[Tutor] script follows a file into zip?

[richard kappler]

Ah, I see, makes perfect sense now that it's right under my nose. Thanks
Peter!

regards, Richard

On Fri, Feb 5, 2016 at 12:04 PM, Peter Otten <__peter__ at web.de> wrote:

> richard kappler wrote:
>
> > I have a script that checks a file and if there are new additions to the
> > file, parses and sends the new additions. This log rolls over and zips at
> > midnight creating a new log of the same name. The problem is, when the
> > file rolls over, the new file seems to follow the old file the way the
> > script is currently written.
> >
> > Current script (edited for brevity):
> > #######################################
> > from time import sleep
> >
> > f1 = open('theFile.log', 'r')
> >
> > f1.seek(0,2)
> > eof = f1.tell()
> >
> > While True:
> >     try:
> >         #check file size to see if grown, set neweof
> >         f1.seek(0,2)
> >         neweof = f1.tell()
> >     except ValueError:
> >         f1 = open(rd1, 'r')
> >         f1.seek(0,2)
> >         neweof = f1.tell()
> >
> >     #if the file is larger...
> >     if neweof > eof:
> >         do a bunch of stuff
> >
> >         # update log.txt file size
> >         eof = neweof
> >         time.sleep(10)
> >
> >     elif neweof < eof:
> >         # this resets eof at night when old log file zipped and new log
> > file started
> >         eof = 0
> >         time.sleep(10)
> >
> >     elif neweof == eof:
> >          # file hasn't changed, do nothing
> >          time.sleep(10)
> > #############################################
> >
> > The script works great all day until the logrotate at midnight. I would
> > expect to get the elif neweof < eof bit then, but my log shows I'm
> getting
> > elif neweof == eof for the rest of the night, which is what leads me to
> > believe that the script, as written, is following the zipped file, not
> > looking at the new file.
> >
> > I have two thoughts on this, not sure which to use, or if something else
> > completely might be appropriate.
> > 1. Instead of
> >
> > f1 = open('theFile.log', 'r')
> >
> > while True:
> > ....
> >
> > Would it make a difference if I used
> >
> > with open('theFile.log', 'r') as f1:
> >     while True:
> > and so on
>
> No. The problem is that you keep the file open. When the file is
> overwritten
> by another application only the entry in the file system is replaced while
> the underlying file (identified by its inode) is kept.
>
> The file you see has now no entry in the file system and therefore could
> only be changed by you; as you only read it no more changes will happen.
>
> To see the file that is  is currently registered under the name
> "theFile.log" you have to reopen:
>
> while True:
>     with open("theFile.log") as f1:
>         ...
>
>
> > 2. Get rid of the elif neweof == eof statement and just make it
> > else:
> >    pass
> >
> > to send it back to the beginning of the loop (doesn't make sense to me,
> > but wanted to throw it out there).
> >
> > regards, Richard
>
>
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