tail

[Marco Sulla]

On Mon, 2 May 2022 at 00:20, Cameron Simpson <cs at cskk.id.au> wrote:
>
> On 01May2022 18:55, Marco Sulla <Marco.Sulla.Python at 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 ^^