import commands
import os
class singleinstance(object):
'''
singleinstance - based on Windows version by Dragan Jovelic this is a Linux
version that accomplishes the same task: make sure that
only a single instance of an application is running.
'''
def __init__(self, pidPath):
'''
pidPath - full path/filename where pid for running application is to be
stored. Often this is ./var/<pgmname>.pid
'''
self.pidPath=pidPath
#
# See if pidFile exists
#
if os.path.exists(pidPath):
#
# Make sure it is not a "stale" pidFile
#
pid=open(pidPath, 'r').read().strip()
#
# Check list of running pids, if not running it is stale so
# overwrite
#
pidRunning=commands.getoutput('ls /proc | grep %s' % pid)
if pidRunning:
self.lasterror=True
else:
self.lasterror=False
else:
self.lasterror=False
if not self.lasterror:
#
# Write my pid into pidFile to keep multiple copies of program from
# running.
#
fp=open(pidPath, 'w')
fp.write(str(os.getpid()))
fp.close()
def alreadyrunning(self):
return self.lasterror
def __del__(self):
if not self.lasterror:
os.unlink(self.pidPath)
if __name__ == "__main__":
#
# do this at beginnig of your application
#
myapp = singleinstance()
#
# check is another instance of same program running
#
if myapp.alreadyrunning():
sys.exit("Another instance of this program is already running")
#
# not running, safe to continue...
#
print "No another instance is running, can continue here"
