Get Domain from URL in PowerShell - powershell

Question

I'm looking to strip out the domain in this scenario using PowerShell. What is the most effective method to get example.com out of the following variable?
$URL = "http://www.example.com/folder/"
(some sort of regex command here to convert/strip $URL into $DOMAIN using PowerShell)
$DOMAIN = "example.com" #<-- taken from $URL
I've searched and I've found results for finding the IP address from a domain but I need to establish what the domain is first using regex (or another method).

Answer 1

Try the URI class:
PS> [System.Uri]"http://www.example.com/folder/"
AbsolutePath : /folder/
AbsoluteUri : http://www.example.com/folder/
LocalPath : /folder/
Authority : www.example.com
HostNameType : Dns
IsDefaultPort : True
IsFile : False
IsLoopback : False
PathAndQuery : /folder/
Segments : {/, folder/}
IsUnc : False
Host : www.example.com
Port : 80
Query :
Fragment :
Scheme : http
OriginalString : http://www.example.com/folder/
DnsSafeHost : www.example.com
IsAbsoluteUri : True
UserEscaped : False
UserInfo :
And remove the www prefix:
PS> ([System.Uri]"http://www.example.com/folder/").Host -replace '^www\.'
example.com

Answer 2

Like this:
PS C:\ps> [uri]$URL = "http://www.example.com/folder/"
PS C:\ps> $domain = $url.Authority -replace '^www\.'
PS C:\ps> $domain
example.com

Answer 3

For properly calculating the sub-domain, the trick is you need to know the second to last period. Then you take a substring of that second to last period (or none if it is only one .) to the final position by subtracting the location of second period (or 0) from total length of domain. This will return the proper domain-only and will work regardless of how many sub-domains are nested under the TLD:
$domain.substring((($domain.substring(0,$domain.lastindexof("."))).lastindexof(".")+1),$domain.length-(($domain.substring(0,$domain.lastindexof("."))).lastindexof(".")+1))
Also note that System URI itself is valid 99% of the time but I'm parsing my IIS logs and finding that with VERY long (often invalid/malicious requests) URIs it does not properly parse and fails those.
I have this in function form as:
Function Get-DomainFromURL {
<#
.SYNOPSIS
Takes string URL and returns domain only
.DESCRIPTION
Takes string URL and returns domain only
.PARAMETER URL
URL to parse for domain
.NOTES
Author: Dane Kantner 9/16/2016
#>
[CmdletBinding()]
param(
[Alias("URI")][parameter(Mandatory=$True,ValueFromPipeline=$True)][string] $URL
)
try { $URL=([System.URI]$URL).host }
catch { write-error "Error parsing URL"}
return $URL.substring((($URL.substring(0,$URL.lastindexof("."))).lastindexof(".")+1),$URL.length-(($URL.substring(0,$URL.lastindexof("."))).lastindexof(".")+1))
}