import time
import os
import sys

if len(sys.argv)!=2:
    print >> sys.stderr ,"Please specify filename to read"
filename = sys.argv[1]

if not os.path.isfile(filename):
    print >> sys.stderr ,"Given file: \"%s\" is not a file" % filename

with open(filename,‘r‘) as f:
    filesize = os.stat(filename)[6]
    f.seek(filesize)

    while True:
        where = f.tell()
        line = f.readline()
        if not line:
            time.sleep(where)
        else:
            print line

2.11 读取流数据源