2

    Iterate over input lines in files. 

     3

     4

    Can be read up to eof, on blocking inputs, or polled with a timeout (see: pvl.syslog.syslog.SyslogSource)

     9

import logging; log = logging.getLogger('pvl.syslog.tail')

    11

class Tail (object) :

    13

        Follow a file-like object, reading lines until EOF.

    14

    15

        Works with python file objects that buffer readlines() when using e.g. `tail -f ... | python -u ...`.

    18

    def __init__ (self, file) :

    19

        self.file = file

    21

    def readline (self) :

    23

            Reads a line from the file, without trailing \n

    24

    25

            Raises EOF on end-of-file.

    28

        line = self.file.readline()

    30

        if not line :

    31

            raise EOFError()

    32

        else :

    33

            return line.rstrip('\n')

    35

    def readlines (self) :

    37

            Reads any available lines from the file.

    40

        while True :

    41

            try :

    42

                line = self.readline()

    44

            except EOFError :

    45

                log.debug("EOF")

    46

                break

    47

    48

            else :

    49

                yield line

    50

    51

    def skip (self) :

    52

        """

    53

            Skip any available lines.

    54

        """

    55

    56

        for line in self.readlines() :

    57

            pass

    58

    59

    __iter__ = readlines

    60

    61

class TailFile (Tail) :

    62

    """

    63

        Follow a file on the filesystem, reading lines until EOF, and re-opening if replaced.

    64

    """

    65

    66

    def __init__ (self, path) :

    67

        self.path = path

    68

        self.reopen()

    69

    70

    def stat (cls) :

    78

    79

    def open (cls) :

    80

        return open(self.path, 'r')

    82

    def reopen (cls) :

    83

        self.file = self.open()

    84

        self._stat = self.stat()

    86

    def changed (self) :

    91

        return self.stat() != self._stat

   107

                if self.changed() :

   108

                    log.debug("EOF: reopen")

   109

                    self.reopen()

   112

                        yield None # special token

   113

   114

                    # keep going

   115

                    continue

   118

                    log.debug("EOF")

   119

                    break # wait

   122

                yield line