$ npm install require-main-filename
require.main.filename is great for figuring out the entry
point for the current application. This can be combined with a module like
pkg-conf to, as if by magic, load
top-level configuration.
Unfortunately, require.main.filename sometimes fails when an application is
executed with an alternative process manager, e.g., iisnode.
require-main-filename is a shim that addresses this problem.
var main = require('require-main-filename')()
// use main as an alternative to require.main.filename.
ISC