tail.py

'''
Basic tail command implementation
Usage:

tail.py filename numlines

'''

import sys
import linecache

if len(sys.argv) !=3:
    print 'Usage: tail.py <file> <nlines>'
    sys.exit(1)

# filename and number of lines requested
fname, nlines = sys.argv[1:]
nlines = int(nlines)

# count the total number of lines
tot_lines = len(open(fname).readlines())

# use line cache module to read the lines
for i in range(tot_lines - nlines + 1, tot_lines+1):
    print linecache.getline(sys.argv[1],i),

tail_2.py

""" This is a more efficient version, since it does not read the entire
file
"""

import sys
import os


lines = int(sys.argv[1])
if lines == 0:
    sys.exit('')

fname = sys.argv[2]
fsize = os.stat(fname).st_size

bufsize = 80

iter = 0
with open(sys.argv[2]) as f:
    if bufsize > fsize:
        bufsize = fsize - 1
    data = []
    while True:
        iter += 1
        offset = max(0, fsize - bufsize * iter)
        f.seek(offset)
        if offset == 0:
            print ''.join(f.readlines())
            break
        data = f.readlines()
        if len(data) > lines or f.tell() == 0:
            print(''.join(data[-lines:]))
            break