Stream example

foo.js

var fs = require('fs')

function cat(file) {
  var stream = fs.createReadStream(file)
  stream.setEncoding('utf8')
  return function(write){
    stream.on('error', write)
    stream.on('data', function(d){ write(null, d) })
    stream.on('end', write)
  }
}

function uppercase(read) {
  return function(write){
    read(function(err, str){
      if (err) write(err)
      else if (str) write(null, str.toUpperCase())
      else write()
    })
  }
}

function buffer(read) {
  var buf = ''
  return function(write){
    read(function(err, str){
      if (err) write(err)
      else if (str) buf += str
      else write(null, buf)
    })
  }
}

var read = buffer(uppercase(cat('petss.txt')))

read(function(err, buf){
  if (err) {
    console.error(err.stack);
  } else {
    console.log(buf);
  }
})

hmm yeah looks kinda lame with error propagation