Node.js: I can't seem to capture a child process's stdout and stderr in Windows.

child-test.js

var parent = function() {
  var spawn = require('child_process').spawn;
  var child = spawn(process.execPath, [process.argv[1], 123]);
  var stdout = '';
  var stderr = '';
  child.stdout.on('data', function(buf) {
    console.log('[STR] stdout "%s"', String(buf));
    stdout += buf;
  });
  child.stderr.on('data', function(buf) {
    console.log('[STR] stderr "%s"', String(buf));
    stderr += buf;
  });
  child.on('close', function(code) {
    console.log('[END] code', code);
    console.log('[END] stdout "%s"', stdout);
    console.log('[END] stderr "%s"', stderr);
  });
};

var child = function() {
  var code = Number(process.argv[2]);

  process.stdout.write('stdout');
  process.stderr.write('stderr');

  process.exit(code);
};

if (process.argv[2]) {
  child();
} else {
  parent();
}

results.md

OS X

$ node child-test.js 
[STR] stdout "stdout"
[STR] stderr "stderr"
[END] code 123
[END] stdout "stdout"
[END] stderr "stderr"

Windows

C:\>node child-test.js
[END] code 123
[END] stdout ""
[END] stderr ""

solution.js

var parent = function() {
  var spawn = require('child_process').spawn;
  var child = spawn(process.execPath, [process.argv[1], 123]);
  var stdout = '';
  var stderr = '';
  child.stdout.on('data', function(buf) {
    console.log('[STR] stdout "%s"', String(buf));
    stdout += buf;
  });
  child.stderr.on('data', function(buf) {
    console.log('[STR] stderr "%s"', String(buf));
    stderr += buf;
  });
  child.on('close', function(code) {
    console.log('[END] code', code);
    console.log('[END] stdout "%s"', stdout);
    console.log('[END] stderr "%s"', stderr);
  });
};

var child = function() {
  var code = Number(process.argv[2]);

  process.stdout.write('stdout');
  process.stderr.write('stderr');

  exit(code);
};

// This appears to fix the problem:
// https://gist.github.com/3427357
function exit(exitCode) {
  if (process.stdout._pendingWriteReqs || process.stderr._pendingWriteReqs) {
    process.nextTick(function() {
      exit(exitCode);
    });
  } else {
    process.exit(exitCode);
  }
}

if (process.argv[2]) {
  child();
} else {
  parent();
}

Looks like someone forgot to flush!

I also encountered this problem.