This is more of a self-documenting post, as it doesn't come up often but when it does, it's not immediately trivial. I'm talking about batch renaming a bunch of files in a folder.

In my particular case, I wanted to make this change:

Desktop 06.17.2017 - 22.34.02.01.mp4 -> Ori of the Blind Forest 06.17.2017 - 22.34.02.01.mp4

So it's a simple prefix change. Normally, I stay stick to using Command Prompt in Cmder. If you haven't used this on Windows, it makes Command Prompt much more usable. It includes some of the command line tools our friends in Linux land enjoy. Anyway, for a task like this PowerShell is a much more apt tool because of its extensive built-in commands.

TL;DR

If you want to replace the prefix (or any other part) of a filename with another type this command:

dir | Rename-Item -NewName {$_.name -replace "old-text","new-text"}

Explanation

Let's breakdown the commands used here:

  1. Get-ChildItem
  2. |
  3. Rename-Item
  4. {...}

First, Get-ChildItem is aliased to dir, but what that command does is output every item in the current directory as an item. The |, or pipe, is used to pass each Item to the Rename-Item command.

Rename-Item has the following anatomy (simplified for this use case):

Rename-Item [-Path] <String> [-NewName] <String>

The [-Path] is coming from dir and [-NewName] is the result of the script block — {...}. The script block is an anonymous function that executes in place, in this case it is using the automatic variable, $_, which is an Item that came from the pipe. The function calls the .name attribute which returns a String, then we can call it's -replace flag which will do what we want.

If we execute this command:

Rename-Item -NewName {$_.name -replace "Desktop","Ori of the Blind Forest"}

Taking this step by step and execute dir:

M:\Media\Videos\ShadowReplay\Ori of the Blind Forest
λ  dir

    Directory: M:\Media\Videos\ShadowReplay\Ori of the Blind Forest

Mode                LastWriteTime         Length Name
----                -------------         ------ ----
-a----        6/17/2017  10:34 PM       12703402 Desktop 06.17.2017 - 22.34.02.01.mp4

So then the command past the pipe will look like this:

Rename-Item Desktop 06.17.2017 - 22.34.02.01.mp4 -NewName {Desktop 06.17.2017 - 22.34.02.01.mp4 -replace "Desktop","Ori of the Blind Forest"}

Then finally reducing to:

Rename-Item Desktop 06.17.2017 - 22.34.02.01.mp4 -NewName Ori of the Blind Forest 06.17.2017 - 22.34.02.01.mp4

I hope this helps someone, I know it'll definitely help me in the future!