powershell invoke-webrequest to log into website
Don't put a $ for the session variable argument. Try this -
$c = $host.UI.PromptForCredential('Your Credentials', 'Enter Credentials', '', '')$r = Invoke-WebRequest 'http://1.2.3.4/' -SessionVariable my_session$form = $r.Forms[0]$form.fields['username'] = $c.UserName$form.fields['password'] = $c.GetNetworkCredential().Password$r = Invoke-WebRequest -Uri ('http://1.2.3.4' + $form.Action) -WebSession $my_session -Method POST -Body $form.Fields