#!/usr/bin/python
# POE has a "FollowTail" wheel that works like tail -F --- if log
# rotation renames the file, creates a new one under the original
# name, and starts appending to it, it switches to watching the new
# file.
# This "followtail" module provides a way to do the same thing in
# Twisted Python.
from __future__ import nested_scopes
import twisted.internet.reactor, os, stat, sys
def file_identity(struct_stat):
return struct_stat[stat.ST_DEV], struct_stat[stat.ST_INO]
def followtail(filename, callback, freq=1, fileobj=None, fstat=None):
if fileobj is None:
fileobj = open(filename)
fileobj.seek(0, 2)
callback(fileobj.read())
if fstat is None: fstat = os.fstat(fileobj.fileno())
try: stat = os.stat(filename)
except: stat = fstat
if file_identity(stat) != file_identity(fstat):
fileobj = open(filename)
fstat = os.fstat(fileobj.fileno())
# don't do this on new files: fileobj.seek(0, 2)
twisted.internet.reactor.callLater(freq, lambda:
followtail(filename, callback, freq,
fileobj, fstat))
if __name__ == '__main__':
followtail(sys.argv[1], sys.stdout.write)
twisted.internet.reactor.run()
