Gulp Laravel 5/Elixir execute but not create any files

Question

I have a quite simple code for Gulp to execute, but still does not get any effects. It finishes without any errors, actually there are not many code to change, and I'm stuck. Linux Mint x64, node v4.2.6, Gulp CLI & Local 3.9.1.

var elixir = require('laravel-elixir');

/*
 |--------------------------------------------------------------------------
 | Elixir Asset Management
 |--------------------------------------------------------------------------
 |
 | Elixir provides a clean, fluent API for defining some basic Gulp tasks
 | for your Laravel application. By default, we are compiling the Sass
 | file for our application, as well as publishing vendor resources.
 |
 */

elixir(function(mix) {
    mix.sass('app.scss')

    .styles([
        'libs/blog-post.css',
        'libs/bootstrap.css',
        'libs/font-awesome.css',
        'libs/metisMenu.css',
        'libs/sb-admin-2.css',
        'libs/styles.css'
    ], '/public/css/libs.css')

        .scripts([
            'libs/bootstrap.js',
            'libs/jquery.js',
            'libs/metisMenu.js',
            'libs/sb-admin-2.js',
            'libs/scripts.js'
        ], '/public/js/libs.js');

});


[02:51:41] Using gulpfile /opt/lampp/htdocs/laravel-application/gulpfile.js
[02:51:41] Starting 'default'...
[02:51:41] Starting 'sass'...

Fetching Sass Source Files...
   - resources/assets/sass/app.scss


Saving To...
   - public/css/app.css

[02:51:44] Finished 'default' after 2.65 s
[02:51:44] gulp-notify: [Laravel Elixir] Sass Compiled!
[02:51:44] Finished 'sass' after 2.83 s
[02:51:44] Starting 'styles'...

Fetching Styles Source Files...
   - resources/assets/css/libs/blog-post.css
   - resources/assets/css/libs/bootstrap.css
   - resources/assets/css/libs/font-awesome.css
   - resources/assets/css/libs/metisMenu.css
   - resources/assets/css/libs/sb-admin-2.css
   - resources/assets/css/libs/styles.css


Saving To...
   - /public/css/libs.css

[02:51:44] gulp-notify: [Laravel Elixir] Stylesheets Merged!
[02:51:44] Finished 'styles' after 140 ms
[02:51:44] Starting 'scripts'...

Fetching Scripts Source Files...
   - resources/assets/js/libs/bootstrap.js
   - resources/assets/js/libs/jquery.js
   - resources/assets/js/libs/metisMenu.js
   - resources/assets/js/libs/sb-admin-2.js
   - resources/assets/js/libs/scripts.js


Saving To...
   - /public/js/libs.js

[02:51:45] gulp-notify: [Laravel Elixir] Scripts Merged!
[02:51:45] Finished 'scripts' after 581 ms