Script help: how to invoke grails install-plugin

Hi,
I have several small grails projects all using some common plugins. I am trying to write a groovy script, that lives outside of a grails project which can install a common plugin to all of my grails projects.

basically I need it to copy the plugin zip to the grails project dir, then invoke "grails install-plugin <zip>" from each project dir.

I can figure out the copy part, but am having trouble with the plugin installation part.

Any help appreicated