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import socket, os, time

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import _utmp

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class WtmpEntry (object) :

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    _ATTRS = (

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        "type", "pid", "line", "id", "user", "host", "exit", "session", "tv", "addr_v6"

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    )

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    @staticmethod

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    def fromFile (file) :

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        bytes = file.read(_utmp.size())

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        if not bytes :

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            return

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        result = _utmp.parse(bytes)

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        wtmp = WtmpEntry()

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        for name, field in zip(wtmp._ATTRS, result) :

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            if isinstance(field, str) and name not in ("addr_v6", ) :

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                field = field.rstrip("\0")

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            setattr(wtmp, name, field)

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        wtmp.addr_v6 = socket.inet_ntop(socket.AF_INET6, wtmp.addr_v6)

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        return wtmp

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    def __str__ (self) :

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        return " ".join("%s=%s" % (key, getattr(self, key)) for key in self._ATTRS)

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class WtmpFile (object) :

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    def __init__ (self, path="/var/log/wtmp") :

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        self.path = path

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        self.file = open(path)

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        self.file.seek(0, os.SEEK_END)

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    def tryRead (self) :

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        return WtmpEntry.fromFile(self.file)

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def read_entries (file) :

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    while True :

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        wtmp = read_entry(file)

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        if wtmp :

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            yield wtmp

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        else :

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            return

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def follow_main () :

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    wtmp = WtmpFile()

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    while True :

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        item = wtmp.tryRead()

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        if item :

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            print item

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        else :

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            time.sleep(2)

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def test_main () :

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    fh = open("/var/log/wtmp", "r")

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    for item in read_entries(fh) :

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        print item

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if __name__ == '__main__' :

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    follow_main()

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