Create a temporary directory in PowerShell?

Question

PowerShell 5 introduces the New-TemporaryFile cmdlet, which is handy. How can I do the same thing but instead of a file create a directory? Is there a New-TemporaryDirec

Answer 1

I think it can be done without looping by using a GUID for the directory name:

function New-TemporaryDirectory {
    $parent = [System.IO.Path]::GetTempPath()
    [string] $name = [System.Guid]::NewGuid()
    New-Item -ItemType Directory -Path (Join-Path $parent $name)
}

Original Attempt With GetRandomFileName

Here's my port of this C# solution:

function New-TemporaryDirectory {
    $parent = [System.IO.Path]::GetTempPath()
    $name = [System.IO.Path]::GetRandomFileName()
    New-Item -ItemType Directory -Path (Join-Path $parent $name)
}

Analysis Of Possibility Of Collision

How likely is it that GetRandomFileName will return a name that already exists in the temp folder?

• Filenames are returned in the form XXXXXXXX.XXX where X can be either a lowercase letter or digit.
• That gives us 36^11 combinations, which in bits is around 2^56
• Invoking the birthday paradox, we'd expect a collision once we got to around 2^28 items in the folder, which is about 360 million
• NTFS supports about 2^32 items in a folder, so it is possible to get a collision using GetRandomFileName

NewGuid on the other hand can be one of 2^122 possibilities, making collisions all but impossible.

Answer 2

.NET has had [System.IO.Path]::GetTempFileName() for quite a while; you can use this to generate a file (and the capture the name), then create a folder with the same name after deleting the file.

$tempfile = [System.IO.Path]::GetTempFileName();
remove-item $tempfile;
new-item -type directory -path $tempfile;