gistfile1.js

// works
var fs = require('fs'),
     spawn = require('child_process').spawn,
     out = fs.openSync('./out.log', 'a'),
     err = fs.openSync('./out.log', 'a');

 var child = spawn('prg', [], {
   detached: true,
   stdio: [ 'ignore', out, err ]
 });

 child.unref();

// stderr doesn't seem to get written out
var fs = require('fs'),
     spawn = require('child_process').spawn,
     out = fs.openSync('./out.log', 'a');

 var child = spawn('prg', [], {
   detached: true,
   stdio: [ 'ignore', out, out ]
 });

 child.unref();