Spawn now minimally works. Busybox can invoke "ls".

boot-worker.js

@@ -1,8 +1,11 @@
 importScripts('jspm_packages/system.js', 'config.js');
 
-var main;
-
-System.import('js/worker.js').then(function (m) {
-    main = m;
-    importScripts('bin/busybox');
+var Module;
+addEventListener('message', function (e) {
+    if (!e.isTrusted || Module)
+        return;
+    Module = {};
+    System.import('js/worker.js').then(function (m) {
+        m.start(Module, e.data);
+    });
 });

js/build-busybox

@@ -2,7 +2,7 @@
 mkdir -p bin
 
 export CFLAGS="-include `readlink -f runtime/em-shell.h` -g"
-export EM_LDFLAGS="--pre-js ../em-shell/js/pre.js --js-opts 0 `readlink -f runtime/em-shell.c` --js-library `readlink -f runtime/em-shell.js`"
+export EM_LDFLAGS="--js-opts 0 `readlink -f runtime/em-shell.c` --js-library `readlink -f runtime/em-shell.js`"
 export KBUILD_VERBOSE=1
 export ARCH=em 
 export CROSS_COMPILE=em

js/console.js

@@ -62,6 +62,11 @@ function startService() {
     }
 }
 
+function spawn(file, args) {
+    let w = new Worker("boot-worker.js");
+    w.postMessage({file: file, args: args});
+}
+
 function serviceConnected() {
     log('Connecting console to service');
 
@@ -79,15 +84,17 @@ function serviceConnected() {
         if (e.data.command == 'writeConsole')
             term.write(e.data.msg.replace('\n', '\r\n'));
         else if(e.data.command == 'spawn') {
-            e.data.port.postMessage(9);
+            spawn('/bin/busybox', e.data.args); // TODO: process e.data.file
+            e.data.port.postMessage(0); // TODO: report real status
         }
     };
+
     navigator.serviceWorker.controller.postMessage({
         'command': 'setMasterPort',
         'port': messageChannel.port2}, 
         [messageChannel.port2]);
 
-    new Worker("boot-worker.js");
+    spawn('/bin/busybox', ['/bin/sh']);
 }
 
 term.open(document.getElementById('console'));

js/worker.js

@@ -14,12 +14,37 @@ function syncPost(url, data) {
     req.send(data);
 }
 
-export function print(x) {
+function print(x) {
     syncPost('service/writeConsole', x);
 }
 
-export function stdin() {
+function stdin() {
     return syncGet('service/readConsole');
 }
 
-print('Worker started\r\n');
+let Module;
+export function start(m, msg) {
+    Module = m;
+    Module.thisProgram = msg.args.shift();
+    Module.arguments = msg.args;
+    Module.print = print;
+    Module.printErr = print;
+    Module.preInit = () => {
+        TTY.ttys[FS.makedev(5, 0)].ops = {
+            get_char: tty => {
+                if (!tty.input.length) {
+                    var result = stdin();
+                    if (!result)
+                        return null;
+                    tty.input = intArrayFromString(result, true);
+                }
+                return tty.input.shift();
+            }, put_char: (tty, val) => {
+                print(String.fromCharCode(val));
+            }, flush: tty => {
+            }
+        };
+    };
+
+    importScripts(msg.file);
+}