node.js: readSync from stdin? Code Answer

Is it possible to synchronously read from stdin in node.js? Because I’m writing a brainfuck to JavaScript compiler in JavaScript (just for fun). Brainfuck supports a read operation which needs to be implemented synchronously.

I tried this:

const fs = require('fs');
var c = fs.readSync(0,1,null,'utf-8');
console.log('character: '+c+' ('+c.charCodeAt(0)+')');

But this only produces this output:

  var r =, buffer, offset, length, position);
Error: EAGAIN, Resource temporarily unavailable
    at Object.readSync (fs:189:19)
    at Object.<anonymous> (/home/.../stdin.js:3:12)
    at Module._compile (module:426:23)
    at Module._loadScriptSync (module:436:8)
    at Module.loadSync (module:306:10)
    at Object.runMain (module:490:22)
    at node.js:254:10


I’ve no idea when this showed up but this is a helpful step forward:

var readline = require('readline');

var rl = readline.createInterface({
  input: process.stdin,
  output: process.stdout,
  terminal: false

rl.on('line', function (cmd) {
  console.log('You just typed: '+cmd);

Now I can read line-at-a-time from stdin. Happy days.

Related Posts

© No Copyrights, All Questions are retrived from public domain.
Tutorial Guruji