sha1-stream

var fs = require('fs')
var shastream = require('sha1-stream')

//create a new stream
var sniff = shastream.createStream('sha256')
sniff.on('digest',function(result){
  console.log(result) //a03f181dc7dedcfb577511149b8844711efdb04f
})

//pipe something into the stream
fs.createReadStream('myfile.txt').pipe(sniff)