Compute chunks size in mongodb

//works only for mongo 2.2
//works better if you use mongo-hacker (https://github.com/TylerBrock/mongo-hacker)
var ns ="products.products";
var key = {partnerId : 1, id : 1}; //the shard key of the collection
if (typeof colorize != "function") colorize = function(s) {return s};
var zeroChunk =0
var chunkSize = db.getSiblingDB("config").settings.findOne({_id : "chunksize"}).value; //target chunkSize in mb
db.getSiblingDB("config").chunks.find({ns : ns}).limit(500).forEach(function(chunk) {
        var ds = db.getSiblingDB(ns.split(".")[0]).runCommand({datasize:chunk.ns,keyPattern:key,min:chunk.min,max:chunk.max});
                if (ds.numObjects ==0)
                  zeroChunk++;
                else {
                  if (ds.size > chunkSize*1024 *1024) color = "red"; else color = "black";
          print("Chunk: "+chunk._id +" has a size of "+colorize(ds.size,color)+", and includes "+ds.numObjects+" objects (took "+ds.millis+"ms)")
                 }
    }
)
print(zeroChunk*100/db.getSiblingDB("config").chunks.find({ns : ns}).count() + " chunks were empty");