I searched the Internet in vain for examples of using the Ruby i18n gem outside of Rails apps.

Below is a minimal example: the aim is (as usual) to produce a greeting - this time in English and Italian.

Installation

$ irb
>> require 'rubygems'
=> true
>> require 'sun_times'
=> true
>> SunTimes.set( Date.today, 44, 11 ).localtime
=> Tue Mar 09 18:14:08 +0100 2010

The t method

The most common use of i18n is via I18n.translate which has an abbreviated alias I18n.t.

Translations

en.yml:

en:
  hello world: Hello World!

it.yml:

it:
  hello world: Ciao Mondo!

These translations can be accessed as follows:

I18n.t('hello world')

That will use the current locale setting. You can change it as follows:

I18n.locale = :it

The Program

After loading the i18n gem, set up I18n.load_path before attempting to retrieve any translations.

require 'rubygems' if RUBY_VERSION < '1.9'
require 'i18n'

I18n.load_path = ['en.yml', 'it.yml']

puts 'In English...'
I18n.locale = :en
puts I18n.t('hello world')

puts 'In Italian...'
I18n.locale = :it
puts I18n.t('hello world')

The result:

$ ruby salutation.rb
In English...
Hello World!
In Italian...
Ciao Mondo!