This gist shows how to fork a nodejs stream into 2 streams

forkStream.js

var spawn = require('child_process').spawn;
var pass = require('stream').PassThrough;

var a = spawn('echo', ['hi user']);
var b = new pass;
var c = new pass;

a.stdout.pipe(b);
a.stdout.pipe(c);

var count = 0;
b.on('data', function(chunk) { count += chunk.length; });
b.on('end', function() { console.log('b stream : ' + count); });

var data = '';
c.on('data', function(chunk) { data += chunk; });
c.on('end', function() { console.log('c stream : ' +data); });