Question

I am on Ubuntu10

sudo apt-get install ruby1.9.1-full

then download sources of rubygem 1.3.7 and install it

sudo ruby setup.rb

then, for example, install sinatra

sudo gem install sinatra

Finally open irb and type

require "rubygems"
require "sinatra"

and get error

LoadError: no such file to load -- sinatra
    from (irb):2:in `require'
    from (irb):2
    from /usr/bin/irb:12:in `<main>'

Answer 1

I had exactly this problem. The problem is that gem and ruby disagree about where the gems live. Compare these:

ruby -e "puts Gem.path"

gem env

gem which sinatra

If you’re like my setup, you’ll notice that there’s an entry in gem env’s paths that isn’t in Gem.path, and that’s exactly where sinatra will claim to be. In my case, I had to add

export GEM_HOME=/usr/lib/ruby/gems/1.9.1

to my .profile. Then everyone was happy.