What's wrong with my recursive delete? - powershell

Question

Get-ChildItem -recurse | ? {$_.Extension -eq ".obj" } | %{del $_}
~~~~~~
CategoryInfo : ObjectNotFound: (C:\Temp\compilerLimits\template.obj:String) [Remove-Item], ItemNotFoundException
FullyQualifiedErrorId : PathNotFound,Microsoft.PowerShell.Commands.RemoveItemCommand
Trying to recursively delete all .obj files;
instead I get this.

Answer 1

Try it like this:
Get-ChildItem -recurse *.obj | Remove-Item
In the case of | %{del $_}, $_ is a System.IO.FileInfo object and when PowerShell uses this for the LiteralPath parameter, it sees that the LiteralPath parameter takes a string. The conversion of FileInfo to a string seems to use the FileInfo.ToString() method which in some cases (like for subdirs) doesn't include the full path - just the filename. That will cause the error your are seeing. When you pipe in the FileInfo object, pipeline argument binding rules are used. The LiteralPath parameter has an alias called PSPath. This property is added to each FileInfo object by PowerShell's type system. You can see this with Get-ChildItem *.obj | Get-Member. And since the LiteralPath parameter has ValueFromPipelineByPropertyName set to true, PowerShell will get the argument value from the object's PSPath property.
You can read more about this in Item 8 of my Effective PowerShell ebook.