Get the computer name of the local computer

Get-ComputerName.ps1

<#
.SYNOPSIS
Get the computer name of the local computer

.DESCRIPTION
Return the configured cluster or local computer name of the specified type

.PARAMETER NameFormat
One of: NetBIOS, DnsHostname, DnsDomain, DnsFullyQualified, PhysicalNetBIOS, PhysicalDnsHostname, PhysicalDnsDomain, PhysicalDnsFullyQualified
[COMPUTER_NAME_FORMAT] Definitions: https://msdn.microsoft.com/en-us/library/windows/desktop/ms724224(v=vs.85).aspx

.EXAMPLE
Get-ComputerName -NameFormat PhysicalDnsFullyQualified
#>
function Get-ComputerName {
    [CmdletBinding()]
    [OutputType([string])]

    Param (
        [Parameter()]
        [ValidateSet(
            "NetBIOS",
            "DnsHostname",
            "DnsDomain",
            "DnsFullyQualified",
            "PhysicalNetBIOS",
            "PhysicalDnsHostname",
            "PhysicalDnsDomain",
            "PhysicalDnsFullyQualified"
        )]
        [string]
        $NameFormat = "DnsFullyQualified"
    )

    Begin {
        $Kernel32Definition = '
            public enum COMPUTER_NAME_FORMAT {
                NetBIOS,
                DnsHostname,
                DnsDomain,
                DnsFullyQualified,
                PhysicalNetBIOS,
                PhysicalDnsHostname,
                PhysicalDnsDomain,
                PhysicalDnsFullyQualified
            }

            [DllImport("kernel32.dll", CharSet = CharSet.Auto)]
            public static extern bool GetComputerNameEx(COMPUTER_NAME_FORMAT nameType, System.Text.StringBuilder buffer, ref uint size);
        '

        if (-not ('WinAPI.Kernel32' -as [type])) {
            Add-Type -Namespace "WinAPI" -Name "Kernel32" -MemberDefinition $Kernel32Definition
        }
    }

    Process {
        $ComputerNameBuffer = New-Object -TypeName System.Text.StringBuilder -ArgumentList 256
        $BufferSize = $ComputerNameBuffer.Capacity

        $Result = [WinAPI.Kernel32]::GetComputerNameEx($NameFormat, $ComputerNameBuffer, [ref] $BufferSize)

        if ($Result -eq $False) {
            # An error occured. Display the Win32 error set
            throw (New-Object -TypeName ComponentModel.Win32Exception)
        } else {
            return $ComputerNameBuffer.ToString()
        }
    }

    End {

    }
}