用Python来实现<>

用Python来实现<>

    最近在学习python，又不知道写个什么来练手，就想到用python来实现<>里面的例程，



＜一＞  第二章，例2－3的清除函数：

#! /usr/bin/env python
# -*- coding:utf-8 -*-
#TO:
#BY:
#File: cleanup.py
#Date: 2008-00-12/26/08
#

import os
import sys

LOG_DIR="/var/log"
ROOT_UID=0
LINES=50
E_XCD=65
E_NOTROOT=67

if os.getuid() != ROOT_UID:
    print "Must be root to run this script."
    sys.exit(E_NOTROOT)

if len(sys.argv) != 1:
    lines=int(sys.argv[1])
else:
    lines=LINES

os.chdir(LOG_DIR)

if os.getcwd() != LOG_DIR:
    print "Can't change to %s" % LOG_DIR
    sys.exit(E_XCD)

fr = open("messages")
fw = open("mesg.temp","w")
s = fr.readlines()
num_of_lines = len(s)
for i in range((num_of_lines-lines),num_of_lines):
    fw.write(s[i])

fr.close()
fw.close()

os.rename("mesg.temp","messages")

fr = open("/dev/null")
fw = open("wtmp","w")
ss = fr.read()
fw.write(ss)

fr.close()
fw.close()

print "Logs cleaned up."

sys.exit(0)