Specify an ENV configuration as a task, e.g.

grunt.registerTask('dev', ['env:dev', 'lint', 'server', 'watch']);
grunt.registerTask('build', ['env:build', 'lint', 'other:build:tasks']);

Install this grunt plugin next to your project's grunt.js gruntfile with: npm install grunt-env

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

grunt.loadNpmTasks('grunt-env');

  env : {
    options : {
 	//Shared Options Hash
    },
    dev : {
      NODE_ENV : 'development',
      DEST     : 'temp'
    },
    build : {
      NODE_ENV : 'production',
      DEST     : 'dist',
      concat   : {
        PATH     : {
          'value': 'node_modules/.bin',
          'delimiter': ':'
        }
      }
    },
    functions: {
      BY_FUNCTION: function() {
        var value = '123';
        grunt.log.writeln('setting BY_FUNCTION to ' + value);
        return value;
      }
    }
  }

You can specify environment values in INI, JSON or YAML style and load them via the src option.

  env : {
    dev : {
      src : "dev.json"
    },
    prod: {
      src: "settings.yaml"
    }
    heroku : {
      src : ".env"
    }
  }

You can specify files to read environment variables from, similar to the daemontools envdir utility.

  env : {
    dev : {
      src : ["envdir/*"],
      options: {
        envdir: true
      }
    }
  }

The following directives can be specified in the options to alter the environment in more specific ways

• add
  • This will add the variables only if they don't already exist
• replace
  • Will replace the variable with the value specified
• unshift
  • Will prepend the value to the variable specified, optionally specifying a 'delimiter'
• push
  • Same as unshift, but at the end of the value.
• concat
  • Functionally same as push, added for readability

yourtask : {
  USER : 'you',
  PATH : '/bin:/usr/bin'

  options : {
    add : {
      VERBOSE : '1' // will only be added if VERBOSE isn't already set
    },
    replace : {
      USER : 'me'
    },
    push : {
      PATH : {
        value : '~/bin',
        delimiter : ':'
      }
    },
    unshift : {
      PATH : '/sbin:'
    }
  }
}

In order to configure your tasks based on the environment, you need to define a task and use templates:

grunt.initConfig({
  env: {
    dev: {
      MY_CONST: 'a'
    },
    prod: {
      MY_CONST: 'b'
    }
  },
  myTask: {
    options: {
      myOpt: <%= MY_CONST %>
    }
  }
});

grunt.registerTask('loadconst', 'Load constants', function() {
    grunt.config('MY_CONST', process.env.MY_CONST);
});

grunt.registerTask('default', [
    'env:dev',
    'loadconst',
    'myTask'
]);

Environment variables are strings only. If you attempt to assign complex objects, they will be converted to strings.

In lieu of a formal styleguide, take care to maintain the existing coding style. Add unit tests for any new or changed functionality. Lint and test your code using grunt.

• 0.4.0 Removed automatic parse, added ability to add ini or json style src files
• 0.3.0 Automatically parses .env files now
• 0.2.1 fixed npm install
• 0.2.0 grunt 0.4.0 support, simplified
• 0.1.0 Initial release

Licensed under the Apache 2.0 license.

Jarrod Overson