How to get the drive a file is on (was Re: /bin/pwd, cygpath -wa fail under native symlink)

[Ernie Rael <err at raelity dot com>]

I need to find out the drive on which some files reside.

I need to make some links from a tmp dir to the files from a script. So 
I need to determine where they reside so I can figure out which tmp dir 
to use. Hard links, not running as administrator.

I tried cygpath -wa and /bin/pwd. They fail in some cases as described 
below. If this is a problem for cygwin, is there a win7 command I can use?

-ernie

On 12/25/2019 2:05 PM, Ernie Rael wrote:
> (CYGWIN_NT-6.1 spirit 3.1.1(0.340/5/3) 2019-12-18 09:28 x86_64 Cygwin, 
> win7)
>
> The windows root is C:, cygwin root is on F:.
> A native symlink under C: that points into F: gets
> an incorrect result from cygpath -wa.
>
> Notice that when the current directory is the target of the symlink
> then the result is ok. But any deeper in the tree fails. To summarize:
>
>     @ /a/src/jvi-dev/jvi
> $ cygpath -wa .
> C:\f\src\jvi-dev\jvi <<<<<<< correct
>     @ /a/src/jvi-dev/jvi/src
> $ cygpath -wa .
> C:\a\src\jvi-dev\jvi\src <<<<<<< fail
>
> === more detail ===
>
>     @ /a/src/jvi-dev
> $ ls -l jvi
> lrwxrwxrwx 1 erra None 18 Dec 23 15:16 jvi -> /f/src/jvi-dev/jvi
>
>     @ /a/src/jvi-dev
> $ junction jvi
>
> Junction v1.06 - Windows junction creator and reparse point viewer
> Copyright (C) 2000-2010 Mark Russinovich
> Sysinternals - www.sysinternals.com
>
> C:\a\src\jvi-dev\jvi: SYMBOLIC LINK
>    Print Name     : C:\f\src\jvi-dev\jvi
>    Substitute Name: \??\C:\f\src\jvi-dev\jvi
>
>     @ /a/src/jvi-dev
> $ cygpath -wa jvi
> C:\a\src\jvi-dev\jvi
>
>     @ /a/src/jvi-dev
> $ cd jvi
>
>     @ /a/src/jvi-dev/jvi
> $ cygpath -wa .
> C:\f\src\jvi-dev\jvi <<<<<<< correct
>
>     @ /a/src/jvi-dev/jvi
> $ cd src
>
>     @ /a/src/jvi-dev/jvi/src
> $ cygpath -wa .
> C:\a\src\jvi-dev\jvi\src <<<<<<< fail
>
> === some possibly relevent stuff from the mount table
>
> $ mount
> F:/cygwin64 on / type ntfs (binary,auto)
> C:/f on /f type ntfs (binary,user)
> F:/c on /c type ntfs (binary,user)
> F: on /cygdrive/f type ntfs (binary,posix=0,user,noumount,auto)
>
>
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