How to handle input? (scanf)

[epiqueras]

I have some code that looks like this:

repl.evaluate(
  '#include <stdio.h> \n int main() { printf("hello world"); int n = 0; scanf("%d", &n); printf("hello world"); return 0; }',
   {    
    stdout: function(str) {
      commandLine.append(str + '\n')
    }
   }
).then(function(result) {
    commandLine.append((result.error || result.data) + '\n');
  }, function(err) {
    commandLine.append(err + '\n');
  }
);

iText.keyup(function(e){
  if(e.keyCode == 13) {
    console.log(iText.val());
    iText.val('');
    repl.write(iText.val() + '\n');
  }
});

Without scanf it prints both "hello world"s.

With scanf I would except it to print the first one, wait for an input, and then print the second one. Instead, it doesn't print anything and it doesn't return any errors either. It lets me enter inputs (doesn't give the "you must evaluate before writing" error), but it doesn't return anything.