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A New Twist On Is App Running
Message
General information
Forum:
Visual FoxPro
Category:
Windows API functions
Miscellaneous
Thread ID:
00409058
Message ID:
00409114
Views:
47
>I have an application that runs in the background. There is no user intervention via the application. One issue I have is people running the application more than one cause they cannot see it is running. I need to be able to detect the running app without using the Title bar as part of the solution. So I can just ignore someone trying to run it again.
>
>
>Any Ideas? George :)
>

I'm not George, but I like using the native Event object for the OS via a couple of API calls:
DECLARE INTEGER CreateEvent IN WIN32API ;
   INTEGER lpEventAttributes, ;
   SHORT bManualReset, ;
   SHORT bInitialState, ;
   STRING @ lpName
DECLARE INTEGER GetLastError IN Win32API
DECLARE CloseHandle IN Win32API INTEGER hObject
nEh = CreateEvent(0,0,1, PROGRAM(0) + '.EVENT')
IF GetLastError() = 183 OR nEh = 0
   *  There's an instance running already (183) or the Event can't be defined
   *  So don't do it;  do release the handle, since it's harmless and should
   *  be done rather than relying on Windows to clean up after itself
   =CloseHandle(nEh)
   QUIT
ENDIF

*  While shutting down, issue:
=CloseHandle(nEh)
This has the advantage that it derives it's Event name from the executable, and if you do forget to issue a CloseHandle(), it still releases the Event object without bleeding, and the Event object completely disappears automagically when no remaining Event refs exist. CLOSE ALL will release the Event. You can use the Event for synchronizing several processes or thread using WaitForSingleObject() to wait on someone to 'raise' the event if you need some sort of event monitoring. Works under all OS versions I tested - not checked under Win95, but does work on Win98 and ME, as well as NT and 2K.

You can use any name you want if linking to the app's initial program doesn't work for you - I chose that because it's easy to get right, and presumably you want to block other instances of the app you're starting.
EMail: EdR@edrauh.com
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"No, the horizon is moving up!"
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NT and Win2K FAQ .. cWashington WSH/ADSI/WMI site
MS WSH site ........... WSH FAQ Site
Wrox Press .............. Win32 Scripting Journal
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