CODEWITHSUNDEEP
javascriptnode.jsstreamcommand-line-interface
n370
n370

Reputation: 3617

Node's process.stdin readable stream logs Null when read inside a readable event listener callback

Without making use of a data event, I want this code to log the unicode reference of each key as I press it down. I can't understand why I'm getting Null everytime.

Whenever I press down a key on my keyboard I'll fire a readable event on process.stdin running a callback which allows me to read data from this readable stream. So why it isn't holding any data from my keypresses?

// nodo.js

function nodo() { 
  var stdin = process.stdin;
  var stdout = process.stdout;

  if (stdin.isTTY) {
    stdin.setRawMode(true);
    stdin.setEncoding('utf8');
    stdin.resume();
    stdout.write('\u000A>Bienvenido\u000A');      
  } else {
    process.exit();
  }

  stdin.on('readable', function(){

    var input = stdin.read();
    console.log(input);

  });
}

nodo();

running the code

I appreciate your attention.

Upvotes: 2

Views: 1916

Answers (1)

zmo
zmo

Reputation: 24812

Please have a read of that document that explains how to correctly handle process.stdin. Your mistake was to use stdin.resume that enables the "old" compatibility mode on process stdin streams.

// nodo.js

function nodo() { 
    var stdin = process.stdin;
    var stdout = process.stdout;

    if (stdin.isTTY) {
        stdin.setRawMode(true);
        stdin.setEncoding('utf8');
        stdout.write('\u000A>Bienvenido\u000A');      

        process.stdin.setEncoding('utf8');

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

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

nodo();

Upvotes: 1

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