var unzip = require('gulp-unzip')
gulp.task('filter_sample', function(){
  gulp.src("./download/bootstrap-3.1.1-dist.zip")
    .pipe(unzip())
    .pipe(gulp.dest('./tmp'))
})

var concat = require('gulp-concat')
var unzip = require('gulp-unzip')
var minimatch = require('minimatch')
gulp.task('filter_sample', function(){
  gulp.src("./download/bootstrap-3.1.1-dist.zip")
    .pipe(unzip({
      filter : function(entry){
        return minimatch(entry.path, "**/*.min.css")
      }
    }))
    .pipe(concat("bootstrap.css"))
    .pipe(gulp.dest('./tmp'))
})

gulp.task('filter_sample', function(){
  gulp.src("./download/bootstrap-3.1.1-dist.zip")
    .pipe(unzip({ keepEmpty : true }))
    //...
})