Azure - Find Tenant Id for Subscription.ps1

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# PURPOSE: Helper function returns Azure AD Tenant ID for an Azure subscription without 
#          requiring authentication and authorization on subscription

function Get-AzureSubscriptionTenantId ( $subscriptionId )

{

    $uri = "https://management.azure.com/subscriptions/${subscriptionId}?api-version=2015-01-01"

    try 
    {
        $response = Invoke-RestMethod -Method Get -Uri $uri 
    }
    catch 
    {
        $header = $_.Exception.Response.Headers["WWW-Authenticate"]
    }

    $header.Split("/`"")[4]

}

$subId = Read-Host -Prompt "Enter Azure subscription Id"

Get-AzureSubscriptionTenantId -subscriptionId $subId