Ruby environment installation (in Ubuntu 7.10)

Start learning Ruby today. The prepared book is programming ruby-2nd. To prepare an experimental environment, I want to install the ruby environment on my ubuntu.
1. Install the interpreter:

Sudo apt-Get install Ruby

2. install an instant execution tool IRB:
The result of the first installation is that the interpreter is installed, so this IRB must be installed separately. Run the following command:

Sudo apt-Get install IRB

3. install local documents:
The document is installed separately. Run the following command:

Sudo apt-Get install ri

if you are not using Ubuntu or the version you want is not provided in the source, you can visit the following website:
http://www.ruby-lang.org/
http://www.ruby-doc.org/