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Re: One less File::Copy bug

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From:
Aristotle Pagaltzis
Date:
April 28, 2008 05:05
Subject:
Re: One less File::Copy bug
Message ID:
20080428120517.GJ19658@klangraum.plasmasturm.org
* Johan Vromans <jvromans@squirrel.nl> [2008-04-28 12:25]:
> I would propose to a) cleary define the desired semantics of
> copy and b) implement this. There is no need for a BUFFERSIZE
> argument.

It lets the user trade speed for memory or vice versa. It’s not
terribly useful, no, but it doesn’t exactly seem harmful either
(modulo accepting 0 as a buffer size and successfully doing
nothing in that case).

> There is no need for syscopy, copy should do the right job.

If File::Copy hadn’t been around for such a long time, agreed.
However, the old API is what it is.

> There's no need for a cp alias.

I don’t see any reason to throw it out and to old Unix hands it’s
nice to have around. What about it irks you?

> Increase the version number to 3.00. Automatically provide the
> new semantics if the user explicitly requires the new version:
>
>  use File::Copy 3.0;

That is not functionally different from my proposal of allowing
`syscopy` to be imported as `copy`, other than the fact that the
import argument is a meaningless number as opposed to an at least
somewhat descriptive name.

If you really want a new and simpler API, I submit that a new
module name is a better way of handling that. But the old
File::Copy API should still be fixed, as far as it can be.

> As a side note: Wouldn't we all have a good laugh when, say,
> Microsoft, wrote in the docs:
>
>  [...] also provides the syscopy routine, which copies [...]
>  preserving OS-specific attributes and file structure. For Unix
>  systems, this is equivalent to the simple copy routine, which
>  doesn't preserve OS-specific attributes.
>
> This is just stupid.

Of course. That’s why I say that on Unix, `syscopy` should DTRT
as far as it can.

It can’t do a complete job – eg. I doubt it’ll ever be able to
copy XFS attributes of HFS+ resource forks. For apps to be able
to copy files accurately without knowing the implementation
details of every single possible filesystem, the filesystem has
to provide a copy call. But Unix does not define such an
interface, which is of course why `syscopy` has always been a
synonym for `copy` on Unix.

But even so,the system interface situation is not going to
improve, and at the same time, to a certain known extent the Unix
model is universal across filesystems in Unix, so File::Copy is
not merely punting but actively refusing to be helpful.

Regards,
-- 
Aristotle Pagaltzis // <http://plasmasturm.org/>

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