gulpfile.js

// Include gulp
var gulp      = require('gulp');

// Include plugins
var watch     = require('gulp-watch');
var plumber   = require('gulp-plumber');
var sass      = require('gulp-sass');
var prefix    = require('gulp-autoprefixer');
var minifycss = require('gulp-minify-css');
var rename    = require('gulp-rename');
var debug     = require('gulp-debug');



// Process Sass (compile, prefix, minify)
gulp.task('sass', function() {
    watch({ glob: 'sass/**/*.{scss,sass}', name: 'sass-watch'})
        // Keeps pipes working after error event
        .pipe(plumber())

        // Process Sass files
        .pipe(sass())

        // Prefix CSS properties
        .pipe(prefix('last 2 version', "> 1%", 'ie 9', 'ie 8'))

        .pipe(debug({verbose: true}))

        // Output regular `*.css`
        .pipe(gulp.dest('css'))

        // Minify CSS
        .pipe(minifycss())

        // Append `.min` to filename
        .pipe(rename({suffix: '.min'}))

        .pipe(debug({verbose: true}))

        // Output minified `*.min.css`
        .pipe(gulp.dest('css'));
});



// Default task is simply called with `gulp`, 'sass-watch'
gulp.task('default', ['sass']);