# Dual licensed under the MIT and GPL licenses.
import fcntl
import os
class PidFile(object):
"""Context manager that locks a pid file. Implemented as class
not generator because daemon.py is calling .__exit__() with no parameters
instead of the None, None, None specified by PEP-343."""
# pylint: disable=R0903
def __init__(self, path):
self.path = path
self.pidfile = None
def __enter__(self):
self.pidfile = open(self.path, "a+")
try:
fcntl.flock(self.pidfile.fileno(), fcntl.LOCK_EX | fcntl.LOCK_NB)
except IOError:
raise SystemExit("Already running according to " + self.path)
self.pidfile.seek(0)
self.pidfile.truncate()
self.pidfile.write(str(os.getpid()))
self.pidfile.flush()
self.pidfile.seek(0)
return self.pidfile
def __exit__(self, exc_type=None, exc_value=None, exc_tb=None):
try:
self.pidfile.close()
except IOError as err:
# ok if file was just closed elsewhere
if err.errno != 9:
raise
os.remove(self.path)
# example usage
import daemon
context = daemon.DaemonContext()
context.pidfile = PidFile("/var/run/mydaemon")
Diff to Previous Revision
--- revision 2 2011-10-17 12:44:04
+++ revision 3 2013-10-07 21:03:30
@@ -1,3 +1,5 @@
+# Dual licensed under the MIT and GPL licenses.
+
import fcntl
import os
