GetDirectories

function Get-Directories
{
	[CmdletBinding()]
	param
	(
		[Parameter(Mandatory = $true,
				   ValueFromPipeline = $true,
				   Position = 0)]
		[System.IO.FileInfo]$Path,
		[Parameter(Position = 1)]
		[String]$SearchPattern = '*.*'
	)
	
	Begin
	{
		# an arraylist to hold the results
		$result = New-Object -TypeName System.Collections.ArrayList
		
		# a stack object to push directories that needs to be processed
		$pending = New-Object System.Collections.Generic.Stack[String]
		
	}
	Process
	{
		# push all provided paths to the stack
		foreach ($entry in $Path)
		{
			$pending.Push($entry)
		}
		
		# loop through the stack
		while ($pending.Count -ne 0)
		{
			# current item to process
			$current = $pending.Pop()
			try
			{
				# get all subdirectories from the current one
				# handle in try..catch e.g. to catch Access Denied
				$next = [IO.Directory]::GetDirectories($current, $SearchPattern)
				if ($null -ne $next)
				{
					ForEach ($dir in $next)
					{
						# add directory to the result list
						[void]$result.Add($dir)
					}
				}
			}
			# ignore exceptions
			catch { }
			
			try
			{
				# we need to call GetDirectories for all directories that we found
				$next = [IO.Directory]::GetDirectories($current, $SearchPattern)
				ForEach ($dir in $next)
				{
					# push subdir to stack
					$pending.Push($dir)
				}
			}
			# ignore exceptions
			catch { }
		}
		
	}
	End
	{
		return $result	
	}
}