Get-FileEncoding.ps1

function Get-FileEncoding {
  ## Get-FileEncoding   http://poshcode.org/2153
  <#

      .SYNOPSIS

      Gets the encoding of a file

      .EXAMPLE

      Get-FileEncoding.ps1 .\UnicodeScript.ps1

      BodyName          : unicodeFFFE
      EncodingName      : Unicode (Big-Endian)
      HeaderName        : unicodeFFFE
      WebName           : unicodeFFFE
      WindowsCodePage   : 1200
      IsBrowserDisplay  : False
      IsBrowserSave     : False
      IsMailNewsDisplay : False
      IsMailNewsSave    : False
      IsSingleByte      : False
      EncoderFallback   : System.Text.EncoderReplacementFallback
      DecoderFallback   : System.Text.DecoderReplacementFallback
      IsReadOnly        : True
      CodePage          : 1201

  #>

  param(
    ## The path of the file to get the encoding of.
    $Path
  )

  Set-StrictMode -Version Latest

  ## The hashtable used to store our mapping of encoding bytes to their
  ## name. For example, "255-254 = Unicode"
  $encodings = @{}

  ## Find all of the encodings understood by the .NET Framework. For each,
  ## determine the bytes at the start of the file (the preamble) that the .NET
  ## Framework uses to identify that encoding.
  $encodingMembers = [System.Text.Encoding] |
  Get-Member -Static -MemberType Property

  $encodingMembers | Foreach-Object {
    $encodingBytes = [System.Text.Encoding]::($_.Name).GetPreamble() -join '-'
    $encodings[$encodingBytes] = $_.Name
  }

  ## Find out the lengths of all of the preambles.
  $encodingLengths = $encodings.Keys | Where-Object { $_ } |
  Foreach-Object { ($_ -split '-').Count }

  ## Assume the encoding is UTF7 by default
  $result = 'UTF7'

  ## Go through each of the possible preamble lengths, read that many
  ## bytes from the file, and then see if it matches one of the encodings
  ## we know about.
  foreach($encodingLength in $encodingLengths | Sort-Object -Descending)
  {
    $bytes = (Get-Content -encoding byte -readcount $encodingLength $path)[0]
    $encoding = $encodings[$bytes -join '-']

    ## If we found an encoding that had the same preamble bytes,
    ## save that output and break.
    if($encoding)
    {
      $result = $encoding
      break
    }
  }

  ## Finally, output the encoding.
  [System.Text.Encoding]::$result
}