Skipping files with a given prefix when renaming

Question

I have the following script for renaming a bunch of files in a directory, adding the name of the directory to the start of them:

$s = "Y:\Teknisk Arkiv\Likeretter 111-Å1\E2_Kretsskjema\02_Likeretter styring\3AJJ000302-222"

Get-ChildItem -Path $s -Exclude $_.Directory.Name* | rename-item -NewName { $_.Directory.Name + '_' + $_.Name }

Before running the script the files in the folder looks something like this

after like this

As you can see it does more or less what I want, except that -exclude $_.DirectoryName* doesn't prevent files which already have the foldername as a prefix from being renamed. What am I doing wrong here?

Answer 1

• $_ in a pipeline is only defined inside a script block used in a non-initial pipeline segment, where it refers to the input object at hand, so in your Get-ChildItem command it is effectively undefined.

  • Even if $_.Directory.Name did have a value, $_.Directory.Name* wouldn't work as expected, because it would be passed as 2 arguments (you'd have to use "$($_.Directory.Name)*" or ($_.Directory.Name + '*').

  • You instead want to extract the directory name from the $s input path, which you can do with Split-Path -Leaf, and then append '*'.

• In order for -Exclude to be effective, the input path must end in \*, because -Include and -Exclude filters - perhaps surprisingly - operate on the leaf component of the -Path argument, not on the child paths (unless -Recurse is also specified).

To put it all together:

Get-Item -Path $s\* -Exclude ((Split-Path -Leaf $s) + '*') | 
  Rename-Item -NewName { $_.Directory.Name + '_' + $_.Name }

^{I've switched to Get-Item, since \* is now being used to enumerate the children, but Get-ChildItem would work too.}