import sys
import os
try:
import fcntl
except ImportError:
fcntl = None
LOCK_PATH = os.path.join(os.path.abspath(os.path.dirname(sys.argv[0])), "lock")
OS_WIN = False
if 'win32' in sys.platform.lower():
OS_WIN = True
class SingleInstance:
def __init__(self):
self.fh = None
self.is_running = False
self.do_magic()
def do_magic(self):
if OS_WIN:
try:
if os.path.exists(LOCK_PATH):
os.unlink(LOCK_PATH)
self.fh = os.open(LOCK_PATH, os.O_CREAT | os.O_EXCL | os.O_RDWR)
except EnvironmentError as err:
if err.errno == 13:
self.is_running = True
else:
raise
else:
try:
self.fh = open(LOCK_PATH, 'w')
fcntl.lockf(self.fh, fcntl.LOCK_EX | fcntl.LOCK_NB)
except EnvironmentError as err:
if self.fh is not None:
self.is_running = True
else:
raise
def clean_up(self):
# this is not really needed
try:
if self.fh is not None:
if OS_WIN:
os.close(self.fh)
os.unlink(LOCK_PATH)
else:
fcntl.lockf(self.fh, fcntl.LOCK_UN)
self.fh.close() # ???
os.unlink(LOCK_PATH)
except Exception as err:
# logger.exception(err)
raise # for debugging porpuses, do not raise it on production
if __name__ == "__main__":
import time
si = SingleInstance()
try:
if si.is_running:
sys.exit("This app is already running!")
time.sleep(20) # remove
# do other stuff
finally:
si.clean_up()
