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windowspowershellcmd

What to append to a path to make it point to the file system root?

I have some path, let's say C:\Windows\System32\WindowsPowerShell\. I would like to find such a string, that when appended (from the right side), will make this path point to C:\.

Well, that is easy if the path is set; I could just make it C:\Windows\System32\WindowsPowerShell\..\..\..\.

What I am looking for however, is a fixed string that would work every time, no matter how the initial path looks (and especially how long it is). Does Windows offer some tricks to help this? If it is impossible to achieve, then it's a valid answer.

Bonus points: can I refer to a different hard drive this way?

Solution

  • A fixed string is not an option, but it's easy to dynamically construct one for a given path of arbitrary length.

    Taking advantage of the fact that *, when applied to string on the LHS, replicates that string a given number of times (e.g., 'x' * 3 yields xxx):

    # Sample input path.
$path = 'C:\Windows\System32\WindowsPowerShell'

# Concatenate as many '..\' instances as there are components in the path.
$relativePathToRoot = '..\' * $path.Split('\').Count
$absolutePathToRoot = Join-Path $path $relativePathToRoot

# Sample output
[pscustomobject] @{
  RelativePathToRoot = $relativePathToRoot
  AbsolutePathToRoot = $absolutePathToRoot
}

    Note: On Unix, use '../' * $path.Split('/').Count; for a cross-platform solution, use "..$([IO.Path]::DirectorySeparatorChar)" * $path.Split([IO.Path]::DirectorySeparatorChar).Count; for a solution that can handle either separator on either platform (and uses / in the result), use '../' * ($path -split '[\\/]').Count

    Output:

    RelativePathToRoot AbsolutePathToRoot
------------------ ------------------
..\..\..\..\       C:\Windows\System32\WindowsPowerShell..\..\..\..\