使用pyinotify实现加强版的linux tail -f 命令，并且对日志类型的文本进行单独优化着色显示。

tail -f命令不能自动切换切片文件，例如日志是每100M生成一个新文件，tail -f不能自动的切换文件，必须关闭然后重新运行tail -f

此篇使用pyinotify，检测文件更新，并实现tail -f以外，还能自动识别切换切片文件。而且针对日志类型的文件做了单独样式优化。

运行 ./tailf.py + 文件路径。

此文件够自动从普通文本中，对日志就行着色处理，如果不是日志类型的文件，将直接输出，不进行着色处理。

tailf.py文件的实现代码如下：

import os
import sys
import re
import pyinotify

DIRMASK = pyinotify.IN_MODIFY \
          | pyinotify.IN_ATTRIB \
          | pyinotify.IN_MOVE_SELF \
          | pyinotify.IN_CREATE

class Handler(pyinotify.ProcessEvent):

    def __init__(self, filename):
        self._fh = None
        self._path = filename

        super(Handler, self).__init__()

    def my_init(self):
        try:
            self._fh = open(self._path, 'r')
        except IOError as e:
            sys.stderr.write('open file failed, %s' % e)
        else:
            self._fh.seek(0, 2)

    def process_IN_CREATE(self, event):
        path = self._path

        if path in os.path.join(event.path, event.name):
            if hasattr(self, 'fh'):
                self._fh.close()

            try:
                self._fh = open(self._path, 'r')
            except IOError as e:
                sys.stderr.write('open file failed, %s' % e)
            else:
                self._fh.seek(0, 2)

                for r in self._fh.readlines():
                    # sys.stdout.write(r)
                    process_line(r)

    def process_IN_MODIFY(self, event):
        path = self._path

        if path not in os.path.join(event.path, event.name):
            return

        if not self._fh.closed:
            for r in self._fh.readlines():
                # sys.stdout.write(r)
                process_line(r)

    def process_IN_MOVE_SELF(self, event):
        path = self._path

        if path in os.path.join(event.path, event.name):
            sys.stderr.write('monitor file move')

    def process_IN_ATTRIB(self, event):
        pass

class Tailer(object):

    def __init__(self, filename):
        super(Tailer, self).__init__()
        self._path = filename
        self._notifier = None

        self._init()

    def __del__(self):
        self._notifier.stop()

    def _init(self):
        path = self._path

        index = path.rfind('/')
        wm = pyinotify.WatchManager()
        wm.add_watch(path[:index], DIRMASK)

        handler = Handler(path)
        self._notifier = pyinotify.Notifier(wm, handler)

    def run(self):
        self.read_last_10240_word()
        while True:
            self._notifier.process_events()

            if self._notifier.check_events():
                self._notifier.read_events()

    def read_last_10240_word(self):
        with open(self._path,'rb') as f:
            f.seek(-10240,2)
            for l in f.readlines():
                # print(l.decode())
                process_line(l.decode())

def process_line(line_str):
    pass
    #matcher = re.search(r'\d{4}-\d{2}-\d{2}.*?- (DEBUG|INFO|WARNING|ERROR|CRITICAL) -[\s\S]*?(File ".*?.py", line \d*)', line_str)
    matcher = re.search(r'^\d{4}-\d{2}-\d{2}.*?(DEBUG|INFO|WARNING|ERROR|CRITICAL)', line_str)
    if not matcher:
        print(line_str)
    else:
        log_level_str = matcher.group(1)
        if log_level_str == 'DEBUG':
            print('\033[0;32m%s\033[0m' % line_str)
        elif log_level_str == 'INFO':
            print('\033[0;96m%s\033[0m' % line_str)
        elif log_level_str == 'WARNING':
            print('\033[0;33m%s\033[0m' % line_str)
        elif log_level_str == 'ERROR':
            print('\033[0;35m%s\033[0m' % line_str)
        elif log_level_str == 'CRITICAL':
            print('\033[0;31m%s\033[0m' % line_str)

if __name__ == '__main__':
    if len(sys.argv[1:]) != 1:
        print('Usage: python tail.py </path/to/filename>')
        sys.exit(0)

    path = sys.argv[1]
    Tailer(path).run()