Comment 1 for bug 1401083

Here is the docsctring for UNIX-NAMESTRING:

    "Given a non-wild PATHNAME, return a Unix-style namestring for it.
If the PATHNAME is NIL or a STRING, return it unchanged.

This only considers the DIRECTORY, NAME and TYPE components of the pathname.
This is a portable solution for representing relative pathnames,
But unless you are running on a Unix system, it is not a general solution
to representing native pathnames.

An error is signaled if the argument is not NULL, a STRING or a PATHNAME,
or if it is a PATHNAME but some of its components are not recognized."

So I'm afraid UIOP:UNIX-NAMESTRING is simply the wrong function to do what you want.

I will close this as INVALID, unless you would like to turn it into a feature request for a new function that WILL do what you want. If so, please add a comment with a specification for the function you would like to see.