How to copy file using pipe

funny-pipes.js

var copy = function(from, to, cb){  
  var fromStream = fs.createReadStream(from)
  fromStream.on('error', cb)
  var toStream = fs.createWriteStream(to)
  toStream.on('error', cb)
  fromStream.on('end', cb)
  fromStream.pipe(toStream)
}

copy('non existing file a', 'non existing dir/file b', function(err){
  console.log(err)
})

// Error will be reported twice:
//
// { [Error: ENOENT, open 'non existing file a'] errno: 34, 
//    code: 'ENOENT', path: 'non existing file a' }
// { [Error: ENOENT, open 'non existing dir/file b'] errno: 34, 
//    code: 'ENOENT', path: 'non existing dir/file b' }

With callbacks it may be something like that

var copy = function(from, to, cb){    
  var fromStream = fs.createReadStream(from, function(err){
    if(err) return cb(err)    
    var toStream = fs.createWriteStream(to, function(err){
      if(err) return cb(err)

      fromStream.on('error', cb)
      toStream.on('error', cb)
      fromStream.on('end', cb)
      fromStream.pipe(toStream)
    })    
  })  
}

With callbacks it may be something like that

var copy = function(from, to, cb){    
  var fromStream = fs.createReadStream(from, function(err){
    if(err) return cb(err)    
    var toStream = fs.createWriteStream(to, function(err){
      if(err) return cb(err)

      fromStream.on('error', cb)
      toStream.on('error', cb)
      fromStream.on('end', cb)
      fromStream.pipe(toStream)
    })    
  })  
}