PowerShell script to rename extension of files in a specified directory.

Rename-Extension.ps1

<#
.SYNOPSIS
PowerShell script to rename extension of files in a specified directory.

.EXAMPLE
PS> Rename-Extension -Path . -ExtensionFrom txt -ExtensionTo md -Recurse

.PARAMETER Path
Folder that contains the file to be renamed

.PARAMETER ExtensionFrom
Extension name of the conversion source.

.PARAMETER ExtensionTo
Extension name of the conversion destination.

.PARAMETER Recurse
If enabled, recursively change the extension.
#>

param (
    [Parameter(Mandatory=$true)]
    [string]
    $Path,
    [Parameter(Mandatory=$true)]
    [string]
    $ExtensionFrom,
    [Parameter(Mandatory=$true)]
    [string]
    $ExtensionTo,
    [Parameter(Mandatory=$false)]
    [switch]
    $Recurse
)

Get-ChildItem $Path -Filter "*.$ExtensionFrom" -Recurse:$Recurse | ForEach-Object {
    $fullname = $_.FullName
    $newname =  $_.Name -replace "$ExtensionFrom$",$ExtensionTo
    Rename-Item -LiteralPath $fullname -NewName $newname
}