# tail.py
# Usage: python tail.py FILENAME LINES
# similar to linux command: tail -n LINES FILENAME
def last_lines(filename, lines = 1):
    """
    Print the last several line(s) of a text file.
    Argument filename is the name of the file to print.
    Argument lines is the number of lines to print from last.
    """
    lines = int(lines)
    block_size = 1024
    block = ''
    nl_count = 0
    start = 0
    fsock = file(filename, 'rU')
    try:
        # seek to end
        fsock.seek(0, 2)
        # get seek position
        curpos = fsock.tell()
        while(curpos > 0): #while not EOF
            # seek ahead block_size+the length of last read block
            curpos -= (block_size + len(block));
            if curpos < 0: 
                curpos = 0
            fsock.seek(curpos)
            # read to end
            block = fsock.read()
            nl_count = block.count('\n')
            # if read enough(more)
            if nl_count >= lines:
                break
        # get the exact start position
        for n in range(nl_count - lines + 1):
            start = block.find('\n', start) + 1
    finally:
        fsock.close()
    print block[start:]

if __name__ == '__main__':
    import sys
    last_lines(sys.argv[1], sys.argv[2])