Rename files to lowercase in Powershell

I am trying to rename a bunch of files recursively using Powershell 2.0. The directory structure looks like this:

Leaflets
+ HTML
  - File1
  - File2
  ...
+ HTMLICONS
  + IMAGES
    - Image1
    - Image2
  - File1
  - File2
  ...
+ RTF
  - File1
  - File2
  ...
+ SGML
  - File1
  - File2
  ...

I am using the following command:

get-childitem Leaflets -recurse | rename -newname { $_.name.ToLower() }

and it seems to rename the files, but complains about the subdirectories:

Rename-Item : Source and destination path must be different.

I reload the data monthly using robocopy, but the directories do not change, so I can rename them by hand. Is there any way to get get-children to skip the subdirectories (like find Leaflets -type f ...)?

Thanks.

UPDATE: It appears that the problem is with files that are already all lower case. I tried changing the command to:

get-childitem Leaflets -recurse | if ($_.name -ne $_name.ToLower()) rename -newname { $_.name.ToLower() }

but now Powershell complains that if is not a cmdlet, function, etc. Can I pipe the output of get-childitem to an if statement?

UPDATE 2: This works:

$files=get-childitem Leaflets -recurse
foreach ($file in $files)
{
    if ($file.name -ne $file.name.ToLower())
    {
        rename -newname { $_.name.ToLower() }
    }
}

Even though you have already posted your own answer, here is a variation:

dir Leaflets -r | % { if ($_.Name -cne $_.Name.ToLower()) { ren $_.FullName $_.Name.ToLower() } }

Some points:

• dir is an alias for Get-ChildItem (and -r is short for -Recurse).
• % is an alias for ForEach-Object.
• -cne is a case-sensitive comparison. -ne ignores case differences.
• $_ is how you reference the current item in the ForEach-Object loop.
• ren is an alias for Rename-Item.
• FullName is probably preferred as it ensures you will be touching the right file.

If you wanted to excludes directories from being renamed, you could include something like:

if ((! $_.IsPsContainer) -and $_.Name -cne $_.Name.ToLower()) { ... }

Hopefully this is helpful in continuing to learn and explore PowerShell.