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Re: tail

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From: Marco.Su...@gmail.com (Marco Sulla)
Newsgroups: comp.lang.python
Subject: Re: tail
Date: Mon, 2 May 2022 21:40:26 +0200
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by: Marco Sulla - Mon, 2 May 2022 19:40 UTC

On Mon, 2 May 2022 at 00:20, Cameron Simpson <cs@cskk.id.au> wrote:
>
> On 01May2022 18:55, Marco Sulla <Marco.Sulla.Python@gmail.com> wrote:
> >Something like this is OK?
> [...]
> >def tail(f):
> > chunk_size = 100
> > size = os.stat(f.fileno()).st_size
>
> I think you want os.fstat().

It's the same from py 3.3

> > chunk_line_pos = -1
> > pos = 0
> >
> > for pos in positions:
> > f.seek(pos)
> > chars = f.read(chunk_size)
> > chunk_line_pos = chars.rfind(b"\n")
> >
> > if chunk_line_pos != -1:
> > break
>
> Normal text file _end_ in a newline. I'd expect this to stop immediately
> at the end of the file.

I think it's correct. The last line in this case is an empty bytes.

> > if chunk_line_pos == -1:
> > nbytes = pos
> > pos = 0
> > f.seek(pos)
> > chars = f.read(nbytes)
> > chunk_line_pos = chars.rfind(b"\n")
>
> I presume this is because unless you're very lucky, 0 will not be a
> position in the range(). I'd be inclined to avoid duplicating this code
> and special case and instead maybe make the range unbounded and do
> something like this:
>
> if pos < 0:
> pos = 0
> ... seek/read/etc ...
> if pos == 0:
> break
>
> around the for-loop body.

Yes, I was not very happy to duplicate the code... I have to think about it.

> Seems sane. I haven't tried to run it.

Thank you ^^

One person's error is another person's data.

devel / comp.lang.python / Re: tail

devel / comp.lang.python / Re: tail