#!/usr/bin/python
# -*- coding: utf-8 -*-
 
import ftplib
import os
import socket
 
HOST = 'ftp.mozilla.org'
DIRN = 'pub/mozilla.org/webtools'
FILE = 'bugzilla-3.6.9-to-3.6.10-nodocs.diff.gz'
 
def writedata(data):
    f = open(FILE,'wb')
    try:
        f.write(data)
    finally:
        f.close()
 
def main():
    try:
        f = ftplib.FTP(HOST)
    except (socket.error, socket.gaierror):
        print 'ERROR:cannot reach " %s"' % HOST
        return
    print '***Connected to host "%s"' % HOST
 
    try:
        f.login()
    except ftplib.error_perm:
        print 'ERROR: cannot login anonymously'
        f.quit()
        return
    print '*** Logged in as "anonymously"'
 
    try:
        f.cwd(DIRN)
    except ftplib.error_perm:
        print 'ERRORL cannot CD to "%s"' % DIRN
        f.quit()
        return
    print '*** Changed to "%s" folder' % DIRN
 
    try:
        #传一个回调函数给retrbinary() 它在每接收一个二进制数据时都会被调用
        f.retrbinary('RETR %s' %FILE, writedata)
    except ftplib.error_perm:
        print 'ERROR: cannot read file "%s"' %FILE
        os.unlink(FILE)
    else:
        print '*** Downloaded "%s" to CWD' % FILE
     
    f.quit()
    return
 
if __name__ == '__main__':
    main()