Question and Answer Database
FAQ1769C.txt Using a Mutex to check for previous instances
Category :Windows API
Platform :All
Product :C++Builder 1.x
Question:
How do I check if there is a previous instance
of my application running?
Answer:
Among the many ways that have been used to do this, using a
mutex is probably the easiest. The following code illistrates
how to use a Mutex to do this.
HANDLE CheckForPrevious (const char *MutexName){
//try to create the mutex
HANDLE Mutex = CreateMutex (NULL, true, MutexName);
//check if we where allowed to create the mutex
//if we where not allowed to do this then return 0
//saying that there is a previous instance of the program
int nResult = GetLastError ();
if (!nResult)
return 0;
//if it was create return the Mutex Handle
else
return Mutex;
}
you can use this function at the start of an app to see if the
app is already running like so:
...
Handle Mutex = CheckForPrevious (MutexName);
if (!Mutex){
MessageBox (NULL, "Previous instance of the application running",
"Previous Instance", MB_OK | MB_ICONEXCLAMATION);
return 1;
}
...
7/2/98 10:32:32 AM
Last Modified: 01-SEP-99