In some instances you want to install a module globally, so that it can be used from any directory. For example, the Grunt or Gulp build tools are widely useful, and conceivably you will find it useful if these tools are installed globally. Simply add the -g option:
$ npm install -g grunt-cli
If you get an error, and you're on a Unix-like system (Linux/Mac), you may need to run this with sudo:
$ sudo npm install -g grunt-cli
A global install is most important for those packages which install executable commands. We'll get into this shortly.
If a local package install lands in node_modules, where does a global package install land? On a Unix-like system it lands in PREFIX/lib/node_modules, and on Windows it lands ...
