node.js - Promise.promisify get parameters from position 2..n in then resolution -

the first time posted confused actual issue was. in bluebird documentation promisify, says

the node function should conform node.js convention of accepting callback last argument , calling callback error first argument , success value on second argument.

this means parameter in 1st position (error) passed .catch. parameter in 2nd position passed .then. if there more 1 "success" value, how capture parameters 3rd position , on? child_process.exec callback function called function (error, stdout, stderr). there anyway capture stderr in promisify'd function? this

var promise = require('bluebird'); var child_process = promise.promisifyall(require('child_process'));  var execasync = child_process.execasync; var exec = child_process.exec;  // normal callback, can access stderr exec('node-gyp rebuild', function(error, stdout, stderr) {     console.log(stderr); });  execasync('node-gyp rebuild') .then(function(stdout, stderr) {     console.log(stderr);     // > undefined }) .catch(function(error) {     // });