tail

 

#!/usr/bin/env python

import optparse
import os
import sys
import time

class Error(Exception): pass
class FileError(Error): pass

class Tail(object):

    def __init__(self, path, sleep=1.0, reopen_count=5):
        self.path = path
        self.sleep = sleep
        self.reopen_count = reopen_count

    def __iter__(self):
        while True:
            pos = self.file.tell()
            line = self.file.readline()
            if not line:
                self.wait(pos)
            else:
                yield line

    def open(self, tail=True):
        try:
            self.real_path = os.path.realpath(self.path)
            self.inode = os.stat(self.path).st_ino
        except OSError, error:
            raise FileError(error)
        try:
            self.file = open(self.real_path)
        except IOError, error:
            raise FileError(error)
        if tail:
            self.file.seek(0, 2)

    def close(self):
        try:
            self.file.close()
        except Exception:
            pass

    def reopen(self):
        self.close()
        reopen_count = self.reopen_count
        while reopen_count >= 0:
            reopen_count -= 1
            try:
                self.open(tail=False)
                return True
            except FileError:
                time.sleep(self.sleep)
        return False

    def check(self, pos):
        try:
            if self.real_path != os.path.realpath(self.path):
                return True
            stat = os.stat(self.path)
            if self.inode != stat.st_ino:
                return True
            if pos > stat.st_size:
                return True
        except OSError:
            return True
        return False

    def wait(self, pos):
        if self.check(pos):
            if not self.reopen():
                raise Error('Unable to reopen file: %s' % self.path)
        else:
            self.file.seek(pos)
            time.sleep(self.sleep)