How does one open the HUD from the command line.

Alt is used to open the HUD in 12.04.

I'd like to use alt to execute a second action as well as open the HUD by having alt execute an executable script.

So Alt = script, that does HUD and other stuff.

I know how to do all of this except call the HUD from the command line.

The HUD service is available as a service on DBus, so if you'd just like to poll it for information you can do that with a gdbus command, like this.

gdbus call --session --dest com.canonical.hud --object-path /com/canonical/hud --method com.canonical.hud.StartQuery "my query" 5

If you're trying to get Unity to show the HUD prompt you can do that with the XTest extension using xdotool like this:

xdotool key alt

If you're interested in playing with HUD it's probably best to use the hud-gtk tool which is in the indicator-appmenu-tools package.

You can query the hud from the command line using hud-cli, but it doesn't actually raise the Unity side of hud and it doesn't let you activate the results. It's really only useful for testing hud searches.

I don't think there is a way to do what you are describing at this time.