param(
    [Parameter(Mandatory=$true)]
    [string]$url
)

function Write-Log($msg)
{
    Write-Host $msg -foregroundcolor green
    ($msg) | Out-File "log-enum-all-users.txt" -Append
}

function Enum-Users($site)
{
	Write-Log ($site.Url)
    $web = $site.RootWeb
	foreach ($g in $web.SiteGroups)
	{
		Write-Log ("  " + $g.Name)
		foreach ($u in $g.Users)
		{
			Write-Log ("    " + $u.LoginName)
		}
	}
}

$webApp = Get-SPWebApplication $url
$webApp.Sites | ForEach-Object { Enum-Users $_ }