What is the easiest method to let express know what environment I am in? E.g. I want do do the below to make a connection to redis depending on what env I am in. Can this be done from the command line?

```
app.configure('development', function(){
  app.use(express.errorHandler({ dumpExceptions: true, showStack: true }));
  var r = require("redis").createClient(6379,'127.0.0.1');
});
app.configure('production', function(){
  app.use(express.errorHandler());
  r = redis.createClient(6379,'46.137.195.230', { detect_buffers: true });
});

```