////////////////////////////////////////////////

Function Name: Program_mutex

Function: Ensure that only instances of the program are unique

Return value: 0-normal; 1-there is already a running instance;-1-Failed to create mutex object

//////////////////////////////////////////////////////////////////////////
int Program_mutex ()
{

HANDLE Hmutex = NULL;

TCHAR * lpszName = L "Appmutex";
int nret = 0;
Do
{

Hmutex =:: CreateMutex (Null,false,lpszname);

DWORD dwret =:: GetLastError ();

switch (dwret)

{

Case

0:

{

Break

;

}

case error_already_exists:

{

MessageBox (null,l" Notification: The application is already open.) \ n ", L" notice ", MB_OK);

nret = 1;

break;

}

default:

{

MessageBox (null,l" Hint: The application failed to create a mutex object. \ n ", L" error ", MB_OK);

nret =-1;

break;

}

}

} while (FALSE);
return nret;

}

C + + ensures that the program has only unique instances