""" Copyright (c) 2015 Ad Schellevis All rights reserved. Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met: 1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. 2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution. THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. """ import os def reverse_log_reader(filename, block_size=8192, start_pos=None): """ read log file in reverse order :param filename: filename to parse :param block_size: max block size to examine per loop :param start_pos: start at position in file (None is end of file) :return: generator """ with open(filename, 'rU') as f_in: if start_pos is None: f_in.seek(0, os.SEEK_END) file_byte_start = f_in.tell() else: file_byte_start = start_pos data = '' while True: if file_byte_start - block_size < 0: block_size = file_byte_start file_byte_start = 0 else: file_byte_start -= block_size f_in.seek(file_byte_start) data = f_in.read(block_size) + data eol = data.rfind('\n') while eol > -1: line_end = file_byte_start + len(data) line = data[eol:] data = data[:eol] eol = data.rfind('\n') # field line and position in file yield {'line': line.strip(), 'pos': line_end} if file_byte_start == 0 and eol == -1: # flush last line yield {'line': data.strip(), 'pos': len(data)} if file_byte_start == 0: break