Delete oldest versions of a directory in PowerShell - powershell

Question

I have a list of directories which are formatted like version numbers and would like to find the N oldest directories and delete them. For example:
/1.2.3.4
/1.2.3.5
/1.2.3.6
I've tried a few things, but I can't quite seem to get where I need to go.
My first try was this:
ls directory | sort Name | select -first 5 | rm -r
However I'm not sure this is going to work in all circumstances, because this will (I presume) do a natural sort. Is that always going to return the correct results?
My next thought was that I could use System.Version to do my sorting. So I ended up with this:
ls directory | %{[System.Version]$_.Name } | sort | select -first 5 | ???
The problem is that I'm not sure how to tie the directory result to the sorting... What's the best way to do this?
gci \\directory produces
Mode LastWriteTime Length Name
---- ------------- ------ ----
d---- 12/19/2011 5:19 PM 1.0.1052.54849
d---- 12/19/2011 5:29 PM 1.0.1053.54850
d---- 12/19/2011 5:36 PM 1.0.1054.54851
d---- 12/20/2011 2:11 PM 1.0.1056.54875
d---- 12/12/2011 10:39 AM 1.0.991.54625
d---- 12/12/2011 12:08 PM 1.0.992.54627
d---- 12/12/2011 12:22 PM 1.0.993.54628
d---- 12/12/2011 1:15 PM 1.0.994.54630
d---- 12/12/2011 2:45 PM 1.0.996.54636
d---- 12/12/2011 3:34 PM 1.0.997.54640
d---- 12/12/2011 3:48 PM 1.0.998.54641
gci \\directory | Sort-Object { $_Name -as [Version] } produces
Mode LastWriteTime Length Name
---- ------------- ------ ----
d---- 12/12/2011 1:15 PM 1.0.994.54630
d---- 12/12/2011 12:22 PM 1.0.993.54628
d---- 12/12/2011 2:45 PM 1.0.996.54636
d---- 12/12/2011 3:48 PM 1.0.998.54641
d---- 12/12/2011 3:34 PM 1.0.997.54640
d---- 12/12/2011 12:08 PM 1.0.992.54627
d---- 12/19/2011 5:29 PM 1.0.1053.54850
d---- 12/19/2011 5:19 PM 1.0.1052.54849
d---- 12/19/2011 5:36 PM 1.0.1054.54851
d---- 12/12/2011 10:39 AM 1.0.991.54625
d---- 12/20/2011 2:11 PM 1.0.1056.54875
Does it matter that this is a network share? I'm confused as to why this isn't working... I did a quick sanity check and doing Array.Sort on versions I've created in a unit test are sorted correctly.

Answer 1

You can actually sort on an expression, which will keep your original objects.
Get-ChildItem $path |
Sort-Object { $_.Name -as [Version] } |
Select-Object -Last 1 |
Remove-Item
Will do the trick.
Hope this helps,

Answer 2

Natural sort is the order that you want. 1,2,3..10,11..instead of 1,10,11,2,3..
1..11 | %{$_.tostring()} | sort
Gives it in "ASCIIbetical" order, which is not the natural order we expect it to be in.
Based on what you were doing with version, I would say you can do like this, though it might be a bit over board:
gci directory | %{new-object psobject -p #{version=[version]($_.name);dir=$_ }} |
sort version | select -expand dir -first 5 | rm -r -whatif
or
gci directory | select #{e={[version] $_.name};l="version"}, #{e={$_};l="dir"} |
sort version | select -expand dir -first 5 | rm -r -whatif