PowerShell Remove-Item not waiting

问题

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?

回答1:

The Remove-Item command has a known issue.

Try this instead:

if (Test-Path $OUT) 
{ 
    # if exists: empty contents and reuse the directory itself
    Get-ChildItem $OUT -Recurse | Remove-Item -Recurse
}
else
{
    # else: create
    New-Item -ItemType Directory -Path $OUT
}

Note:

• The Get-ChildItem command only finds non-hidden files and subdirectories, so emptying out the target directory may not be complete; to include hidden items too, add -Force.

• Similarly, add -Force to -RemoveItem to force removal of files that have the read-only attribute set.

  • Without -Force, emptying may again be incomplete, but you'll get non-terminating errors in this case; if you want to treat them as terminating errors, add -ErrorAction Stop too.

回答2:

Update: Seemingly there are plans to make the Windows filesystem-item removal APIs synchronous, but they aren't synchronous yet as of Windows 10 version 1903 - see this comment on GitHub.

---

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.

marsze's helpful answer offers a workaround: Instead of recreating the directory, just empty it and reuse it, which bypasses the problem.

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.

回答3:

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

回答4:

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

来源：https://stackoverflow.com/questions/53207678/powershell-remove-item-not-waiting