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#
# Copyright 2013, Martin Owens <doctormo@gmail.com>
#
# This library is free software; you can redistribute it and/or
# modify it under the terms of the GNU Lesser General Public
# License as published by the Free Software Foundation; either
# version 3.0 of the License, or (at your option) any later version.
#
# This library is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
# Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public
# License along with this library.
#
"""
Access logs in known locations to find information about them.
"""
import os
import re
import codecs
from datetime import datetime
MATCHER = r'(?P<date>\w+ +\d+ +\d\d:\d\d:\d\d) (?P<host>\w+) ' + \
r'CRON\[(?P<pid>\d+)\]: \((?P<user>\w+)\) CMD \((?P<cmd>.*)\)'
class LogReader(object):
"""Opens a Log file, reading backwards and watching for changes"""
def __init__(self, filename, mass=4096):
self.filename = filename
self.mass = mass
self.size = -1
self.read = -1
self.pipe = None
def __enter__(self):
self.size = os.stat(self.filename)[6]
self.pipe = codecs.open(self.filename, 'r', encoding='utf-8')
return self
def __exit__(self, error_type, value, traceback):
self.pipe.close()
def __iter__(self):
if self.pipe is None:
with self as reader:
for (offset, line) in reader.readlines():
yield line
else:
for (offset, line) in self.readlines():
yield line
def readlines(self, until=0):
"""Iterator for reading lines from a file backwards"""
if not self.pipe or self.pipe.closed:
raise IOError("Can't readline, no opened file.")
# Always seek to the end of the file, this accounts for file updates
# that happen during our running process.
location = self.size
halfline = ''
while location > until:
location -= self.mass
mass = self.mass
if location < 0:
mass = self.mass + location
location = 0
self.pipe.seek(location)
line = self.pipe.read(mass) + halfline
data = line.split('\n')
if location != 0:
halfline = data.pop(0)
loc = location + mass
data.reverse()
for line in data:
if line.strip() == '':
continue
yield (loc, line)
loc -= len(line)
def cron_date_to_datetime(cron_str):
with_year = f"{cron_str} {datetime.now().year}"
return datetime.strptime(with_year, "%b %d %H:%M:%S %Y")
class CronLog(LogReader):
"""Use the LogReader to make a Cron specific log reader"""
def __init__(self, filename='/var/log/syslog', user=None):
LogReader.__init__(self, filename)
self.user = user
def for_program(self, command):
"""Return log entries for this specific command name"""
return ProgramLog(self, command)
def __iter__(self):
for line in super(CronLog, self).__iter__():
match = re.match(MATCHER, str(line))
datum = match and match.groupdict()
if datum and (not self.user or datum['user'] == self.user):
datum['date'] = cron_date_to_datetime(datum['date'])
yield datum
class ProgramLog(object):
"""Specific log control for a single command/program"""
def __init__(self, log, command):
self.log = log
self.command = command
def __iter__(self):
for entry in self.log:
if entry['cmd'] == str(self.command):
yield entry
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