Rebuilding registry key from array - arrays

Question

I am trying to take a variable, split it and then rebuild it so I can use Test-Path iteratively. I am not sure it is possible. The code I have so far in its basic form looks something like this, the trouble I have is around rebuilding the registry path.
$Key = "HKCU:\SOFTWARE\MyKey\Test"
$SplitKey = $Key -split "\\"
#Write-Host $SplitKey.Length
$i = 0
do {
if ($i -gt 0) {
$x = $i - 1
$sk = $SplitKey[$x] + "\" + $SplitKey[$i] + "\"
Write-Host $sk
} else {
$sk = $SplitKey[$i] + "\"
Write-Host $sk
}
$i++
} until ($i -ge $SplitKey.Length)
The first part of the key is rebuilt exactly how I want. My plan is to incorporate a Test-Path into the loop and where required do a New-Item if Test-Path fails.
Can anyone help with the loop and rebuilding the $SplitKey array step by step?

Answer 1

This is what causes your problem:
$x = $i - 1
$sk = $SplitKey[$x] + "\" + $SplitKey[$i] + "\"
You create $sk just from the previous and the current array element, which basically works like this:
Original string: HKCU:\SOFTWARE\MyKey\Test
1st iteration: HKCU:\
2nd iteration: HKCU:\SOFTWARE\
3rd iteration: SOFTWARE\MyKey\
4th iteration: MyKey\Test\
What you actually want is to concatenate the current array element to everything that came before, i.e. to the current value of $sk:
$sk += "\" + $SplitKey[$i]
Or you could join the array elements up to the current index:
$sk = $SplitKey[0..$i] -join '\'
With that said, personally I prefer recursive algorithms for path creation. Traverse from the full path up to the longest existing path, then create the missing folders when you descend back down as you return from the recursive calls:
function New-Key([string]$Path) {
$drive = Split-Path $Path -Qualifier
$parent = try { Split-Path $Path -NoQualifier | Split-Path -Parent } catch {}
if (-not (Test-Path -LiteralPath $Path)) {
New-Key (Join-Path $drive $parent)
New-Item -Type Directory -Path $Path
}
}