Run Grunt tasks with only those source files modified since the last successful run.
Last updated 3 years ago by tschaub .
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$ cnpm install grunt-newer 
SYNC missed versions from official npm registry.


Configure Grunt tasks to run with newer files only.

Synopsis: The newer task will configure another task to run with src files that are a) newer than the dest files or b) newer than the last successful run (if there are no dest files). See below for examples and more detail.

Getting Started

This plugin requires Grunt ~0.4.1

If you haven't used Grunt before, be sure to check out the Getting Started guide, as it explains how to create a gruntfile.js as well as install and use Grunt plugins. Once you're familiar with that process, you may install this plugin with this command:

npm install grunt-newer --save-dev

Once the plugin has been installed, it may be enabled inside your gruntfile.js with this line:


The newer task

The newer task doesn't require any special configuration. To use it, just add newer as the first argument when running other tasks.

For example, if you want to use Uglify to minify your source files only when one or more of them is newer than the previously minified destination file, configure the uglify task as you would otherwise, and then register a task with newer at the front.

    uglify: {
      all: {
        files: {
          'dest/app.min.js': ['src/**/*.js']


  grunt.registerTask('minify', ['newer:uglify:all']);

With the above configuration the minify task will only run uglify if one or more of the src/**/*.js files is newer than the dest/app.min.js file.

The above example shows how the newer task works with other tasks that specify both src and dest files. In this case, the modification time of src files are compared to modification times of corresponding dest files to determine which src files to include.

The newer task can also be used with tasks that don't generate any dest files. In this case, newer will only use files that are newer than the last successful run of the same task.

For example, if you want to run JSHint on only those files that have been modified since the last successful run, configure the jshint task as you would otherwise, and then register a task with newer at the front.

    jshint: {
      all: {
        src: 'src/**/*.js'


  grunt.registerTask('lint', ['newer:jshint:all']);

With the above configuration, running grunt lint will configure your jshint:all task to use only files in the jshint.all.src config that have been modified since the last successful run of the same task. The first time the jshint:newer:all task runs, all source files will be used. After that, only the files you modify will be run through the linter.

Another example is to use the newer task in conjunction with watch. For example, you might want to set up a watch to run a linter on all your .js files whenever one changes. With the newer task, instead of re-running the linter on all files, you only need to run it on the files that changed.

  var srcFiles = 'src/**/*.js';

    jshint: {
      all: {
        src: srcFiles
    watch: {
      all: {
        files: srcFiles,
        tasks: ['newer:jshint:all']


With the above configuration, running grunt jshint watch will first lint all your files with jshint and then set up a watch. Whenever one of your source files changes, the jshint task will be run on just the modified file.

Note: If your task is configured with dest files, newer will run your task with only those files that are newer than the corresponding dest files.

Options for the newer task

In most cases, you shouldn't need to add any special configuration for the newer task. Just grunt.loadNpmTasks('grunt-newer') and you can use newer as a prefix to your other tasks. The options below are available for advanced usage.


  • type: string
  • default: node_modules/grunt-newer/.cache

To keep track of timestamps for successful runs, the newer task writes to a cache directory. The default is to use a .cache directory within the grunt-newer installation directory. If you need timestamp info to be written to a different location, configure the task with a cache option.

Example use of the cache option:

    newer: {
      options: {
        cache: 'path/to/custom/cache/directory'


  • type: function(Object, function(boolean))
  • default: null

The newer task determines which files to include for a specific task based on file modification time. There are occassions where you may want to include a file even if it has not been modified. For example, if a LESS file imports some other files, you will want to include it if any of the imports have been modified. To support this, you can provide an override function that takes two arguments:

  • details - Object
    • task - string The currently running task name.
    • target - string The currently running target name.
    • path - string The path to a src file that appears to be "older" (not modified since the time below).
    • time - Date The comparison time. For tasks with dest files, this is the modification time of the dest file. For tasks without dest files, this is the last successful run time of the same task.
  • include - function(boolean) A callback that determines whether this src file should be included. Call with true to include or false to exclude the file.

Example use of the override option:

    newer: {
      options: {
        override: function(detail, include) {
          if (detail.task === 'less') {
            checkForModifiedImports(detail.path, detail.time, include);
          } else {


  • type: number (milliseconds)
  • default: 0

The newer tasks compares the file modification times of the source and destination files with millisecond precision. On some file systems this causes destination files to always be considered older because of imprecision in the registration of modification times.

If your tasks are always run even though the source files are not modified use the tolerance option to compensate for this imprecision.

In most cases setting the option to 1000 milliseconds should be enough. If the file system is very imprecise use a higher value.

Example use of the tolerance option:

    newer: {
      options: {
        tolerance: 1000

That's it

Please submit an issue if you encounter any trouble. Contributions or suggestions for improvements welcome!

Current Status

Known limitations

The newer task relies on Grunt's convention for specifying src/dest mappings. So it should be expected to work with two types of tasks:

  1. Tasks that specify both src and dest files. In this case, the task prefixed by newer will be configured to run with src files that are newer than the corresponding dest file (based on the mtime of files).

  2. Tasks that specify only src files. In this case, the task prefixed by newer will be configured to run with src files that are newer than the previous successful run of the same task.

The newer task will not work as a prefix for the following tasks:

  • grunt-rsync - Though this task specifies src and dest files, the dest file is not generated based on src files (instead it is a directory).

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