Get the encoding for a file

Get-FileEncoding.ps1

[CmdletBinding()]
param(
    [Parameter(Mandatory=$True, ValueFromPipeline=$True)]
    [string]$Path
)

$ErrorActionPreference = "Stop"
Set-StrictMode -Version 5.0

$Path = (Resolve-Path $Path).ProviderPath
$reader = [IO.StreamReader]::new($Path)
try {
    # Reading a single character from the file will cause the StreamReader to
    # do encoding detection
    $reader.Read() | Out-Null
    $reader.CurrentEncoding
} finally {
    $reader.Close()
    $reader.Dispose()
}