Get-FileEncoding.psm1

function Get-FileEncoding {
    <#
    .SYNOPSIS
        To get the file encoding of a file
    .DESCRIPTION
        To get the file encoding of a file
    .PARAMETER Path
        The file that you want to check its encoding.
    .EXAMPLE
        Get-FileEncoding -Path .\UTF16-BigEndian.txt
    
        Unicode UTF-16 Big-Endian
    .EXAMPLE
        Get-FileEncoding -Path .\UTF16-LittleEndian.txt
    
        Unicode UTF-16 Little-Endian
        
        original source: https://gist.github.com/jpoehls/2406504
    #>

    [CmdletBinding()]
    Param (
        [Parameter(Mandatory = $true, Position = 0, ValueFromPipeline = $true, ValueFromPipelineByPropertyName = $true, HelpMessage = 'Please enter the path to a file')]
        [string[]]$Path
    )

    process {
        foreach ($PathItem In $Path) {
            if ((Test-Path -Path $PathItem -PathType Leaf) -eq $false) {
                Write-Error -Message "The file [$Path] does not exist."
                return
            }
            
            [byte[]]$byte = Get-Content -Encoding byte -ReadCount 4 -TotalCount 4 -Path $PathItem

            switch ($true) {
                ( $byte[0] -eq 0xef -and $byte[1] -eq 0xbb -and $byte[2] -eq 0xbf ) {
                    # EF BB BF (UTF8)
                    Write-Output -inputobject 'UTF8'
                    break
                }
                ($byte[0] -eq 0xfe -and $byte[1] -eq 0xff) {
                    # FE FF (UTF-16 Big-Endian)
                    Write-Output -inputobject 'Unicode UTF-16 Big-Endian'
                    break
                }
                ($byte[0] -eq 0xff -and $byte[1] -eq 0xfe) {
                    # FF FE (UTF-16 Little-Endian)
                    Write-Output -inputobject 'Unicode UTF-16 Little-Endian'
                    break
                }
                ($byte[0] -eq 0 -and $byte[1] -eq 0 -and $byte[2] -eq 0xfe -and $byte[3] -eq 0xff) {
                    # 00 00 FE FF (UTF32 Big-Endian)
                    Write-Output -inputobject 'UTF32 Big-Endian'
                    break
                }
                ($byte[0] -eq 0xfe -and $byte[1] -eq 0xff -and $byte[2] -eq 0 -and $byte[3] -eq 0) {
                    # FE FF 00 00 (UTF32 Little-Endian)
                    Write-Output -inputobject 'UTF32 Little-Endian'
                    break
                }
                ($byte[0] -eq 0x2b -and $byte[1] -eq 0x2f -and $byte[2] -eq 0x76 -and ($byte[3] -eq 0x38 -or $byte[3] -eq 0x39 -or $byte[3] -eq 0x2b -or $byte[3] -eq 0x2f) ) {
                    # 2B 2F 76 (38 | 38 | 2B | 2F)
                    Write-Output -inputobject 'UTF7'
                    break
                }
                ( $byte[0] -eq 0xf7 -and $byte[1] -eq 0x64 -and $byte[2] -eq 0x4c ) {
                    # F7 64 4C (UTF-1)
                    Write-Output -inputobject 'UTF-1'
                    break
                }
                ($byte[0] -eq 0xdd -and $byte[1] -eq 0x73 -and $byte[2] -eq 0x66 -and $byte[3] -eq 0x73) {
                    # DD 73 66 73 (UTF-EBCDIC)
                    Write-Output -inputobject 'UTF-EBCDIC'
                    break
                }
                ( $byte[0] -eq 0x0e -and $byte[1] -eq 0xfe -and $byte[2] -eq 0xff ) {
                    # 0E FE FF (SCSU)
                    Write-Output -inputobject 'SCSU'
                    break
                }
                ( $byte[0] -eq 0xfb -and $byte[1] -eq 0xee -and $byte[2] -eq 0x28 ) {
                    # FB EE 28 (BOCU-1)
                    Write-Output -inputobject 'BOCU-1'
                    break
                }
                ($byte[0] -eq 0x84 -and $byte[1] -eq 0x31 -and $byte[2] -eq 0x95 -and $byte[3] -eq 0x33) {
                    # 84 31 95 33 (GB-18030)
                    Write-Output -inputobject 'GB-18030'
                    break
                }
                default {
                    Write-Output -inputobject 'ASCII'
                }
            }
        }
    }
}