[lnkForumImage]
TotalShareware - Download Free Software
Confronta i prezzi di migliaia di prodotti.
Asp Forum
 Home | Login | Register | Search 


 

Forums >

comp.lang.ruby

wrong File::SEPARATOR ?

Ronald Fischer

9/14/2007 9:52:00 AM

On my Ruby 1.8.5 under Windows, I have:

C:> ruby -e 'puts File::SEPARATOR'
/

Shouldn't it output '\' instead?

Ronald
--
Ronald Fischer <ronald.fischer@venyon.com>
Phone: +49-89-452133-162
10 Answers

Dan Zwell

9/14/2007 10:12:00 AM

0

Ronald Fischer wrote:
> On my Ruby 1.8.5 under Windows, I have:
>
> C:> ruby -e 'puts File::SEPARATOR'
> /
>
> Shouldn't it output '\' instead?
>
> Ronald

Nope, this variable correct because within ruby and its core libraries,
everything can open files with forward slash separated paths. Try it. It
is probably more reliable than using paths with backslashes (no
potential for confusing the file separator with the escape character).
Now, if you need to pass the path to a non-ruby app, then you will need
to convert them to backslashes.

Dan

Ronald Fischer

9/14/2007 10:48:00 AM

0

> Nope, this variable correct because within ruby and its core
> libraries,
> everything can open files with forward slash separated paths.
> Try it.

I know, and that's what I am doing anyway. I just thought - after
reading about File::SEPARATOR - that this would be a good way
to pass path parameters on to external processes.

So this is not OS dependend, and within *every* Ruby implementation
it is supposed to be a slash ... not that much sense defining
it as a named constant then, isn't it?

Ronald

Dan Zwell

9/14/2007 11:48:00 AM

0

Ronald Fischer wrote:
>> Nope, this variable correct because within ruby and its core
>> libraries,
>> everything can open files with forward slash separated paths.
>> Try it.
>
> I know, and that's what I am doing anyway. I just thought - after
> reading about File::SEPARATOR - that this would be a good way
> to pass path parameters on to external processes.
>
> So this is not OS dependend, and within *every* Ruby implementation
> it is supposed to be a slash ... not that much sense defining
> it as a named constant then, isn't it?
>
> Ronald
>
>

You have a point, as I just can't imagine that the file separator used
by Ruby internally will change any time soon (but who knows?). Thinking
about valid use cases, I tried changing the value of this constant, only
to find that File.joint doesn't use the value:

>> File::SEPARATOR = "\\"
(irb):3: warning: already initialized constant SEPARATOR
=> "\\"
>> File.join("c:", "My Documents")
=> "c:/My Documents"
>> File::SEPARATOR
=> "\\"

I would have expected the result to be "c:\\My Documents"

So the best use case (in my opinion) of this variable does not work.
This behavior is in direct contradiction with the documentation for
File.join, by the way (Ruby 1.8.6).

I wonder whether this has been fixed in 1.9? It really does seem a bug
that File.join does not use File::SEPARATOR (when the docs say it does).
I looked at the c code of this function, and it does use a variable
called "separator", but it seems changing File::SEPARATOR does not
change the c variable.

Dan

James Gray

9/14/2007 12:27:00 PM

0

On Sep 14, 2007, at 5:12 AM, Dan Zwell wrote:

> Ronald Fischer wrote:
>> On my Ruby 1.8.5 under Windows, I have:
>> C:> ruby -e 'puts File::SEPARATOR' /
>> Shouldn't it output '\' instead?
>> Ronald
>
> Nope, this variable correct because within ruby and its core
> libraries, everything can open files with forward slash separated
> paths. Try it.

The truth is that Windows itself understands / as a path separator.
It's just that many interfaces, like the DOS shells, do not.

James Edward Gray II

Bill Kelly

9/14/2007 2:11:00 PM

0


From: "James Edward Gray II" <james@grayproductions.net>
> On Sep 14, 2007, at 5:12 AM, Dan Zwell wrote:
>
>> Ronald Fischer wrote:
>>> On my Ruby 1.8.5 under Windows, I have:
>>> C:> ruby -e 'puts File::SEPARATOR' /
>>> Shouldn't it output '\' instead?

Windows ruby does define ALT_SEPARATOR:

>> File::ALT_SEPARATOR
=> "\\"

(Really a single backslash, self-escaped in the inspect.)


>> Nope, this variable correct because within ruby and its core
>> libraries, everything can open files with forward slash separated
>> paths. Try it.
>
> The truth is that Windows itself understands / as a path separator.
> It's just that many interfaces, like the DOS shells, do not.

Just a potential word of caution going forward... I seem to
recall reading on this list awhile back that the Unicode
file API's in Windows *do not* accept forward slashes for
path separators.

(If that's true, then this may be an issue if Unicode filename
support is ever added to win32 ruby... Although I suppose the
conversion from / to \ could be handled behind the scenes.)


Regards,

Bill

Ronald Fischer

9/17/2007 8:20:00 AM

0

> You have a point, as I just can't imagine that the file
> separator used
> by Ruby internally will change any time soon (but who
> knows?).

I think this can be ruled out, because there probably won't be
too many apps around which just *know* that Ruby accepts /, and
have slashes hardcoded everywhere. I too have never thought about
the existence of File::SEPARATOR as a constant, and came accross
it only when I wanted to construct file names for external applications,
which should be OS independent.

Ronald

Ronald Fischer

9/17/2007 8:22:00 AM

0

> The truth is that Windows itself understands / as a path separator.
> It's just that many interfaces, like the DOS shells, do not.

And that's exactly the problem: When shelling out to external programs,
and / is there usually interpreted as leading in an option (like "-"
does in Posix like systems).

Ronald

Ronald Fischer

9/17/2007 8:24:00 AM

0

> Windows ruby does define ALT_SEPARATOR:
>
> >> File::ALT_SEPARATOR
> => "\\"

Is it guaranteed to also exist on Linux or Mac Ruby, having the
value '/' on those systems?

Ronald
--
Ronald Fischer <ronald.fischer@venyon.com>
Phone: +49-89-452133-162

Eric Hodel

9/17/2007 8:33:00 AM

0

On Sep 17, 2007, at 01:23, Ronald Fischer wrote:
>> Windows ruby does define ALT_SEPARATOR:
>>
>>>> File::ALT_SEPARATOR
>> => "\\"
>
> Is it guaranteed to also exist on Linux or Mac Ruby, having the
> value '/' on those systems?

Those systems don't have an alternate separator so it is set to nil.

--
Poor workers blame their tools. Good workers build better tools. The
best workers get their tools to do the work for them. -- Syndicate Wars

Phlip

9/26/2007 12:23:00 AM

0

Ronald Fischer wrote:

> On my Ruby 1.8.5 under Windows, I have:

C:> ruby -e 'puts File::SEPARATOR'
/

> Shouldn't it output '\' instead?

Not sure if this is answered yet, but Windows accepts /. That prevents
endless hacks in all the legacy code that Windows must support.

Now all we need is a Notepad.exe that, between getting every encoding in the
world correct, will respectfully display a lowly \n correctly...

--
Phlip