How to call a program has existed?

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Hi All:

I added the following code in OnInitDialog() to let the program do the thing which is:
it can't open the same program when the program has executed!

C++

BOOL COneInstanceDlg::OnInitDialog()
{
	CDialog::OnInitDialog();

	SetIcon(m_hIcon, TRUE);		
	SetIcon(m_hIcon, FALSE);		


	HANDLE hMutex;
	hMutex=CreateMutex(NULL,true,_T("Test program"));
	if(hMutex)
	{
		if(ERROR_ALREADY_EXISTS==GetLastError())
		{
		    //MessageBox(_T("The program has executed"),MB_OK);
		    ExitProcess(0); //close program
		}
	}
	return TRUE;
}

But if I wanna do the next step:
The program has executed when you open it again,
and it will call and show the ex-program you have opened.

How can I do?

Thanks a lot!!

Posted 3-Mar-14 23:30pm

Member 10307999

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Leo Chapiro · Answer 1 · 2014-03-04T00:11:00

I think you don't use Mutex correctly, take a look at the documentation: http://msdn.microsoft.com/en-us/library/windows/desktop/ms682411%28v=vs.85%29.aspx[^]

Return value
If the function succeeds, the return value is a handle to the newly created mutex object.
If the function fails, the return value is NULL. To get extended error information, call GetLastError

.

That means you need something like this:

C++

BOOL COneInstanceDlg::OnInitDialog()
{
	...	
 
	HANDLE hMutex;
	hMutex=CreateMutex(NULL,true,_T("Test program"));
	if(NULL == hMutex)
	{
		if(ERROR_ALREADY_EXISTS==GetLastError())
		{
		    //MessageBox(_T("The program has executed"),MB_OK);
		    ExitProcess(0); //close program
		}
	}

	return TRUE;
}

P.S.: Apart of this I would make m_hMutex a member variable of your COneInstanceDlg class to have the chance to release the mutex after your program exits.