How to detect already running application...

["Freddie Unpenstein" <fredderic excite com>]

Hello peoples of the net...

I was wondering, if anyone has come across any reliable means to find an already running instance of your 
application, and get it to present itself instead of starting a new one.

I've done it in a small program I rolled together quickly, by creating a pid file in /tmp.  If the file 
exists and contains a number, it attempts to send a SIGUSR1 to the pid contained therein and then quits.  If 
not, it starts like usual.  On reciept of a SIGUSR1, the program simply does a gtk_window_present() on its 
main window.

This does have issues...  For one, if the process doesn't close down properly, the pid file will remain, and 
after some time a new process may well exist with the same pid, and the default handler for SIGUSR1 is to 
kill the process.  And secondly, my creation of the pid file isn't without a few race conditions.  While it's 
not a highly critical application, I would like to know if there's a safer and more reliable method of doing 
this.


Fredderic

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