Example Gulpfile

gulpfile.js

gulp.task('sass', function () {
  gulp.src('app/styles/**/*.scss')
    .pipe(sass())
    .pipe(autoprefixer('last 1 version'))
    .pipe(gulp.dest('dist/styles'));
});

gulp.task('default', function() {
  gulp.run('sass');
  gulp.watch('app/styles/**/*.scss', function() {
    gulp.run('sass');
  });
});