Renaming multiple files with the same extension using PowerShell

Question

I would like to rename just the csv files in my H:/DMU folder. I tried the following code:

 Dir -filter *.csv | %{Rename-Item $_ -NewName ("fn*.csv" -f $nr++)}

I encountered the following error for every file I tried to convert. PowerShell Error Code

I know how to rename all the files in this folder to include the prefix "fn"

Get-ChildItem -Exclude "fn*" |rename-item -NewName {"fn" + $_.Name

, but I just don't know how to rename those of a particular extension.

Answer 1

Looks like you've copied some code that you don't really understand. Where is $nr & why is it being incremented? YOu don't mention wanting to number the files, just add a prefix.

To rename by adding a simple prefix:

gci -filter *.csv | Rename-Item -NewName { 'fn' +$_.Name }

If you want to number:

[ref]$i = 1
gci -filter *.csv | Rename-Item -NewName { 'fn' + $i.Value++ + $_.Name }

If you want 3-place numbering with preceding zeros:

[ref]$i = 1
gci -filter *.csv | Rename-Item -NewName { 'fn{0:d3}{1}' -f $i.Value++, $_.Name }