windows 8.1 - How to recursively remove all empty folders in PowerShell?

Question

I need to recursively remove all empty folders for a specific folder in PowerShell (checking folder and sub-folder at any level).

At the moment I am using this script with no success.

Could you please tell me how to fix it?

$tdc='C:acd'
$a = Get-ChildItem $tdc -recurse | Where-Object {$_.PSIsContainer -eq $True}
$a | Where-Object {$_.GetFiles().Count -eq 0} | Select-Object FullName

I am using PowerShell on Windows 8.1 version.

Answer 1

You need to keep a few key things in mind when looking at a problem like this:

1. Get-ChildItem -Recurse performs head recursion, meaning it returns folders as soon as it finds them when walking through a tree. Since you want to remove empty folders, and also remove their parent if they are empty after you remove the empty folders, you need to use tail recursion instead, which processes the folders from the deepest child up to the root. By using tail recursion, there will be no need for repeated calls to the code that removes the empty folders -- one call will do it all for you.
2. Get-ChildItem does not return hidden files or folders by default. As a result you need to take extra steps to ensure that you don't remove folders that appear empty but that contain hidden files or folders. Get-Item and Get-ChildItem both have a -Force parameter which can be used to retrieve hidden files or folders as well as visible files or folders.

With those points in mind, here is a solution that uses tail recursion and that properly tracks hidden files or folders, making sure to remove hidden folders if they are empty and also making sure to keep folders that may contain one or more hidden files.

First this is the script block (anonymous function) that does the job:

# A script block (anonymous function) that will remove empty folders
# under a root folder, using tail-recursion to ensure that it only
# walks the folder tree once. -Force is used to be able to process
# hidden files/folders as well.
$tailRecursion = {
    param(
        $Path
    )
    foreach ($childDirectory in Get-ChildItem -Force -LiteralPath $Path -Directory) {
        & $tailRecursion -Path $childDirectory.FullName
    }
    $currentChildren = Get-ChildItem -Force -LiteralPath $Path
    $isEmpty = $currentChildren -eq $null
    if ($isEmpty) {
        Write-Verbose "Removing empty folder at path '${Path}'." -Verbose
        Remove-Item -Force -LiteralPath $Path
    }
}

If you want to test it here's code that will create interesting test data (make sure you don't already have a folder c:a because it will be deleted):

# This creates some test data under C:a (make sure this is not
# a directory you care about, because this will remove it if it
# exists). This test data contains a directory that is hidden
# that should be removed as well as a file that is hidden in a
# directory that should not be removed.
Remove-Item -Force -Path C:a -Recurse
New-Item -Force -Path C:acd -ItemType Directory > $null
$hiddenFolder = Get-Item -Force -LiteralPath C:ac
$hiddenFolder.Attributes = $hiddenFolder.Attributes -bor [System.IO.FileAttributes]::Hidden
New-Item -Force -Path C:ae -ItemType Directory > $null
New-Item -Force -Path C:af -ItemType Directory > $null
New-Item -Force -Path C:afg -ItemType Directory > $null
New-Item -Force -Path C:afh -ItemType Directory > $null
Out-File -Force -FilePath C:afest.txt -InputObject 'Dummy file'
Out-File -Force -FilePath C:afhhidden.txt -InputObject 'Hidden file'
$hiddenFile = Get-Item -Force -LiteralPath C:afhhidden.txt
$hiddenFile.Attributes = $hiddenFile.Attributes -bor [System.IO.FileAttributes]::Hidden

Here's how you use it. Note that this will remove the top folder (the C:a folder in this example, which gets created if you generated the test data using the script above) if that folder winds up being empty after deleting all empty folders under it.

& $tailRecursion -Path 'C:a'