PowerShell - Editing permissions on a file or folder

JohanS — Wed, 01 Oct 2008 15:52:49 GMT

I got the following question from a reader the other day:

I've been trying to figure out how to change permissions on a folder in PowerShell. I've looked at the Get-Acl and Set-Acl, but I can only use them to copy the settings from a pre-existing object. How do I manually configure permissions?

This is actually a quite common question, so I thought I'd write a quick post on the subject.

Get-Acl and Set-Acl

To quote the PowerShell documentation "Get-Acl gets the security descriptor for a resource, such as a file or registry key." while "Set-Acl changes the security descriptor of a specified resource, such as a file or a registry key." In other words; if you want Folder_A to have the exact same permissions as Folder_B, then you simply copy the Access Control List (ACL) of Folder_B and "paste" it onto Folder_A.

$Acl = Get-Acl "C:\Folder_B"
Set-Acl "C:\Folder_A" $Acl

So far, so good.

Changing the ACL

Okay, so you want to change the ACL. Here's some sample code for how to do that:

New-Item -type directory -path C:\MyFolder
$Acl = Get-Acl "C:\MyFolder"
$Ar = New-Object  system.security.accesscontrol.filesystemaccessrule("username","FullControl","Allow")
$Acl.SetAccessRule($Ar)
Set-Acl "C:\MyFolder" $Acl

So, first we create a new folder. We then copy the ACL of that folder. We then create a new AccessRule that gives "username" full control. We then add this AccessRule to the ACL, and finally we reapply the new, altered ACL to the folder.

If we wanted to we could also have used $Acl.RemoveAccessRule($Ar) or possibly $Acl.RemoveAccessRuleAll() as well.

/ Johan

PowerShell - Automatically organizing your mp3-collection

JohanS — Tue, 23 Sep 2008 14:53:23 GMT

Is your mp3-collection perfectly sorted? I know mine wasn't. I thought I'd address that while creating a pretty good demo-script to show some basic filtering, script structures, etc. Since I also wanted the script to extract the metadata from every file in my collection I had to use the Shell.Application Com-object as well. All in all I think it turned out pretty well.

NOTE:

This script is provided completely as is. It is not an official product in any way and I take no responsibility for any harm it may cause.

Please note that certain metadata editors that integrate directly into the Shell may cause some severe confusion in the metadata, so I'd recommend disabling them before trying. Off course I would also recommend making a backup copy of the music library before surrendering it to the mercy of PowerShell.

If you're new to PowerShell and haven't done so already I'd recommend looking at my earlier posts on the subject:
PowerShell - An introduction, Part I
PowerShell - An introduction, Part II

The script

Param([String] $Folder)
$INVALIDCHARS = [System.IO.Path]::GetInvalidPathChars() + "/", "\", "*", "?", ":"
$MUSICATTRIBS = "*.m4a", "*.m4b", "*.mp3", "*.mp4", "*.wma", "*.flc"
$PLAYLISTATTRIBS = "*.m3u", "*.zpl"
$ALLATTRIBS = $MUSICATTRIBS + $PLAYLISTATTRIBS
$PLAYLISTSFOLDER = "Playlists"
$objShell = New-Object -ComObject Shell.Application
$iTotalFiles = 0
$iCurrentFile = 0

function checkFolderName($FolderName)
{
	# Make sure the folder doesn't contain any invalid characters

	if(!$FolderName) { $FolderName = "Unknown" }
	$INVALIDCHARS | % {$FolderName = $FolderName.replace($_, "")}
	return $FolderName
}



function MoveFiles($startDir)
{
	Write-Host "Indexing playlists..."
	
	# Do a recursive DIR in the starting directory, include everything with the attributes of a playlist.
	# Filter the result by excluding everything that is a Container (folder)
	$dirResult = get-childitem -force -path $startDir -recurse -include $PLAYLISTATTRIBS | where{! $_.PSIsContainer}
	if($dirResult)
	{
		Write-Host "Moving playlists..."

		foreach($dirItem in $dirResult)
		{
			move-item $dirItem.FullName ($PLAYLISTSFOLDER + "\" + $dirItem.Name)
		}
	}
	Write-Host "Indexing music..."

