The problem with installing the gem that way is that you're shelling out to another process with:

`gem install rubyzip`

and after that finishes installing the gem, your current irb session still won't see it. You'd have to reload irb with exec "irb" and then calling require 'zip' again.

Note: those are backticks not single quotes.

Try this:

begin require 'zip' rescue LoadError `gem install rubyzip` exec "irb" retry end

For me require 'zip' works. I have rubyzip-1.1.2

Now you should be able to use Zip