powershell - Difference between -include and -filter in get-childitem

Question

Can someone please explain the difference between -Include and -Filter options in the Get-ChildItem command .

Below are the two pieces of code that I am trying to execute . They both serve to find out the text files in a particular directory:

PS C:Users352997> get-childitem -path DesktopExtras -filter *.txt


    Directory: C:Users352997DesktopExtras


Mode                LastWriteTime     Length Name
----                -------------     ------ ----
-a---        12/22/2014   4:05 PM        140 Expense_report.txt
-a---         1/14/2015   4:41 PM        211 Extras.txt
-a---         2/10/2015   2:46 PM        259 Learn Dutch.txt

PS C:Users352997> get-childitem -path DesktopExtras -include *.txt

--The above command produces no result ----

Answer 1

1. Filter parameter is implemented by provider. It is efficient because applies when retrieving the objects. Get-PSprovider commandlet shows providers that implement 'filter' parameter. For example, there are only two providers on my system:ActiveDirectory and FileSystem

2. Include parameter is implemented by Powershell. It only works in conjunction with Recurse parameter (as MSDN describes here).

3. It's interesting that:

   get-childitem -path DesktopExtras -include *.txt
   

   returns nothing

   get-childitem -path DesktopExtras* -include *.txt
   

   returns list of *.txt files

Maybe these are just nuances of the implementation.

Also see this excellent blog post: http://tfl09.blogspot.com/2012/02/get-childitem-and-theinclude-and-filter.html