python 锁
#!/usr/bin/env python#!coding=utf-8
#锁定操作
import socket , traceback , os, sys, fcntl, time
import signal
#fcntl
"""
flock(FH,LOCK_EX|LOCK_SH|LOCK_UN)
LOCK_EX 独占锁，排他锁
LOCK_SH 共享锁
LOCK_UN 对文件解锁
"""
def getlastaccess(fd , ip):
fcntl.flock(fd, fcntl.LOCK_SH) #
try:
fd.seek(0)
for line in fd.readlines():
fileip , assesstime = line.strip().split("|")
if fileip == ip:
return assesstime
return None
finally:
print"in getlastaccess finally"
fcntl.flock(fd, fcntl.LOCK_UN) #解除锁，释放锁
def writelastaccess(fd, ip):
print fcntl.flock(fd, fcntl.LOCK_EX)
records = []
try:
fd.seek(0)
for line in fd.readlines():
fileip , accesstime = line.strip().split("|")
if fileip!=ip:
records.append((fileip,accesstime))
fd.seek(0)
for fileip , accesstime in records + [(ip , time.asctime())]:
fd.write("%s|%s\n" %(fileip, accesstime))
fd.truncate()
finally:
print "in writelastaccess finally "
fcntl.flock(fd, fcntl.LOCK_UN)
def reap(signum , stackframe):
while 1:
try:
result = os.waitpid(-1, os.WNOHANG)
if not result:
break
except:
break
print "reaped child process %d"%(result)
host=''
port = 9002
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
s.bind((host, port))
s.listen(1)
fd = open("lastaccess.txt", "w+")
while 1:
try:
clientsock, clientaddr = s.accept()
except KeyboardInterrupt:
raise
except:
traceback.print_exc()
continue
signal.signal(signal.SIGCHLD, reap)
pid = os.fork()
if pid:
clientsock.close()
continue
else:
s.close()
try:
print "got connection from %s ,servicing with pid %d"%\
(clientsock.getpeername(), os.getpid())
ip = clientsock.getpeername()
clientsock.sendall("welcome ,%s \n" % ip)
last = getlastaccess(fd, ip)
if last:
clientsock.sendall("i last saw you at %s.\n" %last)
else:
clientsock.sendall("i've never seen you before.\n")
writelastaccess(fd, ip)
clientsock.sendall("i have noted your connection at %s.n"%\
getlastaccess(fd, ip))
except (KeyboardInterrupt, SystemExit):
raise
except:
traceback.print_exc()
#time.sleep(10)
try:
clientsock.close()
except KeyboardInterrupt:
raise
except:
traceback.print_exc()
sys.exit()
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