How to avoid multiple instances of a program?

Question

I need to find a right way to prevent two running instances of my (Python) program. I am currently using the following method.

On Windows,

os.popen(\         


        

Answer 1

on Linux, I used to write a pidfile, roughly:

if (pidfile already exists)
    read pidfile content
    if (/proc//exec == my executable)
        already running, exit
    else
        it´s a stale pidfile, delete it
write my own pid to pidfile
start the 'real' work

lately, i´ve heard of the flock(1) tool. it´s easier to use in bash scripts:

( flock -n 200 || exit
    # ... commands executed under lock ...
) 200>/var/lock/mylockfile

and not too hard to use from 'real' programming languages, just open a file and try to get a flock(2) on it.