Hi,
Can anyone tell me how to check for open programs? For example, at the start of my program I would like to check if there is another instance of my program running. Does anyone know how to do that? Thanks.
Printable View
Hi,
Can anyone tell me how to check for open programs? For example, at the start of my program I would like to check if there is another instance of my program running. Does anyone know how to do that? Thanks.
You could probably use findwindow and set the code up before window creation, though there's probably better methods of doing it.
Code:HWND find;
find = FindWindow(NULL, "MyWindow name");
if (find) // or try find !=NULL
{
MessageBox(NULL,"hey, you're already using this program!",
"Error",MB_TOPMOST);
return 0;
}
Put this at the start of your program.
That will work even if there is a different program running that has the same window name as you.Code:CreateMutex(NULL, FALSE, "MYPROGRAMNAME");
if (GetLastError() == ERROR_ALREADY_EXISTS)
return 1;
Thanks for the help. However, would this work even if the program was hidden? (For example, if it was doing work in the background). By hidden I mean in the taskbar, but with no display window.
The one i posted will. It can even be a console program (doesnt have to have any window at all).
As 39ster has said, create a mutex -- See MSDN (http://msdn2.microsoft.com/en-us/lib...11(VS.85).aspx)
Don't forget to free the mutex when you're done, not that it matters -- it is good practice.
I only want to add that you should not restrict users to run your program several times unless absolutely necessary.
Many, I think (including me), get incredibly annoyed just because I can't open another instance because the program says I can't. Who is to decide here? Me or the application?
I always use an approach that gives the user full control, but perhaps warns a bit if it might be dangerous.
As a programmer, it seems cool to do things like everyone else does. Stop a program from running multiple instances, a nice splash screen, credits, etc. But the user does not enjoy those.
Ponder on that one.
You think you can run several windows Messagers on the same comp?
Or several programs that should start listening on one "well-known" port?
Or several programs that should open the same COM-port to configure the external device?
But that should, really, be restricted by the single resource that those two apps would require to use. I could for example run a terminal program using COM1, and another one using COM2. Or two different messenger applications using different ports, two mail servers using individual ports, etc, etc. Obviously, if I try to use COM1 from two different apps, I definitely would like to know about it - but that should be the case even if I try to use both teraterm and hyperterminal on COM1, not only if I try to use two instances of teraterm or hyperterminal. And the OS is quite competent on telling you if the resource is busy in these cases, so it shouldn't be a problem.Quote:
Originally Posted by vart
There are a few instances where there is no resource that prevents the app from running, where you still want to ensure that the same app is not running - in which case an "invented" resource such as a Mutex or other named object could be used (lock-files are the common way to do this in a portable way - instance 1 creates a file, instance 2 tries to creat the same file, and fails because instance 1 got there first).
--
Mats
Yes, it's possible with "Messenger Plus!".Quote:
Originally Posted by vart
And there's no saying you have to lock it to the same port.
And btw, even if it can't use the resource such as the COM port, it can still, if reasonable, allow its other features to be used.
I agree, however if the application was doing some large task it would be bad to have more than one open.Quote:
Originally Posted by Elysia
But that's not up to the program to decide; it's up to the user to decide.
No, that's partly the responsibility of the programmer to decide if running multiple instances of the program would cause woes to the end-user. Who knows the software better than the author? If there are valid reasons to prevent multiple instances from being launched, by all means, preventing it is smart programming.
I have a hard time finding a reason to ever do that. And if you do, a nice error message describing why to the user might also be nice.
Well, my dial-up software does this (yea, I'm cheap and still use it!) and it makes complete sense. Since the port is open and in use, what good would launching another instance of the dialer do? Nada. Saves an old fool like me from receiving an annoying alert-box telling me that my modem is already in use (which I had received a few times anyways when the window was minimized and I simply forget I was already signed on).
This may be a lousy example, but as you say, there probably isn't many valid examples out there.
...And if you had two modems (to add to your silly example)?
Thanks for the help everyone!
Wow, this kind of got stuck in the middle of an argument...
What's silly about the example? That my dialup software refuses to be relaunched while in use? What the hell good would it do to have two modems and only one phone line?Quote:
Originally Posted by Elysia
You were the one who claimed it was a lousy example, so... Maybe I should've referred to it as "lousy" then.
And who says you're limited to one phone line?
Holy Christ, it was just an example, Elysia. You asked for one, I gave you one, lousy in my own words, though valid none-the-less.
Let's leave it at that. It doesn't merit further discussion -
I was merely countering your belief that you should limit the program to one instance. No harsh feelings.
Even if you can think of very good reasons to do so, other users will probably do something you never imagined and get annoyed because you limit the instances. So my advice is: don't limit your applications to a single instance.
Users can see perfectly fine that your application is running (most of the time), so you don't really have to limit it.
I agree, it is rather annoying when applications tell me that I can only have one instance. Who better knows the software than the programmer? Few to none, but you tell me, does the programmer know every use of their software or do you think that at times people come up with innovative ways to use software.