Run windows update from powershell

Install-WindowsUpdate.ps1

Function Install-WindowsUpdate {
    [CmdletBinding()]
    Param ()
    Process {
        $updateSession = New-Object -ComObject "Microsoft.Update.Session"

        Write-Host "Searching updates..."

        $searcher = $updateSession.CreateupdateSearcher()
        $searchResult = $searcher.Search("IsInstalled=0 and AutoSelectOnWebSites=1")

        if ($searchResult.Updates.Count -eq 0) {
            Write-Host "There are no updates"
            return
        } else {
            Write-Host "Found following updates"
            $searchResult.Updates | Format-Table -AutoSize IsDownloaded, MaxDownloadSize, Title
        }

        Write-Host "Downloading updates..."

        $downloader = $updateSession.CreateUpdateDownloader()
        $downloader.Updates = $searchResult.Updates
        $downloadResult = $downloader.Download()

        if ($downloadResult.ResultCode -ne 2) {
            throw $downloadResult
        }

        Write-Host "Installing updates..."

        $updatesToInstall = New-Object -ComObject "Microsoft.Update.UpdateColl"
        $searchResult.Updates | ? { $_.IsDownloaded } | %{ $updatesToInstall.Add($_) } | Out-Null

        $installer = $updateSession.CreateUpdateInstaller()
        $installer.Updates = $updatesToInstall
        $installResult = $installer.Install()

        if ($installResult.ResultCode -ne 2) {
            throw $installResult
        }

        if ($installResult.RebootRequired) {
            if ($PSCmdlet.ShouldProcess('Restart Computer')) {
                Restart-Computer
            }
        }
    }
}