Minifying CSS

Using gulp-clean-css and gulp-rename

First, Install gulp, gulp-clean-css and gulp-rename to project directory localy

npm install --save-dev gulp gulp-clean-css gulp-rename

Than add following minify-css task to your gulpfile.js

var gulp = require('gulp');
var cleanCSS = require('gulp-clean-css');
var rename = require('gulp-rename');

gulp.task('minify-css', function() {
    return gulp.src('css/dist/dist.css')
        .pipe(cleanCSS())
        .pipe(rename('dist.min.css'))
        .pipe(gulp.dest('css/dist'));
});

gulp.task('watch', function(){
  gulp.watch('css/dist/**/*.css', ['minify-css']); 
  // Other watchers
});

gulp.task('default', ['minify-css', 'watch']);

Here .pipe(cleanCSS()) executes minification of your css/dist/dist.css file and .pipe(rename('concat.min.css')) renames it to dist.min.css

Sass and Css - Preprocessing with Gulp

Before starting gulp we need to install node.js and npm. Then install gulp-sacc

$ npm i gulp-sass --save-dev // i = install

Gulp Head

var gulp = require('gulp');
// Requires the gulp-sass plugin
var sass = require('gulp-sass');

Gulp Body

gulp.task('sass', function(){
  return gulp.src('app/scss/*.scss') // searching for sass files
    .pipe(sass()) // Converts Sass to CSS with gulp-sass
    .pipe(gulp.dest('app/css')) // destination of the css file
});

Gulp watch

gulp.task('watch', function(){
  gulp.watch('app/scss/**/*.scss', ['sass']); 
  // Other watchers
})