Here's an example Gulpfile that compiles Sass files and minifies CSS

gulpfile.js

//Compiles Sass files and minifies CSS

const gulp = require('gulp');
const sass = require('gulp-sass');
const cleanCSS = require('gulp-clean-css');

gulp.task('sass', function () {
  return gulp.src('src/scss/**/*.scss')
    .pipe(sass().on('error', sass.logError))
    .pipe(cleanCSS())
    .pipe(gulp.dest('dist/css'));
});

gulp.task('watch', function () {
  gulp.watch('src/scss/**/*.scss', gulp.series('sass'));
});

gulp.task('default', gulp.series('sass', 'watch'));