Hello Ryan, thank you for your detailed answer. I still have a lot of
problems, so I will explain my approach step by step:

First, I installed the lastest version of Ruby (1.9.2-p180) by
downloading and compiling the source code on my Ubuntu virtual machine.
This install includes Gem, when I type "gem -v" I get "1.3.7". So I
tried to use this gem version to install metric_fu, and I got :

"
root@Alexis-VBox-Ubuntu:~# gem install metric_fu --http-proxy ...
ERROR:  Loading command: install (LoadError)
    no such file to load -- zlib
ERROR:  While executing gem ... (NameError)
    uninitialized constant Gem::Commands::InstallCommand
"

It turned out that I get this error simply by typing "gem help
commands"! So I downloaded the latest version of Gem (1.8.2), installed
it by typing "ruby setup.rb" (I couldn't do "gem update --system"
because I got the same error), but even after, still the same error, I
can't use RubyGems with Ruby1.9.2-p180. Is this normal? Do you have the
same problem?

So I restored my virtual machine and installed Ruby with Synaptic
Package Manager by searching "Ruby 1.9.2", it installed the "ruby1.9.1"
and the "gem1.9.1" executables, and the funniest: when I type "ruby1.9.1
-v" I get "ruby 1.9.2p0 (2010-08-18 revision 29036) [i686-linux]" and
when I type "gem1.9.1 -v" I get "1.3.7"!! No easy to follow the changes
of version!

Anyway, with these versions, gem works; so I tried to install metric_fu:

"
root@Alexis-VBox-Ubuntu:~# gem1.9.1 install metric_fu --http-proxy ...
Building native extensions.  This could take a while...
ERROR:  Error installing metric_fu:
  ERROR: Failed to build gem native extension.

/usr/bin/ruby1.9.1 extconf.rb
<internal:lib/rubygems/custom_require>:29:in `require': no such file to
load -- mkmf (LoadError)
  from <internal:lib/rubygems/custom_require>:29:in `require'
  from extconf.rb:1:in `<main>'


Gem files will remain installed in /var/lib/gems/1.9.1/gems/rcov-0.9.9
for inspection.
Results logged to
/var/lib/gems/1.9.1/gems/rcov-0.9.9/ext/rcovrt/gem_make.out
"

So I kept my cool attitude and tried to install one by one the same
packages than you:
- ruby-progressbar
- json_pure
- hirb
- churn
- Saikuro
- syntax
- metric_fu

The six first installed correctly, but for metric_fu, I got the same
error than previously.

It's obvious that I'm wrong somewhere, certainly because I'm a newbie in
Ruby and I don't yet understand everything!
So, thank you very much to help me :)

Have a good day!
Alex

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