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 

Answer 1

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.

Answer 2

After fiddling with this for a bit, I found the answer:

process.stdin.resume(); var fs = require('fs'); var response = fs.readSync(process.stdin.fd, 100, 0, "utf8"); process.stdin.pause(); 

response will be an array with two indexes, the first being the data typed into the console and the second will be the length of the data including the newline character.

It was pretty easy to determine when you console.log(process.stdin) which enumerates all of the properties including one labeled fd which is of course the name of the first parameter for fs.readSync()

Enjoy! :D