Why can't find the library: no such file to load - ruby

Question

I'm stuck, can't find the cause, it's suppossed to be simple,
This is the error message:
require': no such file to load -- ./ip (LoadError)
It's generated by this line of code:
require './ip'
As the
require 'socket'
works and I found the two libraries:
/usr/lib/ruby/gems/1.8/gems/ruby-ip-0.9.1/lib/ip.rb
/usr/lib/ruby/gems/1.8/gems/ruby-ip-0.9.1/lib/ip/socket.rb
tried also require 'ip'
and
require '../ip'
still same error
Backgroun info:
I installled ruby-ip so that I could invoke a method like: ip = IP.new do ...
gem installed ruby-ip
I can see the library ( I believe it's the ip.rb what I need to use;
pwd
/usr/lib/ruby/gems/1.8/gems/ruby-ip-0.9.1/lib
ls
ip ip.rb
environment info
ruby -v
ruby 1.8.7 (2012-10-12 patchlevel 371) [i386-linux]
gem list
*** LOCAL GEMS ***
builder (3.2.0)
eventmachine (1.0.1, 0.12.10)
pg (0.14.1, 0.13.2)
ruby-ip (0.9.1)
rubygems-update (2.0.0)
sqlite3 (1.3.3)
which ruby
/usr/bin/ruby
which gem
/usr/bin/gem
gem environment
RubyGems Environment:
- RUBYGEMS VERSION: 2.0.0
- RUBY VERSION: 1.8.7 (2012-10-12 patchlevel 371) [i386-linux]
- INSTALLATION DIRECTORY: /usr/lib/ruby/gems/1.8
- RUBY EXECUTABLE: /usr/bin/ruby
- EXECUTABLE DIRECTORY: /usr/bin
- RUBYGEMS PLATFORMS:
- ruby
- x86-linux
- GEM PATHS:
- /usr/lib/ruby/gems/1.8
- /home/pilar/.gem/ruby/1.8
- GEM CONFIGURATION:
- :update_sources => true
- :verbose => true
- :backtrace => false
- :bulk_threshold => 1000
- REMOTE SOURCES:
- http://rubygems.org/

Answer 1

Are you including require 'rubygems' too? It is necessary if you are using rvm.
Example:
[fotanus#thing ~]$ gem install ip
Fetching: ip-0.3.0.gem (100%)
Successfully installed ip-0.3.0
1 gem installed
Installing ri documentation for ip-0.3.0...
Installing RDoc documentation for ip-0.3.0...
[fotanus#thing ~]$ irb
1.8.7 :001 > require 'ip'
LoadError: no such file to load -- ip
from (irb):1:in `require'
from (irb):1
1.8.7 :002 > require 'rubygems'
=> true
1.8.7 :003 > require 'ip'
=> true
1.8.7 :004 >