How to normalize a path in PowerShell?

Question

I have two paths:

fred\frog 

and

..\frag 

I can join them together in PowerShell like this:

join-path 'fred\frog' '..\frag' 

That gives me this:

fred\frog\..\frag 

But I don't want that. I want a normalized path without the double dots, like this:

fred\frag 

How can I get that?

Answer 1

You can expand ..\frag to its full path with resolve-path:

PS > resolve-path ..\frag  

Try to normalize the path using the combine() method:

[io.path]::Combine("fred\frog",(resolve-path ..\frag).path) 

Answer 2

You can use a combination of $pwd, Join-Path and [System.IO.Path]::GetFullPath to get a fully qualified expanded path.

Since cd (Set-Location) doesn't change the process current working directory, simply passing a relative file name to a .NET API that doesn't understand PowerShell context, can have unintended side-effects, such as resolving to a path based off the initial working directory (not your current location).

What you do is you first qualify your path:

Join-Path (Join-Path $pwd fred\frog) '..\frag' 

This yields (given my current location):

C:\WINDOWS\system32\fred\frog\..\frag 

With an absolute base, it is now safe to call the .NET API GetFullPath:

[System.IO.Path]::GetFullPath((Join-Path (Join-Path $pwd fred\frog) '..\frag')) 

Which gives you the fully qualified path, with the .. correctly resolved:

C:\WINDOWS\system32\fred\frag 

It's not complicated either, personally, I disdain the solutions that depend on external scripts for this, it's simple problem solved rather aptly by Join-Path and $pwd (GetFullPath is just to make it pretty). If you only want to keep only the relative part, you just add .Substring($pwd.Path.Trim('\').Length + 1) and voila!

fred\frag 

UPDATE

Thanks to @Dangph for pointing out the C:\ edge case.