What Is Angular CLI?
Angular cli is a command line interface to scaffold and build angular apps using nodejs style (commonJs) modules.
Not only it provides you scalable project structure, instead, it handles all common tedious tasks for you out of the box.
How To Updating Angular CLI? How to Update to Angular 5?
In order to update the angular-cli package installed globally in your system, you need to run:
npm uninstall -g angular-cli
npm cache clean
npm install -g @angular/cli@latest
Depending on your system, you may need to prefix the above commands with sudo.
Also, most likely you want to also update your local project version because inside your project directory it will be selected with higher priority than the global one:
rm -rf node_modules
npm uninstall --save-dev angular-cli
npm install --save-dev @angular/cli@latest