How do I turn the content of a var in an absolute path?

Suppose I have this:

set X = ..

How do I turn that later into an absolute path? Can you please write how it would be in a script?

I 开发者_如何学编程tried with %~dpX , but that gave this error message: The following usage of the path operator in batch-parameter substitution is invalid: %~dpX

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After a lot of searching, I figured out a way of doing this:

for %%y in (%X%) do set X=%%~dpy