GRUNT TASK

Gruntfile-copy-file.js

module.exports = function(grunt){
    grunt.initConfig({
        copy:{
            css:{
                files:[
                    {
                        cwd: 'folder/source/file',
                        src: '**/*.css',
                        dest: 'folder/target/',
                        expand: true
                    }
                ]
            }
        },

        watch:{
            options: {
                spawn: false,
                cwd: 'folder/yg/di/watch/'
            },
            css: {
                files: ['**/*.*'],
                tasks: ['newer:copy:css']
            }
        }

    });

    grunt.loadNpmTasks('grunt-contrib-copy');
    grunt.loadNpmTasks('grunt-contrib-watch');
    grunt.loadNpmTasks('grunt-newer');

    grunt.registerTask('build', ['watch:css']);
};

Gruntfile-sass-watch.js

module.exports = function(grunt) {
	grunt.initConfig({
		pkg: grunt.file.readJSON('package.json'),
    sass: {
      dist: {
        options: {
		sourcemap: 'file',
		style: 'expanded'
        },
        files: [{
          expand: true,
          cwd: 'source/folder',
          src: ['**/*.scss'],
          dest: 'destination/folder',
          ext: '.css'
      	}]
      }
    },
	postcss: {
		 options: {
			 map: true,
			 processors: [
		 	 			require('autoprefixer')({
					 	browsers: ['last 2 versions']
				 		})
	 			]
		 	},
		 	dist: {
			 	src: 'destination/file'
		 	}
	 },
	 cssmin: {
	   target: {
	     files: [{
	       expand: true,
	       cwd: 'source/folder',
	       src: ['*.css', '!*.min.css'],
	       dest: 'destination/folder',
	       ext: '.min.css'
	     }]
	   }
	 },
	 watch: {
			css: {
				files: '**/*.scss',
				tasks: ['sass','postcss','cssmin']
			}
	}
	});
	grunt.loadNpmTasks('grunt-contrib-sass');
	grunt.loadNpmTasks('grunt-postcss');
	grunt.loadNpmTasks('grunt-contrib-cssmin');
	grunt.loadNpmTasks('grunt-contrib-watch');
	grunt.registerTask('default',['watch']);
}