[Bill] >> Desktop to the executable). The problem is, only *one* person at a time >> should run the program. >
[Alan] > The usual way of doing this is simply to create an empty file > when the program starts and delete it when the program closes > In python: > > ############## > # File : exRun.py > ''' usage python exRun.py foo.exe > > prevents more than one copy of the guarded program running > ''' > > import os, sys > > if len(sys.argv) != 2: > print "Usage: python exRun.py <application name>" > sys.exit() > > prog = sys.argv[1] > fname = prog+'running.dat' > try: > open(fname,'w').close() # create an empty file. > os.system(prog) > os.remove(fname) > except IOError: > print prog, 'is already running, try again later' > sys.exit() > ################ Alan, Thank you for the code above . I'll take a look at it. Much shorter than my approach :-) [Bill] >> 4. If 'otherProg' is not running, start it and write to the config file >> that 'otherProg' is running (also write who is running it). >> 5. 'myProg' continues to run on the user's computer, continuously >> checking the PID (of 'otherProg') to see if the process is still alive. >> 6. When we don't find the PID anymore, write to the config file that >> 'otherProg' isn't running. >> 7. Shutdown 'myProg'. [Alan] > The design above will work too of course but uses more CPU cycles > and may be slightly harder to fix if the machine crashes while the app > is running sincve the open config file could be corrupted. My first attempt at continuously checking the PID was using a lot of CPU time. Then I added a sleep(.5) in my loop and the CPU % dropped to about 0% (at least according to Task Manager). [Bill] >> Now in step #3 above - if 'myProg' reads the config file and finds that >> the 'otherProg' is currently running, the user is warned that 'The >> program is currently in use by <insert username from config file>!' And >> 'otherProg' is not started. [Alan] > The current user name can be obtained from getpass.getuser() if you need > it. Yeah, my code uses that too. [Bill] >> 2. 'myProg.exe' and the config file live on the network in the same >> directory as 'otherProg'. [Alan] > There's no real need for that. My version usually lives in a common > area since it can be used to control multiple apps, and it usually writes > its file into a semi-hidden folder to avoid unscrupulous users deleting > the file!. I think I was just trying to make it easy for my program to find the program to start (since it'll look in the current directory first). I didn't want to hard-code any paths. But it looks like with your approach, I just issue the path to the executable on the command line and be done with it. Regarding the config file deletion - I've set the permissions on the .ini so that users can read & write to the file, but not delete it. But certainly a user with Admin privs could still delete it. Also , if my program doesn't find the .ini file - it creates a new one (although it must be setup again). [Bill] >> BTW, I've never stopped to consider if there was a simple 'Windows >> networking / permissions' type solution to the problem. I just went >> straight to Python :-) [Alan] > You can do it all using DOS style BAT files if you use my approach. I just knew someone would come up with an easier way :-) Thanks again, Alan! I'll play around with the code you posted. Bill _______________________________________________ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
