Start App From Commandline And Return Version Info?

I am developing an application that will run with a GUI when no commandline args are passed, but can also run invisibly if started from the commandline and passed necessary arguments. I have been asked to include a /version argument that will return a version number. For simplicity this version number can be stored in a variable. Without doing something like writing the version number out to a file, what is the best way for me to return this info to the caller? My app will almost always be started from a script, so the script will have to read the version number and make decisons based on the version.