How to handle directories with special characters in their name

Question

I can't figure out how to recode the second clause of this function to handle directories like one named "[]"
function Get-DiskUsage {
# parse and pray (but it does accept directory []
dir |
? { $_.psIsContainer } |
$size = ((@(cmd /c dir /s $_.name)[-2])[25..39] -join '')
if ($size[14] -eq ' ') {
$size = ' ' + ((@(cmd /c dir /s $_.name)[-2])[25..38] -join '')
$name = $_.name
' ' + $size + ' ' + $name
# object oriented, but it does not accept directory []
Get-ChildItem -Directory |
Select-Object @{ Name="Size";
Expression={ ($_ | Get-ChildItem -Recurse |
Measure-Object -Sum Length).Sum + 0 } },
Name

Answer 1

Here is the function with additional functionality to count bytes in the files in the directory itself as well as subdirectories, and accept an optional argument to specify the target directory.  I wish there was a better way
to do this without modifying and later restoring $pwd
function Get-DiskUsage {
# Discovers how much space is allocated in the directories at and below
# the current directory
# Inspired by a version from Windows PowerShell Cookbook by Lee Holmes
# http://www.leeholmes.com/guide
# The change to parse ] and [ correctly in a directory name was created by Rhys W Edwards
# http://social.technet.microsoft.com/Forums/en-US/f4f0a133-8c4d-4089-8047-274dbc03567b
# if there is an argument, then validate it as an actual directory and set $pwd to it
if ($args.length -gt 0) {
if ((Test-Path -Path $args[0] -PathType Container) -eq $False) {
return
$pwdsave = $pwd
cd $args[0]
# count of bytes in the files in the directory itself
(Get-ChildItem | Measure-Object -property length -sum) |
Select-Object @{Name='Size';Expression={$_.Sum}},@{Name='Name';Expression={$pwd}}
# count of bytes in the files in the subdirectories
Get-ChildItem -Directory |
Select-Object @{
Name='Size';
Expression={
( $_ -replace '\[','`[' -replace '\]','`]' |
Get-ChildItem -Recurse |
Measure-Object -Sum Length).Sum + 0 }
},Name
# restore $pwd is needed
if ($args.length -gt 0) {
cd $pwdsave