How to run multiple LESS tasks with GruntJS Watch? -

i have following gruntfile.js. bootstrap.less file has tons of imports includes plugins' css codes well. therefore, bootstrap takes 5-20 seconds compile whenever make change less files. there way can have 2 different less tasks, whenever there's change in of bootstrap's imported files, runs less task associated bootstrap , other task run if main.less changed.

module.exports = function(grunt) {    // project configuration.   grunt.initconfig({     pkg: grunt.file.readjson('package.json'),      less: {       development: {         options: {           paths: ["../css"]         },         files: {           "../css/bootstrap.css": "../less/bootstrap.less",           "../css/main.css": "../less/main.less"         }       }     },     watch: {       options: {         livereload: true       },       less: {         options: {           livereload: false,           spawn: false         },         files: ['../less/*.less', '../less/responsive/*.less'],         tasks: ['less']       }, css: {           files: ['../css/main.css'],           tasks: []       }        }   });    // less   grunt.loadnpmtasks('grunt-contrib-less');    // watch   grunt.loadnpmtasks('grunt-contrib-watch');  }; 

try running code :

module.exports = function(grunt) {    // project configuration.   grunt.initconfig({     pkg: grunt.file.readjson('package.json'),      less: {       development: {         options: {           paths: ["../css"]         },         files: {           "../css/main.css": "../less/main.less"         }       },       bootstrapbuild : {         options : {           paths: ['../css']         },         files : {           "../css/bootstrap.css": "../less/bootstrap.less",                   }       }     },     watch: {       options: {         livereload: true       },       maincss: {         options: {           livereload: false,           spawn: false         },         files: ['../less/*.less', '../less/responsive/*.less', '!../less/bootstrap.less'],         tasks: ['less: development']       },        bootstrapbuild : {         files: ['../less/bootstrap.less'],         tasks: ['less:bootstrapbuild']       },       css: {           files: ['../css/main.css'],           tasks: []       }        }   });    // less   grunt.loadnpmtasks('grunt-contrib-less');    // watch   grunt.loadnpmtasks('grunt-contrib-watch');  };