lazy_stream.js

// In this example, I want to create a stream that pipes a file through a
// transform, *without* beginning to read data from the file. I want the
// whole pipeline to be lazy until I call read() on the end of the pipeline.
// 
// Instead, the console.log() call fires unexpectedly.

var fs     = require('fs'),
    stream = require('stream');

var dest = new stream.Transform({highWaterMark:0});
dest._transform = function(chunk, encoding, callback) {
  console.log(chunk);
};

var result = fs.createReadStream('./foo.txt').pipe(dest);