Multitasking operating systems (all modern operating systems) allow us to execute an applications then once at the same time and this is a great feature. But, in some special cases, you may want to allow only one instance application.

I needed a way for my Back In Time project so I searched on the internet and found a very simple solution: when the application start it looks for a file that contains the “application instance” pid. If the file exists and the pid (from this file) is still valid then the application is already running so this second instance must exit. If not the application can start and save it’s pid in this file.

This is my Python implentation (applicationinstance.py).

If you want to use it in your application, all you have to do is:

from applicationinstance import *
 
#create application instance
appInstance = ApplicationInstance( '/tmp/myapplication.pid' )
 
# ... execute your application
 
#remove pid file
appInstance.exitApplication()

Tags: Linux, python

This entry was posted on Thursday, October 30th, 2008 at 16:00 and is filed under Linux, Python/PyGTK, Tips, Tricks & Scripts. You can follow any responses to this entry through the feed. You can leave a response, or trackback from your own site.