Caesar Wang wrote:
> Hello:
>
> I've developed one MFC program.
> But the OS reboot each time i open the program twice and then close
> them.
> The program runs normally when only one program being opened each
> time.
>
> How can i stop opening the program when the program is opened?
> (How to detect program running in MFC? )
>
>
> thanks for your help ^^
>
>
>
>
>

Make a nice long unique name, that only your program knows, and attempt
to create a mutex using that name. The result tells you whether such a
mutex already exists.

BOOL CSomeApp::InitInstance()
{
// Exit if another instance of this program is running.
m_hMutex = CreateMutex(NULL, TRUE, "unique string");
if (!m_hMutex || GetLastError() == ERROR_ALREADY_EXISTS)
{ if (m_hMutex)
{ ReleaseMutex(m_hMutex);
CloseHandle(m_hMutex);
}
return FALSE; // this instance exits
}

....also remember to do the CloseHandle stuff in ExitInstance.


--
Scott McPhillips [VC++ MVP]

> Make a nice long unique name, that only your program knows, and attempt
> to create a mutex using that name. The result tells you whether such a
> mutex already exists.
>
> BOOL CSomeApp::InitInstance()
> {
> // Exit if another instance of this program is running.
> m_hMutex = CreateMutex(NULL, TRUE, "unique string");
> if (!m_hMutex || GetLastError() == ERROR_ALREADY_EXISTS)
> { if (m_hMutex)
> { ReleaseMutex(m_hMutex);
> CloseHandle(m_hMutex);
> }
> return FALSE; // this instance exits
> }
>
> ...also remember to do the CloseHandle stuff in ExitInstance.

Just a question about a minor point: Why do you call ReleaseMutex
only if GetLastError() == ERROR_ALREADY_EXISTS?
IMO then you should get another error: ERROR_NOT_OWNER
Shouldn't ReleaseMutex been called when the first instance starts?
Something like

BOOL CSomeApp::InitInstance()
{
// Exit if another instance of this program is running.
m_hMutex = CreateMutex(NULL, TRUE, "unique string");
DWORD dwError = GetLastError();

if (m_hMutex != NULL && dwError != ERROR_ALREADY_EXISTS)
ReleaseMutex(m_hMutex);

if (m_hMutex == NULL || dwError == ERROR_ALREADY_EXISTS)
return FALSE;

...

return TRUE;
}

BOOL CSomeApp::ExitInstance()
{
if (m_hMutex != NULL)
CloseHandle(m_hMutex);

return CWinApp::ExitInstance();
}

Uwe Kotyczka wrote:

>>Make a nice long unique name, that only your program knows, and attempt
>>to create a mutex using that name. The result tells you whether such a
>>mutex already exists.
>>
>>BOOL CSomeApp::InitInstance()
>>{
>> // Exit if another instance of this program is running.
>> m_hMutex = CreateMutex(NULL, TRUE, "unique string");
>> if (!m_hMutex || GetLastError() == ERROR_ALREADY_EXISTS)
>> { if (m_hMutex)
>> { ReleaseMutex(m_hMutex);
>> CloseHandle(m_hMutex);
>> }
>> return FALSE; // this instance exits
>> }
>>
>>...also remember to do the CloseHandle stuff in ExitInstance.
>
>
> Just a question about a minor point: Why do you call ReleaseMutex
> only if GetLastError() == ERROR_ALREADY_EXISTS?
> IMO then you should get another error: ERROR_NOT_OWNER
> Shouldn't ReleaseMutex been called when the first instance starts?
> Something like
>
> BOOL CSomeApp::InitInstance()
> {
> // Exit if another instance of this program is running.
> m_hMutex = CreateMutex(NULL, TRUE, "unique string");
> DWORD dwError = GetLastError();
>
> if (m_hMutex != NULL && dwError != ERROR_ALREADY_EXISTS)
> ReleaseMutex(m_hMutex);
>
> if (m_hMutex == NULL || dwError == ERROR_ALREADY_EXISTS)
> return FALSE;
>
> ...
>
> return TRUE;
> }
>
> BOOL CSomeApp::ExitInstance()
> {
> if (m_hMutex != NULL)
> CloseHandle(m_hMutex);
>
> return CWinApp::ExitInstance();
> }

I don't remember why I acquire the mutex ownership. Something that
might have helped in a situation long ago, when a service and security
were involved (I think). It is probably overkill and your observation
seems correct.

--
Scott McPhillips [VC++ MVP]

"Caesar Wang" wrote in message news:...
> Hello:
>
> I've developed one MFC program.
> But the OS reboot each time i open the program twice and then close
> them.
> The program runs normally when only one program being opened each
> time.
>
> How can i stop opening the program when the program is opened?
> (How to detect program running in MFC? )
>
>
> thanks for your help ^^

Hi, just look for the class "CWinAppEx" in www.codeproject.com"