gulp minify all css files to a single file
Your gulp task is missing the concat pipe.
gulp.src('src/css/**/*.css') .pipe(minifyCSS()) .pipe(autoprefixer('last 2 version', 'safari 5', 'ie 8', 'ie 9')) .pipe(concat('style.min.css')) .pipe(gulp.dest('dist/css'))Here is a very good tutorial about building with gulp:
http://www.smashingmagazine.com/2014/06/11/building-with-gulp/
I think better is used the cleancss gulp plugin.
const cleanCSS = require('gulp-clean-css'); // npm install gulp-clean-css --save-devgulp.task('css', () => {return gulp.src('assets/styles/*.css') .pipe(cleanCSS({ debug: true, compatibility: 'ie8', level: { 1: { specialComments: 0, }, }, })) .pipe(autoprefixer({ browsers: ['last 2 versions'], cascade: false })) .pipe(rename({ basename: 'main-styles', suffix: '.min', })) .pipe(gulp.dest('dist/assets/styles/'))});