Specify env differently in execFile

Callbacks should always be the last argument.

doc/api.markdown

@@ -1048,6 +1048,7 @@ There is a second optional argument to specify several options. The default opti
     , timeout: 0
     , maxBuffer: 200*1024
     , killSignal: 'SIGKILL'
+    , env: null
     }
 
 If `timeout` is greater than 0, then it will kill the child process

lib/child_process.js

@@ -10,7 +10,7 @@ var spawn = exports.spawn = function (path, args, env, customFds) {
   return child;
 };
 
-exports.exec = function (command /*, options, callback, env */) {
+exports.exec = function (command /*, options, callback */) {
   if (arguments.length < 3) {
     return exports.execFile("/bin/sh", ["-c", command], arguments[1]);
   } else if (arguments.length < 4) {
@@ -20,24 +20,42 @@ exports.exec = function (command /*, options, callback, env */) {
   }
 };
 
-exports.execFile = function (file, args /*, options, callback, env */) {
+
+// execFile("something.sh", { env: ENV }, funciton() { })
+
+exports.execFile = function (file /* args, options, callback */) {
   var options = { encoding: 'utf8'
                 , timeout: 0
                 , maxBuffer: 200*1024
                 , killSignal: 'SIGKILL'
+                , env: null
                 };
+  var args, optionArg, callback;
 
-  var callback = (arguments.length == 5 ? arguments[3] : arguments[arguments.length-1]);
+  // Parse the parameters.
 
-  if (arguments[2] && typeof arguments[2] == 'object') {
+  if (typeof arguments[arguments.length-1] === "function") {
+    callback = arguments[arguments.length-1];
+  }
+
+  if (Array.isArray(arguments[1])) {
+    args = arguments[1];
+    if (typeof arguments[2] === 'object') optionArg = arguments[2];
+  } else {
+    args = [];
+    if (typeof arguments[1] === 'object') optionArg = arguments[1];
+  }
+
+  // Merge optionArg into options
+  if (optionArg) {
     var keys = Object.keys(options);
     for (var i = 0; i < keys.length; i++) {
       var k = keys[i];
-      if (arguments[2][k] !== undefined) options[k] = arguments[2][k];
+      if (optionArg[k] !== undefined) options[k] = optionArg[k];
     }
   }
 
-  var child = arguments[4] ? spawn(file, args, arguments[4]) : spawn(file, args);
+  var child = spawn(file, args, options.env);
   var stdout = "";
   var stderr = "";
   var killed = false;

test/simple/test-child-process-exec-env.js

@@ -5,7 +5,7 @@ success_count = 0;
 error_count = 0;
 response = "";
 
-child = exec('/usr/bin/env', [], function (err, stdout, stderr) {
+child = exec('/usr/bin/env', { env: {'HELLO' : 'WORLD'}}, function (err, stdout, stderr) {
   if (err) {
     error_count++;
     console.log('error!: ' + err.code);
@@ -16,7 +16,7 @@ child = exec('/usr/bin/env', [], function (err, stdout, stderr) {
     success_count++;
     assert.equal(true, stdout != "");
   }
-}, {'HELLO' : 'WORLD'});
+});
 
 child.stdout.setEncoding('utf8');