First Gulpfile

gulpfile.js

var gulp = require("gulp");
var minifycss = require('gulp-minify-css');
var autoprefixer = require('gulp-autoprefixer');
var notify = require('gulp-notify');
var sass = require('gulp-ruby-sass');
var imagemin = require('gulp-imagemin');
var cache = require('gulp-cache');

gulp.task('css', function() {
  return gulp.src('sass/style.scss')
    .pipe(sass({ style: 'expanded', loadPath: ['sass/partials'] }))
    .pipe(autoprefixer('last 2 version', 'safari 5', 'ie 8', 'ie 9', 'opera 12.1', 'ios 6', 'android 4'))
    .pipe(gulp.dest('css/build/prefixed/'))
    .pipe(minifycss())
    .pipe(gulp.dest('css/build/minified/'))
    .pipe(notify({ message: 'CSS task complete' }));
});

gulp.task('images', function() {
  return gulp.src('images/**/*')
    .pipe(cache(imagemin({ optimizationLevel: 5, progressive: true, interlaced: true })))
    .pipe(gulp.dest('images/'))
    .pipe(notify({ message: 'Images task complete' }));
});


gulp.task('default', function() {
    gulp.run('css', 'images');
});


gulp.task('watch', function() {

  gulp.watch('sass/**/*.scss', function() {
      gulp.run('css');
  });
  gulp.watch('images/**/*', function() {
      gulp.run('images');
  });

});