import time
import sys

from typing import Callable, NoReturn


class Tail(object):
    def __init__(
            self,
            file_name: str,
            output: Callable[[str], NoReturn] = sys.stdout.write,
            interval: int = 1
    ):
        self.file_name: str = file_name
        self.output: Callable[[str], NoReturn] = output
        self.interval: int = interval

    def __call__(self):
        with open(self.file_name) as f:
            f.seek(0, 2)  # 從文件結(jié)尾處開(kāi)始seek
            while True:
                line: str = f.readline()
                if line:
                    self.output(line)  # 使用print都會(huì)每次都打印新的一行
                else:
                    time.sleep(self.interval)


if __name__ == '__main__':
    filename: str = sys.argv[0]
    Tail(filename)()

import time
import sys

from typing import Callable, NoReturn


class Tail(object):
    def __init__(
            self,
            file_name: str,
            output: Callable[[str], NoReturn] = sys.stdout.write,
            interval: int = 1
    ):
        self.file_name: str = file_name
        self.output: Callable[[str], NoReturn] = output
        self.interval: int = interval

    def __call__(self):
        with open(self.file_name) as f:
            self.read_last_line(f)
            while True:
                line: str = f.readline()
                if line:
                    self.output(line)  # 使用print都會(huì)每次都打印新的一行
                else:
                    time.sleep(self.interval)

    def read_last_line(self, f):
        last_lines = f.readlines()[-10:]
        for line in last_lines:
            self.output(line)

if __name__ == '__main__':
    filename: str = sys.argv[0]
    Tail(filename)()   

import time
import sys

from typing import Callable, List, NoReturn


class Tail(object):
    def __init__(
            self,
            file_name: str,
            output: Callable[[str], NoReturn] = sys.stdout.write,
            interval: int = 1,
            len_line: int = 1024
    ):
        self.file_name: str = file_name
        self.output: Callable[[str], NoReturn] = output
        self.interval: int = interval
        self.len_line: int = len_line

    def __call__(self, n: int = 10):
        with open(self.file_name) as f:
            self.read_last_line(f, n)
            while True:
                line: str = f.readline()
                if line:
                    self.output(line)  # 使用print都會(huì)每次都打印新的一行
                else:
                    time.sleep(self.interval)

    def read_last_line(self, file, n):
        read_len: int = self.len_line * n

        # 跳轉(zhuǎn)游標(biāo)到最后
        file.seek(0, 2)
        # 獲取當(dāng)前結(jié)尾的游標(biāo)位置
        now_tell: int = file.tell()
        while True:
            if read_len > file.tell():
                # 如果跳轉(zhuǎn)的字符長(zhǎng)度大于原來(lái)文件長(zhǎng)度,那就把所有文件內(nèi)容打印出來(lái)
                file.seek(0) # 由于read方法是按照游標(biāo)進(jìn)行打印, 所以要重置游標(biāo)
                last_line_list: List[str] = file.read().split('\n')[-n:]
                # 重新獲取游標(biāo)位置
                now_tell: int = file.tell()
                break
            # 跳轉(zhuǎn)到我們預(yù)估的字符位置
            file.seek(-read_len, 2)
            read_str: str = file.read(read_len)
            cnt: int = read_str.count('\n')
            if cnt >= n:
                # 如果獲取的行數(shù)大于要求的行數(shù),則獲取前n行的行數(shù)
                last_line_list: List[str] = read_str.split('\n')[-n:]
                break
            else:
                # 如果獲取的行數(shù)小于要求的行數(shù),則預(yù)估需要獲取的行數(shù),繼續(xù)獲取
                if cnt == 0:
                    line_per: int = read_len
                else:
                    line_per: int = int(read_len / cnt)
                read_len = line_per * n

        for line in last_line_list:
            self.output(line + '\n')
        # 重置游標(biāo),確保接下來(lái)打印的數(shù)據(jù)不重復(fù)
        file.seek(now_tell)


if __name__ == '__main__':
    import argparse

    parser = argparse.ArgumentParser()
    parser.add_argument("-f", "--filename")
    parser.add_argument("-n", "--num", default=10)
    args, unknown = parser.parse_known_args()
    if not args.filename:
        raise RuntimeError('filename args error')
    Tail(args.filename)(int(args.num))

import os
import sys

from typing import Callable, List, NoReturn

import pyinotify

multi_event = pyinotify.IN_MODIFY | pyinotify.IN_MOVE_SELF  # 監(jiān)控多個(gè)事件


class InotifyEventHandler(pyinotify.ProcessEvent):  # 定制化事件處理類，注意繼承
    """
    執(zhí)行inotify event的封裝
    """
    f: 'open()'
    filename: str
    path: str
    wm: 'pyinotify.WatchManager'
    output: Callable

    def my_init(self, **kargs):
        """pyinotify.ProcessEvent要求不能直接繼承__init__, 而是要重寫my_init, 我們重寫這一段并進(jìn)行初始化"""

