add shell.sudoDetached()

src/shell.js

@@ -1,9 +1,10 @@
 'use strict';
 
 exports = module.exports = {
-    sudo: sudo,
     exec: exec,
-    execSync: execSync
+    execSync: execSync,
+    sudo: sudo,
+    sudoDetached: sudoDetached
 };
 
 var assert = require('assert'),
@@ -71,3 +72,34 @@ function sudo(tag, args, callback) {
     cp.stdin.end();
 }
 
+function sudoDetached(tag, args, callback) {
+    assert.strictEqual(typeof tag, 'string');
+    assert(util.isArray(args));
+    assert.strictEqual(typeof callback, 'function');
+
+    callback = once(callback); // exit may or may not be called after an 'error'
+
+    debug(tag + ' sudoDetached: %s %s', SUDO, args.join(' '));
+
+    var cp = child_process.spawn(SUDO, [ '-S' ].concat(args), { detached: true });
+    cp.stdout.on('data', function (data) {
+        debug(tag + ' (stdout): %s', data.toString('utf8'));
+    });
+
+    cp.stderr.on('data', function (data) {
+        debug(tag + ' (stderr): %s', data.toString('utf8'));
+    });
+
+    cp.on('exit', function (code, signal) {
+        if (code || signal) debug(tag + ' code: %s, signal: %s', code, signal);
+
+        callback(code === 0 ? null : new Error(util.format(tag + ' exited with error %s signal %s', code, signal)));
+    });
+
+    cp.on('error', function (error) {
+        debug(tag + ' code: %s, signal: %s', error.code, error.signal);
+        callback(error);
+    });
+
+    return cp;
+}