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 with every line of the file.

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

var dest = new stream.Transform();

dest._transform = function(chunk, encoding, callback) {
  console.log(chunk);
  callback();
};

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