[R] how to tell if two file paths refer to the same file

[Duncan Murdoch]

On 11-05-31 3:46 PM, William Dunlap wrote:
> Does R have a standard function that takes two file paths
> (e.g., "./myDirectory/file" and "myDirectory/file")
> and returns TRUE if those paths refer to the same file?

I don't think so.  I think normalizePath is as close as we get portably.

On Windows, toupper(shortPathName()) might do a better job, but I'm sure 
there are exceptions for it too.

And there are the really crazy exceptions, like mapped drives, UNC 
names, etc., where I think it is more or less hopeless to do anything 
without modifying the file.

Duncan Murdoch

>
> The paths make take different routes ("absolute" or
> relative paths or via different symbolic or hard links)
> to the same file or may use different naming conventions
> (Windows or DOS 8.3 on Windows).  If the file paths do not
> refer to actual files the answer is not generally well-defined
> and I'm sure what the best approach would be.
>
> S+ has a match.path() function that is like match() but
> the equality test is that the strings refer to the same
> file.  On Unix it checks that the inode and device numbers
> are the same; on Windows that _fullpath() returns the same
> thing for both paths.  E.g.,
>     >  match.path(c("c:/PROGRA~1",
>                    "c:\\temp",
>                    "C:/Program Files/../Program Files"),
>                  c("C:\\Program Files",
>                    "C:\\Temp"))
>     [1] 1 2 1
>
> I know about R's normalizePath() but it doesn't map all ways
> of refering to a file to the same string so
>     normalizePath(f1) == normalizePath(f1)
> is not a reliable test.  E.g., with R 2.13.0 on Windows it
> doesn't use a standard capitalization:
>     >  cat(normalizePath(c("c:/Program Files",
>                           "C:/program files",
>                           "c:\\PROGRA~1")), sep="\n")
>     c:\Program Files
>     C:\program files
>     c:\Program Files
>
> Bill Dunlap
> Spotfire, TIBCO Software
> wdunlap tibco.com
>
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