grunt-contrib-watch/README.md

# grunt-contrib-watch [![Build Status](https://secure.travis-ci.org/gruntjs/grunt-contrib-watch.png?branch=master)](http://travis-ci.org/gruntjs/grunt-contrib-watch)

> Run predefined tasks whenever watched file patterns are added, changed or deleted.

## Getting Started
Install this grunt plugin next to your project's [grunt.js gruntfile][getting_started] with: `npm install grunt-contrib-watch`

Then add this line to your project's `Gruntfile.js` gruntfile:

```javascript
grunt.loadNpmTasks('grunt-contrib-watch');
```

[grunt]: https://github.com/gruntjs/grunt
[getting_started]: https://github.com/gruntjs/grunt/blob/master/docs/getting_started.md

### Overview

Inside your `Gruntfile.js` file, add a section named `watch`. This section specifies the files to watch, tasks to run when an event occurs and the options used.

##### files ```string|array```

This defines what file patterns this task will watch. Can be a string or an array of files and/or [minimatch](https://github.com/isaacs/minimatch) patterns.

##### tasks ```string|array```

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

##### options ```array```

This controls how this task operates and should contain key:value pairs, see options below.

#### Options

There are a number of options available. Please review the [minimatch options here](https://github.com/isaacs/minimatch#options). As well as some additional options as follows:

##### interrupt ```boolean```

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

##### debounceDelay ```integer```

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. *Default is 500ms.*

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

##### interval ```integer```

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*.

#### Config Examples

``` javascript
// Simple config to run jshint any time a file is added, changed or deleted
grunt.initConfig({
  watch: {
    files: '**/*',
    tasks: ['jshint']
  }
});
```

``` javascript
// Advanced config. Run specific tasks when specific files are added, changed or deleted.
grunt.initConfig({
  watch: {
    gruntfile: {
      files: 'Gruntfile.js',
      tasks: ['jshint:gruntfile'],
      options: {
        nocase: true
      }
    },
    src: {
      files: ['lib/*.js', 'css/**/*.scss', '!lib/dontwatch.js'],
      tasks: ['default']
    },
    test: {
      files: '<%= jshint.test.src %>',
      tasks: ['jshint:test', 'qunit']
    }
  }
});
```