用python实现的类似tail的程序

tail.py

from mmap import mmap
def tail(fn, count=10):
    with open(fn,'r+') as f:
        data = mmap(f.fileno(), 0)
        pos = len(data)
        for _ in range(count):
            pos = data.rfind('\n', 0, pos)
            if pos == -1: 
                pos = 0
                break
        return data[pos:].split('\n')


#另外一种思路
import os

def tail(fn, n=1):
    '''返回文件fn中最后n行'''
    N, data = 1024, ''
    f = open(fn, 'rb')
    fsize = os.path.getsize(fn)

    f.seek(0, 2)
    for i in xrange(fsize-N, -N, -N):
        last_loc = f.tell()
        f.seek(max(i, 0))
        data = f.read(last_loc-f.tell()) + data
        if data.count('\n') > n:
            break
        f.seek(max(i, 0))

    lines = data.splitlines()[-n:]
    for line in lines:
        print line