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参考代码：

'''
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

import os
import sys
import time

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

    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) as file_:
            # Go to the end of file
            file_.seek(0,2)
            while True:
                curr_position = file_.tell()
                line = file_.readline()
                if not line:
                    file_.seek(curr_position)
                else:
                    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

单文件引用示例（将上面的代码存为文件「tail.py」）：

import tail

# Create a tail instance
t = tail.Tail('tail_test.log')  #要监控的文件必须已经存在，否则会抛出异常

# 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)

t.follow()

更多参考链接：

• 实现Python版的tail -f功能
• Python 模拟 linux shell 下的 tail -f 动态打印日志
• Python动态监控日志的内容
• python实现tail（考虑到几种特殊情况）
  • http://www.cnblogs.com/bufferfly/p/4878688.html
  • http://www.the5fire.com/python-code-linux-tail.html
  • http://blog.sina.com.cn/s/blog_53bd284b0102vbh4.html
  • http://chenzhou123520.iteye.com/blog/1963341
• Python实现tail命令，包含-f -n参数

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