I have Ubuntu 12.04 and I installed gnome-shell that's version is 3.4.2. Now the gnome 3.8 has been released and I would like to upgrade my gnome-shell to 3.8.
I'm afraid there is no easy way: as they say on their PPA, 3.8 will be available only for Raring. On 12.04 you can only access to GS 3.4.
I guess you'd have to compile and fight against a ton of dependency problems...
The others answers would be right if you were on Raring, of course.
I found this, but it may make your system unstable:
The way repositories are added and used on Ubuntu, is the main reason why I believe this distribution is the easiest and fastest way to give GS 3.8 a try. You basically need to add two more repos, or three if you are adventurous!
The first repository is the Gnome 3 Team repo that contains all things missing from Ubuntu’s default repositories. You should add this one before the other two and run the usual update on your system. You can do this by typing the following commands on a terminal:
sudo add-apt-repository ppa:gnome3-team/gnome3 sudo apt-get update
Then you need to add the Ricotz testing repository that contains cutting edge git versions for the shell, gtk, glib, clutter and many Gnome applications and utilities.
sudo add-apt-repository ppa:ricotz/testing sudo apt-get update
If you want to get some more latest Gnome components and risk the stability of the system even further, then you can use the Ricotz staging repository that can be correctly used only if you added the previous two.
sudo add-apt-repository ppa:ricotz/staging sudo apt-get update sudo apt-get dist-upgrade
After upgrading, you will have the latest available Gnome Shell version with many applications and utilities of the corresponding version.
Note that some will still stay in 3.6.x version at least for now.