--- /dev/null
+#!/usr/bin/env python
+
+'''
+Python-Tail - Unix tail follow implementation in Python.
+
+python-tail can be used to monitor changes to a file.
+
+Example:
+ import tail
+
+ # Create a tail instance
+ t = tail.Tail('file-to-be-followed')
+
+ # Register a callback function to be called when a new line is found in the followed file.
+ # If no callback function is registerd, new lines would be printed to standard out.
+ t.register_callback(callback_function)
+
+ # Follow the file with 5 seconds as sleep time between iterations.
+ # If sleep time is not provided 1 second is used as the default time.
+ t.follow(s=5) '''
+
+# Author - Kasun Herath <kasunh01 at gmail.com>
+# Source - https://github.com/kasun/python-tail
+
+# modified by Hans-Christoph Steiner <hans@eds.org> to add the
+# background thread and support reading multiple lines per read cycle
+
+import os
+import sys
+import time
+import threading
+
+
+class Tail(object):
+ ''' Represents a tail command. '''
+ def __init__(self, tailed_file):
+ ''' Initiate a Tail instance.
+ Check for file validity, assigns callback function to standard out.
+
+ Arguments:
+ tailed_file - File to be followed. '''
+
+ self.check_file_validity(tailed_file)
+ self.tailed_file = tailed_file
+ self.callback = sys.stdout.write
+ self.t_stop = threading.Event()
+
+ def start(self, s=1):
+ '''Start tailing a file in a background thread.
+
+ Arguments:
+ s - Number of seconds to wait between each iteration; Defaults to 3.
+ '''
+
+ t = threading.Thread(target=self.follow, args=(s,))
+ t.start()
+
+ def stop(self):
+ '''Stop a background tail.
+ '''
+ self.t_stop.set()
+
+ def follow(self, s=1):
+ ''' Do a tail follow. If a callback function is registered it is called with every new line.
+ Else printed to standard out.
+
+ Arguments:
+ s - Number of seconds to wait between each iteration; Defaults to 1. '''
+
+ with open(self.tailed_file, encoding='utf8') as file_:
+ # Go to the end of file
+ file_.seek(0, 2)
+ while not self.t_stop.is_set():
+ curr_position = file_.tell()
+ lines = file_.readlines()
+ if len(lines) == 0:
+ file_.seek(curr_position)
+ else:
+ for line in lines:
+ self.callback(line)
+ time.sleep(s)
+
+ def register_callback(self, func):
+ ''' Overrides default callback function to provided function. '''
+ self.callback = func
+
+ def check_file_validity(self, file_):
+ ''' Check whether the a given file exists, readable and is a file '''
+ if not os.access(file_, os.F_OK):
+ raise TailError("File '%s' does not exist" % (file_))
+ if not os.access(file_, os.R_OK):
+ raise TailError("File '%s' not readable" % (file_))
+ if os.path.isdir(file_):
+ raise TailError("File '%s' is a directory" % (file_))
+
+
+class TailError(Exception):
+
+ def __init__(self, msg):
+ self.message = msg
+
+ def __str__(self):
+ return self.message