	# Do a recursive DIR in the starting directory, include everything with the attributes of a music file.
	# Again we filter the result by excluding everything that is a Container.
	$dirResult = get-childitem -force -path $startDir -recurse -include $MUSICATTRIBS | where{! $_.PSIsContainer}
	
	# Make a note of how many hits we got, so we can show the progress to the client.
	$iTotalFiles = $dirResult.Count
	if($dirResult)
	{
		foreach($dirItem in $dirResult)
		{
			# Up the counter for how many files we've processed so that we can show progress
			$iCurrentFile +=1

			# Get the metadata for the file
			$fileData = getMP3MetaData($dirItem.FullName)
			
			# Find the path where we the song should be stored
			$ArtistPath = $fileData["Album Artist"]
			if (!$ArtistPath) { $ArtistPath = $fileData["Artists"] }
			if (!$ArtistPath) { $ArtistName = "Unknown" }

			# Make shure it's a valid path
			$ArtistPath = checkFolderName($ArtistPath)
			$AlbumPath = checkFolderName($fileData.Album)
			$ArtistPath = join-path $startDir $ArtistPath 
			$AlbumPath = join-path $ArtistPath $AlbumPath

			# Check if the file should be moved
			if($dirItem.DirectoryName -ne $AlbumPath)
			{
				if(!(test-path $ArtistPath)) # If the Artist folder doesn't exist
				{
					MKDIR $ArtistPath | out-null
				}
				if(!(test-path $AlbumPath)) # If the Album folder doesn't exist
				{
					MKDIR $AlbumPath | out-null
				}
				move-item $dirItem.FullName ($AlbumPath + "\" + $dirItem.Name)
			}

			# Show progress
			$percentage = ([int](($iCurrentFile / $iTotalFiles)*100))
			cls
			Write-Host "$percentage% ($iCurrentFile files of $iTotalFiles) complete"
		}
	}
}


function removeEmptyFolders($startDir)
{
	# Get all folders and subfolders
	$dirResult = Get-childitem $startDir -recurse | where{$_.PSIsContainer}
	if($dirResult)
	{
		foreach($dirItem in $dirResult)
		{
			# If the folder is empty (Doesn't contain any music or playlists) it should be deleted
			if(isfolderempty($dirItem.FullName))
			{
				# Check if the path is still valid, we may have deleted the folder already recursively.
				if(Test-Path $dirItem.FullName)
				{
					remove-item -path $dirItem.FullName -force -recurse
				}
			}
		}
	}
}

function removeOtherFiles($startDir)
{
	# Get all non-music files (except *.jpg-files) and remove them 
	$dirResult = Get-childitem $startDir -recurse -exclude ($ALLATTRIBS + "*.jpg") | where{! $_.PSIsContainer}
	if($dirResult)
	{
		foreach($dirItem in $dirResult)
		{
			if(Test-Path $dirItem.FullName)
			{
				# Make sure the file still exists, and hasn't been deleted already
				remove-item -path $dirItem.FullName -force
			}
		}
	}
}

function isFolderEmpty($folderPath)
{
	# Search for any remaining music items in the folder.
	if(Test-Path $folderPath)
	{
		$dirChildren = get-childitem -force -path $folderPath -recurse -include $ALLATTRIBS | where{! $_.PSIsContainer}
		if($dirChildren -ne $null)
		{
			return $false
		}
		else
		{
			return $true
		}
	}
	else
	{
		# No use trying to delete the folder if it doesn't exist
		return $false
	}
}

function getMP3MetaData($path)
{
	# Get the file name, and the folder it exists in
	$file = split-path $path -leaf
	$path = split-path $path
	$objFolder = $objShell.namespace($path)
	$objFile = $objFolder.parsename($file)
	$result = @{}
	0..266 | % {
		if ($objFolder.getDetailsOf($objFile, $_))
		{
			$result[$($objFolder.getDetailsOf($objFolder.items, $_))] = $objFolder.getDetailsOf($objFile, $_)
		}
	}
	return $result
}

# MAIN FUNCTION

# If no argument was passed, see if anything was piped to the function instead.
if (!$Folder)
{
	$input | % { $Folder = $_ }
}

# Check if the path is valid, if not reset it to ""
if ($Folder) { if (!(Test-Path -path $Folder)) { $Folder = "" }}

# Since no valid path was given, prompt the user for a proper path.
while (!$Folder)
{
	"Please enter the full path to the folder where you wish to rearrange your MP3's"
	$Folder = Read-Host
	if ($Folder) { if (!(Test-Path -path $Folder)) { $Folder = "" }}
}

# Make sure we have a folder to store the playlists in.
$PLAYLISTSFOLDER = join-path $Folder $PLAYLISTSFOLDER
if(!(test-path $PLAYLISTSFOLDER)) # If the Playlists folder doesn't exist
{
	MKDIR $PLAYLISTSFOLDER | out-null
}

# Now that everything is ready, begin rearranging the files.
MoveFiles($Folder)
removeEmptyFolders($Folder)
removeOtherFiles($Folder)

Running the script

So, how do you run this script?

It's quite easy. The first step would be to copy it into notepad save it with a .ps1 extension and open up PowerShell

Execution policy

If this is the first time you try to execute a script from PowerShell you will most likely have to change the execution policy for PowerShell. I'd recommend setting it to RemoteSigned. This (obviously) means that all remote scripts must be signed or PowerShell will refuse to execute them. To change the execution policy simply type:

Set-ExecutionPolicy RemoteSigned

That's it.

