node.js: readSync from stdin?


Question

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:

fs:189
  var r = binding.read(fd, 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
1
51
8/7/2010 3:24:50 PM

Accepted Answer

I've no idea when this showed up but this is a helpful step forward: http://nodejs.org/api/readline.html

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.

19
1/25/2013 1:11:12 AM

Have you tried:

fs=require('fs');
console.log(fs.readFileSync('/dev/stdin').toString());

However, it will wait for the ENTIRE file to be read in, and won't return on \n like scanf or cin.


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