Concatenates css files, bubbling up @import statements (as per the standard), and optionally rebasing urls and inlining local @import statements.

Install with npm.

npm install --save-dev gulp-concat-css

var gulp = require('gulp');
var concatCss = require('gulp-concat-css');

gulp.task('default', function () {
  return gulp.src('assets/**/*.css')
    .pipe(concatCss("styles/bundle.css"))
    .pipe(gulp.dest('out/'));
});

TIP: for a proper import inlining and url rebase, make sure you set the proper base for the input files.

concatCss(targetFile, options)

• targetFile: The relative path of the generated file containing the concatenated css
• options: (since 2.1.0)
  • inlineImports: (default true) Inline any local import statement found
  • rebaseUrls: (default true) Adjust any relative URL to the location of the target file.
  • includePaths: (default []) Include additional paths when inlining imports
  • commonBase: (default to the base property of the first file) Common base path from which files and urls resolve

MIT @ Mario Casciaro