Connecting node.js to stdin/stdout

gistfile1.txt

// The context here is a UCI chess interface such that a Javascript chess engine running in node.js can 
// communicate with standard chess UIs like Arena and Winboard via stdin/stdout.  But the code may be 
// useful in other contexts too.

// My own UCI interface (node.js and web worker compatible) can be found here in the lozUCI class:-

// https://github.com/op12no2/lozza

// stdin

var nodefs = require('fs');

process.stdin.setEncoding('utf8');

process.stdin.on('readable', function() {
  var chunk = process.stdin.read();
  if (chunk !== null) {
    onmessage({data: chunk});
  }
});

process.stdin.on('end', function() {
  process.exit();
});

// The UCI commands are then available in data.data in onmessage().  Note that more than one command can be 
// present separated by \n and depending on OS also \r, so assume \n and filter out \r.  In my own experience 
// null commands can be present \n\n, so watch out for those too.

// stdout

var str = ''
// ... 
nodefs.writeSync(1, str + '\n');

// The use of writeSync() is so that that the PV feedback displays in chess UIs like Arena and Winboard in real time.  
// If you write using async functions it appears all at once when the best move is sent back.

// It's useful to name the capture function onmessage() because that what web workers assume, thus it can be used in 
// both web and node.js contexts.