PowerShell Remove-Item not waiting

Question

If have this piece of code

if(Test-Path -Path $OUT) 
{ 
    Remove-Item $OUT -Recurse 
}
New-Item -ItemType directory -Path $OUT

Sometimes it works, but sometimes the New-Item line produces a PermissionDenied ItemExistsUnauthorizedAccessError error. Which, I assume, means that the previous Remove-Item was not completely performed yet and the folder cannot be created because it still exists.

If I insert a sleep there

if(Test-Path -Path $OUT) 
{ 
    Remove-Item $OUT -Recurse 
    Start-Sleep -s 1
}
New-Item -ItemType directory -Path $OUT

then it works always. How can I force Remove-Item to ensure that the folder is really removed? Or maybe I miss something else?

Answer 1

Update: Starting with (at least ^[1]) Windows 10 version 20H2 (I don't know that Windows Server version and build that corresponds to; run winver.exe to check your version and build), the DeleteFile Windows API function now exhibits synchronous behavior, which implicitly solves the problems with PowerShell's Remove-Item and .NET's System.IO.File.Delete / System.IO.Directory.Delete (but, curiously, not with cmd.exe's rd /s).

---

Remove-Item -Recurse is unexpectedly asynchronous, ultimately because the Windows API methods for file and directory removal are inherently asynchronous and Remove-Item doesn't account for that.

This intermittently, unpredictably manifests in one of two ways:

• Your case: recreating a removed directory immediately after removal can fail, because the removal may not have completed yet by the time re-creation is attempted.

• More typically: Removing a nonempty directory itself can fail, if removal of a subdirectory or file hasn't completed yet by the time an attempt is made to remove the parent directory - this is demonstrated in the ServerFault answer marsze links to.

A potential workaround is to reuse an existing directory by emptying it - instead of deleting and recreating it.

However, emptying the directory with Get-ChildItem $OUT -Recurse | Remove-Item -Recurse is also susceptible to intermittent failures, though likely less often.

The problem not only affects PowerShell's Remove-Item, but also cmd.exe's rd /s as well as .NET's [System.IO.Directory]::Delete():

As of Windows PowerShell v5.1 / PowerShell Core 6.2.0-preview.1 / cmd.exe 10.0.17134.407 / .NET Framework 4.7.03056, .NET Core 2.1, neither Remove-Item, nor rd /s, nor [System.IO.Directory]::Delete() work reliably, because they fail to account for the asynchronous behavior of the Windows API file/directory-removal functions:

• PowerShell Core bug report
• cmd.exe bug report
• .NET Core bug report

For a custom PowerShell function that provides a reliably synchronous workaround, see this answer.

---

^{[1] I've personally verified that the issue is resolved in version 20H2, by running the tests in GitHub issue #27958 for hours without failure; this answer suggests that the problem was resolved as early as version 1909, starting with build 18363.657, but Dinh Tran finds that the issue is not resolved as of build 18363.1316 when removing large directory trees such as node_modules. I couldn't find any official information on the subject.}

Answer 2

For completeness' sake: You can also use the safe and fast .NET methods:

if ([System.IO.Directory]::Exists($OUT)) {
    [System.IO.Directory]::Delete($OUT, $true)
}
[System.IO.Directory]::CreateDirectory($OUT)

Note:

Depending on where you get the value of $OUT you might want to convert it to a full path first to make sure the .NET methods remove the correct directory (see @mklement0`s comment):

$fullPath = Convert-Path $OUT

Answer 3

If you type Get-Help Remove-Item -Detailed you'll see:

Example 4: Delete files in subfolders recursively
PS C:\>Get-ChildItem * -Include *.csv -Recurse | Remove-Item

This command deletes all of the CSV files in the current folder and all subfolder recursively.

Because the Recurse parameter in Remove-Item has a known issue, the command in this example uses Get-ChildItem to get the desired files, and then uses the pipeline operator to pass them to Remove-Item .

Do what specification recommends:

if(Test-Path -Path $OUT) 
{ 
    Get-ChildItem $OUT -Recurse | Remove-Item
}
New-Item -ItemType directory -Path $OUT