If you're uncertain what your execution policy setting is you simply type:

Get-ExecutionPolicy

Okay, having changed that we can now execute the script. If you saved the script in a folder that is in your system path you only need to type the filename of the .ps1 file. (The .ps1 is optional) So, if you saved it as RearrangeMP3s.ps1 you'd write RearrangeMP3s and press enter

Breakdown

Okay, so let's take a look at the separate parts of the script.

Initial variables and constants

First we declare the parameters we're going to use. In this case it's just one: $Folder.

After that we have some constants. You may want to change $MUSICATTRIBS or $PLAYLISTATTRIBS to include, or remove, extensions based on your needs. $PLAYLISTSFOLDER is a constant which indicates in which subfolder you wish to store your playlists.

Finally we have some variables. $objShell is used for file system operations, and rather than creating a new object all the time I'd rather have a global one. $iTotalFiles and $iCurrentFile are two integers used to create a progress indicator.

Functions

After the initial variables come the sub functions called by the main function. To see what each individual function does I'd recommend looking at the comments. I've prioritized readability over minimum number of keystrokes, so yes, instead of writing:

foreach($dirItem in $dirResult)
{
	move-item $dirItem.FullName ($PLAYLISTSFOLDER + "\" + $dirItem.Name)
}

I could have written

$dirResult | % { mv $_.FullName ($PLAYLISTSFOLDER + "\" + $_.Name) }

But in this case I think that would have been counterproductive.

The main function

Finally we have the main function. It is written last in the script. Why is that? Well, actually PowerShell is the most sequential language you'll ever come across. It will not bother to check the entire script for function declarations. Instead it will go through the script one line at a time. This means that the following script will not work:

SayHello

function SayHello
{
	Write-Host "Hello World"
}

When you call SayHello in the sample above the function has not yet been declared, so PowerShell will throw an exception in your face saying that SayHello is unrecognized.

Footnote

There is actually a supported way of achieving the very same thing, but where's the fun in that?

Open up Windows Media Player
Go to Options -> Library and tick the checkbox for "Rearrange music in rip folder"
Go to the "Rip Music"-tab
Make sure the path is correct in the "Rip music to this location"-section
Click OK
Select all files in the library
Right-click and choose the "Advanced Tag Editor"-option
Do not change anything. Simply click Apply
Windows Media Player will now rearrange all the files using your Rip settings.

/ Johan

Stress-O-Matic

JohanS — Mon, 27 Nov 2006 13:41:00 GMT

A very simple stress-test

The other day I was asked by a customer if I a small application that could be used to stress a web application. I didn't feel like responding "Sure I do! Visual Studio 2005 Team Edition For Software Testers" and I also didn't feel like saying "Why don't you make one yourself using the webbrowser control?" So instead I wrote a small script. It's all very basic and simple, but I still thought it might be of use to someone. Just copy the code below into a .vbs-file and you're good to go.

Please note, however that the script relies heavily on WScript.Echo to tracks it's progress, so you should use CScript as the host rather than WScript. If you're unfamiliar with CScript & WScript I recommend taking a look at this article: MSDN: Running Scripts from Windows

CONST NUMBEROFLOOPS = 3 '****** How many times do you want the script to loop?
CONST DELAYTIME = 3 '****** How many seconds do you want to wait?
CONST URL = "http://www.microsoft.com"
Dim Http
Set Http = CreateObject("MSXML2.XMLHTTP")

Main

Function SendHTTPRequest()
   Http.Open "GET", URL , False
   Http.setRequestHeader "If-None-Match","qwerty"
   Http.setRequestHeader "Cache-Control","no-cache,max-age=0"
   Http.setRequestHeader "Pragma","no-cache"
   Http.send
   '****** Uncomment this in case you want to see the response for some reason...
   'WScript.Echo(Http.responseText)
End Function

Sub Main()
   Wscript.Echo("Test started at: " & Now())
   WScript.Echo("Will access """ & URL & """ " & NUMBEROFLOOPS & " times in " & DELAYTIME & " second intervals.")
   For I = 1 to NUMBEROFLOOPS
      WScript.Echo( I & ": Accessing """ & URL & """")
      SendHTTPRequest()
      Wscript.Echo("Waiting " & DELAYTIME & " seconds:")
      For J = DELAYTIME To 1 Step -1
         WScript.Sleep 1000
         Wscript.Echo("Waiting " & J-1 & " seconds:")
      Next
      WScript.Echo( I & ": Complete")
   Next
   Wscript.Echo("Test completed at: " & Now())
End Sub

That's all for now.

/ Johan

Speaking of which... : Script

PowerShell - Editing permissions on a file or folder

Get-Acl and Set-Acl

Changing the ACL

PowerShell - Automatically organizing your mp3-collection

The script

Running the script

Execution policy

Breakdown

Initial variables and constants

Functions

The main function

Footnote

Stress-O-Matic

A very simple stress-test