#!/usr/bin/env python
import os
import sys
def get_last_n_lines(logfile, n):
blk_size_max = 4096
n_lines = []
with open(logfile, 'rb') as fp:
fp.seek(0, os.SEEK_END)
cur_pos = fp.tell()
while cur_pos > 0 and len(n_lines) < n:
blk_size = min(blk_size_max, cur_pos)
fp.seek(cur_pos - blk_size, os.SEEK_SET)
blk_data = fp.read(blk_size)
assert len(blk_data) == blk_size
lines = blk_data.split('\n')
# adjust cur_pos
if len(lines) > 1 and len(lines[0]) > 0:
n_lines[0:0] = lines[1:]
cur_pos -= (blk_size - len(lines[0]))
else:
n_lines[0:0] = lines
cur_pos -= blk_size
fp.seek(cur_pos, os.SEEK_SET)
if len(n_lines) > 0 and len(n_lines[-1]) == 0:
del n_lines[-1]
return n_lines[-n:]
def main():
if len(sys.argv) != 3:
sys.exit('usage: %s logfile n_lines' % sys.argv[0])
for line in get_last_n_lines(sys.argv[1], int(sys.argv[2])):
print line
if __name__ == '__main__':
main()
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