        # 獲取文件
        filename: str = kargs.pop('filename')
        if not os.path.exists(filename):
            raise RuntimeError('Not Found filename')
        if '/' not in filename:
            filename = os.getcwd() + '/' + filename
        index = filename.rfind('/')
        if index == len(filename) - 1 or index == -1:
            raise RuntimeError('Not a legal path')

        self.f = None
        self.filename = filename
        self.output: Callable = kargs.pop('output')
        self.wm = kargs.pop('wm')
        # 只監(jiān)控路徑,這樣就能知道文件是否移動(dòng)
        self.path = filename[:index]
        self.wm.add_watch(self.path, multi_event)

    def read_line(self):
        """統(tǒng)一的輸出方法"""
        for line in self.f.readlines():
            self.output(line)

    def process_IN_MODIFY(self, event):
        """必須為process_事件名稱，event表示事件對(duì)象, 這里表示監(jiān)控到文件發(fā)生變化, 進(jìn)行文件讀取"""
        if event.pathname == self.filename:
            self.read_line()

    def process_IN_MOVE_SELF(self, event):
        """必須為process_事件名稱，event表示事件對(duì)象, 這里表示監(jiān)控到文件發(fā)生重新打開(kāi), 進(jìn)行文件讀取"""
        if event.pathname == self.filename:
            # 檢測(cè)到文件被移動(dòng)重新打開(kāi)文件
            self.f.close()
            self.f = open(self.filename)
            self.read_line()

    def __enter__(self) -> 'InotifyEventHandler':
        self.f = open(self.filename)
        return self

    def __exit__(self, exc_type, exc_val, exc_tb):
        self.f.close()


class Tail(object):
    def __init__(
            self,
            file_name: str,
            output: Callable[[str], NoReturn] = sys.stdout.write,
            interval: int = 1,
            len_line: int = 1024
    ):
        self.file_name: str = file_name
        self.output: Callable[[str], NoReturn] = output
        self.interval: int = interval
        self.len_line: int = len_line

        wm = pyinotify.WatchManager()  # 創(chuàng)建WatchManager對(duì)象
        inotify_event_handler = InotifyEventHandler(
            **dict(filename=file_name, wm=wm, output=output)
        )  # 實(shí)例化我們定制化后的事件處理類, 采用**dict傳參數(shù)
        wm.add_watch('/tmp', multi_event)  # 添加監(jiān)控的目錄，及事件
        self.notifier = pyinotify.Notifier(wm, inotify_event_handler)  # 在notifier實(shí)例化時(shí)傳入,notifier會(huì)自動(dòng)執(zhí)行
        self.inotify_event_handle: 'InotifyEventHandler' = inotify_event_handler

    def __call__(self, n: int = 10):
        """通過(guò)inotify的with管理打開(kāi)文件"""
        with self.inotify_event_handle as i:
            # 先讀取指定的行數(shù)
            self.read_last_line(i.f, n)
            # 啟用inotify的監(jiān)聽(tīng)
            self.notifier.loop()

    def read_last_line(self, file, n):
        read_len: int = self.len_line * n

        # 獲取當(dāng)前結(jié)尾的游標(biāo)位置
        file.seek(0, 2)
        now_tell: int = file.tell()
        while True:
            if read_len > file.tell():
                # 如果跳轉(zhuǎn)的字符長(zhǎng)度大于原來(lái)文件長(zhǎng)度,那就把所有文件內(nèi)容打印出來(lái)
                file.seek(0)
                last_line_list: List[str] = file.read().split('\n')[-n:]
                # 重新獲取游標(biāo)位置
                now_tell: int = file.tell()
                break
            file.seek(-read_len, 2)
            read_str: str = file.read(read_len)
            cnt: int = read_str.count('\n')
            if cnt >= n:
                # 如果獲取的行數(shù)大于要求的行數(shù),則獲取前n行的行數(shù)
                last_line_list: List[str] = read_str.split('\n')[-n:]
                break
            else:
                # 如果獲取的行數(shù)小于要求的行數(shù),則預(yù)估需要獲取的行數(shù),繼續(xù)獲取
                if cnt == 0:
                    line_per: int = read_len
                else:
                    line_per: int = int(read_len / cnt)
                read_len = line_per * n

        for line in last_line_list:
            self.output(line + '\n')
        # 重置游標(biāo),確保接下來(lái)打印的數(shù)據(jù)不重復(fù)
        file.seek(now_tell)


if __name__ == '__main__':
    import argparse

    parser = argparse.ArgumentParser()
    parser.add_argument("-f", "--filename")
    parser.add_argument("-n", "--num", default=10)
    args, unknown = parser.parse_known_args()
    if not args.filename:
        raise RuntimeError('filename args error')
    Tail(args.filename)(int(args.num))