Prof-Bloodstone/index.html

## index.html
<!DOCTYPE html>
<html>
<head>
	<meta charset="utf-8">
	<meta http-equiv="X-UA-Compatible" content="IE=edge">
	<title>Tail </title>
	<style>
		body {font-family: monospace;}
		p{ margin: 0;}
		ul{padding: 0;}
		li{list-style:none; padding: 0; margin: 0;}
	</style>
</head>
<body>
<ul id="logger">

</ul>
<script>
	const socket = new WebSocket('ws://localhost:9000');
	var log = document.getElementById('logger')

  	// Listen for messages
	socket.addEventListener('message', function (event) {
		var text = document.createTextNode(event.data)
		var li = document.createElement("li")
		li.appendChild(text)
		log.prepend(li)
	});
</script>

</body>
</html>

## tail.py
"""
We need websockets

    pip install websockets

Run both servers:

    python tail.py webserver /var/log/syslog
    python tail.py tailserver /var/log/syslog

Go to http://127.0.0.1:8000

Test in linux by:

    logger "this is a message"

"""
import sys
import asyncio
import websockets

from wsgiref.simple_server import make_server

loop = asyncio.get_event_loop()
options = {}


def line_offsets(file):
    """Seeks line offsets from file"""
    start_loc = file.tell()
    try:
        file.seek(0)
        # Read in the file once and build a list of line offsets
        line_offset = []
        offset = 0
        for line in file:
            line_offset.append(offset)
            offset += len(line)

        return line_offset
    finally:
        file.seek(start_loc)  # Come back to the same spot

async def tail(websocket, path):
    with open(options['path'], 'rt') as file:
        seek = line_offsets(file)[-20]
        sleep = None

        while True:
            file.seek(seek)
            line = file.readline()
            where = file.tell()

            if line:
                if seek != where:
                    sleep = None
                    await websocket.send(line.strip())
            else:
                sleep = 0.04

            seek = where

            if sleep:
                await asyncio.sleep(sleep)


def wsgiapplication(environ, start_response):
    start_response('200 OK', [('Content-Type', 'text/html')])
    return open('index.html', 'rb')


def main(action):
    if action == 'webserver':
        with make_server('', 8000, wsgiapplication) as httpd:
            print("Serving on port 8000...")

            try:
                httpd.serve_forever()
            except KeyboardInterrupt:
                httpd.shutdown()

    elif action == 'tailserver':
        tail_server = websockets.serve(tail, '', 9000)
        loop.run_until_complete(tail_server)
        loop.run_forever()


if __name__ == '__main__':
    assert len(sys.argv) == 3, "Required at least two arguments, action and log path."

    _, action, path = sys.argv

    options['path'] = path

    main(action)
	<!DOCTYPE html>
	<html>
	<head>
	<meta charset="utf-8">
	<meta http-equiv="X-UA-Compatible" content="IE=edge">
	<title>Tail </title>
	<style>
	body {font-family: monospace;}
	p{ margin: 0;}
	ul{padding: 0;}
	li{list-style:none; padding: 0; margin: 0;}
	</style>
	</head>
	<body>
	<ul id="logger">

	</ul>
	<script>
	const socket = new WebSocket('ws://localhost:9000');
	var log = document.getElementById('logger')

	// Listen for messages
	socket.addEventListener('message', function (event) {
	var text = document.createTextNode(event.data)
	var li = document.createElement("li")
	li.appendChild(text)
	log.prepend(li)
	});
	</script>

	</body>
	</html>
	"""
	We need websockets

	pip install websockets

	Run both servers:

	python tail.py webserver /var/log/syslog
	python tail.py tailserver /var/log/syslog

	Go to http://127.0.0.1:8000

	Test in linux by:

	logger "this is a message"

	"""
	import sys
	import asyncio
	import websockets

	from wsgiref.simple_server import make_server

	loop = asyncio.get_event_loop()
	options = {}


	def line_offsets(file):
	"""Seeks line offsets from file"""
	start_loc = file.tell()
	try:
	file.seek(0)
	# Read in the file once and build a list of line offsets
	line_offset = []
	offset = 0
	for line in file:
	line_offset.append(offset)
	offset += len(line)

	return line_offset
	finally:
	file.seek(start_loc) # Come back to the same spot

	async def tail(websocket, path):
	with open(options['path'], 'rt') as file:
	seek = line_offsets(file)[-20]
	sleep = None

	while True:
	file.seek(seek)
	line = file.readline()
	where = file.tell()

	if line:
	if seek != where:
	sleep = None
	await websocket.send(line.strip())
	else:
	sleep = 0.04

	seek = where

	if sleep:
	await asyncio.sleep(sleep)


	def wsgiapplication(environ, start_response):
	start_response('200 OK', [('Content-Type', 'text/html')])
	return open('index.html', 'rb')


	def main(action):
	if action == 'webserver':
	with make_server('', 8000, wsgiapplication) as httpd:
	print("Serving on port 8000...")

	try:
	httpd.serve_forever()
	except KeyboardInterrupt:
	httpd.shutdown()

	elif action == 'tailserver':
	tail_server = websockets.serve(tail, '', 9000)
	loop.run_until_complete(tail_server)
	loop.run_forever()


	if __name__ == '__main__':
	assert len(sys.argv) == 3, "Required at least two arguments, action and log path."

	_, action, path = sys.argv

	options['path'] = path

	main(action)