[R] File path expansion

[Prof Brian Ripley]

On Mon, 28 May 2007, Martin Maechler wrote:

>>>>>> "Duncan" == Duncan Murdoch <murdoch at stats.uwo.ca>
>>>>>>     on Fri, 25 May 2007 15:38:54 -0400 writes:
>
>    Duncan> On 5/25/2007 1:09 PM, Prof Brian Ripley wrote:
>    >> On Fri, 25 May 2007, Martin Maechler wrote:
>    >>
>    >>>
>    >>>> path.expand("~")
>    >>> [1] "/home/maechler"
>    >>  Yes, but beware that may not do what you want on Windows
>    >> in R <= 2.5.0, since someone changed the definition of
>    >> 'home' but not path.expand.
>
>    Duncan> A more basic problem is that the definition of "~"
>    Duncan> in Windows is very ambiguous.  Is it my Cygwin home
>    Duncan> directory, where "cd ~" would take me while in
>    Duncan> Cygwin?
>
> most probably not (see below).  The normal R Windows users
> needn't know about Cygwin.

And a Unix-alike should have HOME set, and that overrides everything else 
on R for Windows, so probably yes if running from a Unix-alike shell.

>    Duncan> Is it my Windows CSIDL_PERSONAL folder,
>    Duncan> usually %HOMEDRIVE%/%HOMEPATH%/My Documents?  Is it
>    Duncan> the parent of that folder, %HOMEDRIVE%/%HOMEPATH%?
>
>    Duncan> "~" is a shell concept that makes sense in Unix-like
>    Duncan> shells, but not in Windows.
>
> Hmm..
> Let's just say "~" is a short cut for
> "The user's home directory".
> And yes, that's been a Unix concept for ages, but I think
> Windows had adopted that concept, probably with the above
> %HOMEDRIVE%/%HOMEPATH%

We do explain in the rw-FAQ what R thinks the 'home directory' is on 
Windows.  My comment was that had been altered, and path.expand was not 
altered to follow.  Duncan M suggests that was uninportant, but I thought 
it worth fixing.

> The fact that some of windows software may not "work with"
> the user's home directory (but rather a subdirectory of that),
> may be a separate issue, but then,  "I'm the windows-non-expert"
>
> Martin Maechler
>

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595