How do I run a user-installed Ruby gem as a different user? -

I set a hook because it runs fine as one of my regular users, under that user Install the necessary gems using gem install - user-installed . Now I want to run the hook as a separate user, but when I try, Ruby can not find the gems set up:

  $ /home/user/.gem /ruby/1.9. 1 / bin / jekyll /usr/lib/ruby/1.9.1/rubygems/dependency.rb7247:in `to_specs': jacail (& gt; = 0) could not be found [rack-1.5.2, rack-protection-1.5 .0, Ruby-Opinid-2.8.8, Pappara-1.0, Tilting -1.3.6] (Gem :: Load Errors) /usr/lib/ruby/1.9.1/rubygems/dependency.rb:256:in- To / srpc '/usr/lib/ruby/1.9.1/rubygems.rb: 1210: in / emo / user / .gem / ruby ​​/ 1.9.1 / bin / jekyll18: in` & lt; From `gem 'main & gt; '   
 
 
 You should know Ruby where its gems are installed Environment  GEM_HOME  controls this, so you can do something like this:  
  Export GEM_HOME = / home / user / .gem / ruby ​​/ 1.9.1 $ GEM_HOME / bin / Jquile help