Can't read from stdout until terminated

bash = require('child_process').spawn '/bin/bash', []
console.log 'Spawned bash as pid ' + bash.pid
bash.stdout.on 'data', (data) ->
    process.stdout.write data

I'd expect that the code above would read from bash and display to the process stdout. It doesn't. If I replace /bin/bash with /bin/bash -c /bin/ls I will get the output of ls which I'd expect. Obviously this has something to do with bash remaining open.

Any hints on how to read what bash outputs without having to have the process terminate?