Fiji has jython interpreter that allows you to do processing and analysis interactively via console. In case of using it from command line, following command launches the interactive interpreter as it is described in the Fiji website.

./ImageJ --jython

When you are developing a Fiji plugin using Eclipse, you might want to use this interactive functionality from within Eclipse. This could be done by configuring “External tools” as below. If you want to use other scripting language, you could replace the argument to –js, –jruby and so on.