On 2/13/22, Eric Fahlgren <ericfahlg...@gmail.com> wrote:
>
> That may or may not work as Windows has inconsistent treatment of multiple
> separators depending on where they appear in a path. If TEMP is a drive
> spec, say "t:\", then it expands to "t:\\spam.csv", which is an invalid
> windows path. If TEMP is a directory spec, "c:\temp\", then it expands to
> "c:\temp\\spam.csv", which works fine.
>
> C:\> dir c:\\temp\junk
> The filename, directory name, or volume label syntax is incorrect.
"c:\\temp\junk" isn't always invalid in CMD, and definitely not in the
Windows API. The problem occurs because the DIR command in the CMD
shell has legacy support to ignore the drive (e.g. "C:") when the root
of the path is exactly two backslashes -- because DOS in the 1980s
(i.e. they went out of their to add this behavior in CMD to make it
compatible with DOS).
To see this, check the "C$" administrative share on "localhost":
C:\>dir /b C:\\localhost\C$\Temp\spam.txt
File Not Found
C:\>echo spam >C:\\Temp\spam.txt
C:\>dir /b C:\\localhost\C$\Temp\spam.txt
spam.txt
Even though using two backslashes for the root of a drive path is
allowed in the Windows API itself, it's sill problematic. The path
part r"\\path\to\file" can't be used as relative to the current drive
of the process because it's always a UNC absolute path. So it should
be normalized to r"\path\to\file" as soon as possible, e.g. via
GetFullPathNameW():
>>> print(nt._getfullpathname(r'C:\\path\to\file'))
C:\path\to\file
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