grunt-contrib-watch/docs/watch-options.md

Settings

There are a number of options available. Please review the minimatch options here. As well as some additional options as follows:

files

Type: String|Array

This defines what file patterns this task will watch. Can be a string or an array of files and/or minimatch patterns.

tasks

Type: String|Array

This defines which tasks to run when a watched file event occurs.

options.nospawn

Type: Boolean Default: false

This instructs the watch task to not spawn task runs in a child process. Setting this option also speeds up the reaction time of the watch (usually 500ms faster for most) and allows subsequent task runs to share the same context (i.e., using a reload task). Not spawning task runs can make the watch more prone to failing so please use as needed.

Example:

watch: {
  scripts: {
    files: ['**/*.js'],
    tasks: ['livereload'],
    options: {
      nospawn: true,
    },
  },
},

options.interrupt

Type: Boolean Default: false

As files are modified this watch task will spawn tasks in child processes. The default behavior will only spawn a new child process per target when the previous process has finished. Set the interrupt option to true to terminate the previous process and spawn a new one upon later changes.

Example:

watch: {
  scripts: {
    files: '**/*.js',
    tasks: ['jshint'],
    options: {
      interrupt: true,
    },
  },
},

options.debounceDelay

Type: Integer Default: 500

How long to wait before emitting events in succession for the same filepath and status. For example if your Gruntfile.js file was changed, a changed event will only fire again after the given milliseconds.

Example:

watch: {
  scripts: {
    files: '**/*.js',
    tasks: ['jshint'],
    options: {
      debounceDelay: 250,
    },
  },
},

options.interval

Type: Integer Default: 100

The interval is passed to fs.watchFile. Since interval is only used by fs.watchFile and this watcher also uses fs.watch; it is recommended to ignore this option. Default is 100ms.

options.event

Type: String|Array Default: 'all'

Specify the type watch event that trigger the specified task. This option can be one or many of: 'all', 'changed', 'added' and 'deleted'.

Example:

watch: {
  scripts: {
    files: '**/*.js',
    tasks: ['generateFileManifest'],
    options: {
      event: ['added', 'deleted'],
    },
  },
},

options.forever

Type: Boolean Default: true

This is only a task level option and cannot be configured per target. By default the watch task will duck punch grunt.fatal and grunt.warn to try and prevent them from exiting the watch process. If you don't want grunt.fatal and grunt.warn to be overridden set the forever option to false.

options.atBegin

Type: Boolean Default: false

This option will trigger the run of each specified task at startup of the watcher.

options.livereload

Type: Boolean|Number|Object Default: false

Set to true or set livereload: 1337 to a port number to enable live reloading. Default and recommended port is 35729.

If enabled a live reload server will be started with the watch task per target. Then after the indicated tasks have ran, the live reload server will be triggered with the modified files.

Example:

watch: {
  css: {
    files: '**/*.sass',
    tasks: ['sass'],
    options: {
      livereload: true,
    },
  },
},