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-TemporaryDirectory cmdlet?

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

I also love one-liners, and I'm begging for a downvote here. All I ask is that you put my own vague negative feelings about this into words.

New-TemporaryFile | %{ rm $_; mkdir $_ }

Depending on the type of purist you are, you can do %{ mkdir $_-d }, leaving placeholder to avoid collisions.

And it's reasonable to stand on Join-Path $env:TEMP $(New-Guid) | %{ mkdir $_ } also.

Answer 3

Here's a variant of user4317867's answer. I create a new directory in the user's Windows "Temp" folder and make the temp folder path available as a variable ($tempFolderPath):

$tempFolderPath = Join-Path $Env:Temp $(New-Guid)
New-Item -Type Directory -Path $tempFolderPath | Out-Null

Here's the same script available as a one-liner:

$tempFolderPath = Join-Path $Env:Temp $(New-Guid); New-Item -Type Directory -Path $tempFolderPath | Out-Null

And here's what the fully qualified temp folder path ($tempFolderPath) looks like:

C:\Users\MassDotNet\AppData\Local\Temp\2ae2dbc4-c709-475b-b762-72108b8ecb9f

Answer 4

If you want the looping solution that is guaranteed to be both race- and collision-free, then here it is:

function New-TemporaryDirectory {
  $parent = [System.IO.Path]::GetTempPath()
  do {
    $name = [System.IO.Path]::GetRandomFileName()
    $item = New-Item -Path $parent -Name $name -ItemType "directory" -ErrorAction SilentlyContinue
  } while (-not $item)
  return $item.FullName
}

According to the analysis in Michael Kropat's answer, the vast majority of the time, this will pass only once through the loop. Rarely will it pass twice. Virtually never will it pass three times.

Answer 5

Here's my attempt:

function New-TemporaryDirectory {
    $path = Join-Path ([System.IO.Path]::GetTempPath()) ([System.IO.Path]::GetRandomFileName())

    #if/while path already exists, generate a new path
    while(Test-Path $path)) {
        $path = Join-Path ([System.IO.Path]::GetTempPath()) ([System.IO.Path]::GetRandomFileName())
    }

    #create directory with generated path
    New-Item -ItemType Directory -Path $path
}

Answer 6

.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;

Answer 7

I love one liners if possible. @alroc .NET also has [System.Guid]::NewGuid()

$temp = [System.Guid]::NewGuid();new-item -type directory -Path d:\$temp

Directory: D:\


Mode                LastWriteTime     Length Name                                                                                                                        
----                -------------     ------ ----                                                                                                                        
d----          1/2/2016  11:47 AM            9f4ef43a-a72a-4d54-9ba4-87a926906948  

Answer 8

if you want, you can be extremely fancy and call Windows API function GetTempPathA() like this:

# DWORD GetTempPathA(
#   DWORD nBufferLength,
#   LPSTR lpBuffer
# );

$getTempPath = @"
using System;
using System.Runtime.InteropServices;
using System.Text;

public class getTempPath {
    [DllImport("KERNEL32.DLL", EntryPoint = "GetTempPathA")]
    public static extern uint GetTempPath(uint nBufferLength, [Out] StringBuilder lpBuffer);
}
"@

Add-Type $getTempPath

$str = [System.Text.StringBuilder]::new()
$MAX_PATH = 260
$catch_res = [getTempPath]::GetTempPath($MAX_PATH, $str)
Write-Host $str.ToString() #echos temp path to STDOUT
# ... continue your code here and create sub folders as you wish ...

1. https://learn.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-gettemppatha

Answer 9

Expanding from Michael Kropat's answer: https://stackoverflow.com/a/34559554/8083582

Function New-TemporaryDirectory {
  $tempDirectoryBase = [System.IO.Path]::GetTempPath();
  $newTempDirPath = [String]::Empty;
  Do {
    [string] $name = [System.Guid]::NewGuid();
    $newTempDirPath = (Join-Path $tempDirectoryBase $name);
  } While (Test-Path $newTempDirPath);

  New-Item -ItemType Directory -Path $newTempDirPath;
  Return $newTempDirPath;
}

This should eliminate any issues with collisions.