How do I write this to go back up the parent 2 levels to find a file?
fs.readFile(__dirname + 'foo.bar');
Try this:
fs.readFile(__dirname + '/../../foo.bar');
Note the forward slash at the beginning of the relative path.
Use path.join http://nodejs.org/docs/v0.4.10/api/path.html#path.join
var path = require("path"),
fs = require("fs");
fs.readFile(path.join(__dirname, '../..', 'foo.bar'));
path.join() will handle leading/trailing slashes for you and just do the right thing and you don't have to try to remember when trailing slashes exist and when they dont.