sibiaoluo

read_file_backwards_buffer_regex.py

#!/usr/bin/python
#coding:utf-8

import re
import sys
import os

def filerev(somefile, buffer=256):
    somefile.seek(0, os.SEEK_END)
    size = somefile.tell()
    lines = ['']
    rem = size % buffer
    pos = max(0, (size // buffer - 1) * buffer)
    while pos >= 0:
        somefile.seek(pos, os.SEEK_SET)
        data = somefile.read(rem + buffer) + lines[0]
        rem = 0
        pos -= buffer
        lines = re.findall(r'[^\n]*\n?', data)
        ix = len(lines) - 2
        while ix > 0:
             yield lines[ix]
             ix -= 1
    else:
        yield lines[0]

with open(sys.argv[1], 'r') as f:
    for line in filerev(f):
        sys.stdout.write(line)