PostCSS Gulp

Gulpfile.js

'use strict';

var gulp = require('gulp');
var postcss = require('gulp-postcss');

gulp.task('styles', function () {
  var opts = {
    basePath: 'input/',
    maps: [ 'whatever.yml' ],
  };

  var processors = [
    require('postcss-map')(opts),
    require('autoprefixer-core')(),
  ];
  
  return gulp.src('input/**/*.css')
    .pipe(postcss(processors))
    .pipe(gulp.dest('output'));
});