Hi Stephen,
it seems you are using an old version of my “Execute a Script in Terminal” plugin. Go here for the latest version, which allows you to use KM variables and is also updated for KM8. [1]
But for your purposes here you don’t need that plugin (unless I’m misunderstanding). It works better with the KM standard action “Execute Shell Script”:
(The sole purpose of my Execute in Terminal plugin is to run a shell script open in the Terminal, as opposed to the “normal”, hidden shell.)
[1] Before you download a macro or a plugin from a thread on the forum, it is always a good idea to scroll down towards the latest post in the thread of that macro/plugin. This is because when the author of the macro/plugin posts an update after a couple of weeks or so, he is no longer allowed to modify the original post. Hence you’ll find the latest versions of macros/plugins often in a separate, later post on the thread.