title: installing hpricot
body: <p>I'm trying to install <code>hpricot</code> and am getting the following error. I do have xcode installed but I'm not sure what else I'm missing.</p>
  
  <pre><code>$ gem install hpricot
  Building native extensions.  This could take a while...
  ERROR:  Error installing hpricot:
      ERROR: Failed to build gem native extension.
  
          /Users/user_name/.rvm/rubies/ruby-1.9.3-p194/bin/ruby extconf.rb
  checking for stdio.h... *** extconf.rb failed ***
  Could not create Makefile due to some reason, probably lack of
  necessary libraries and/or headers.  Check the mkmf.log file for more
  details.  You may need configuration options.
  </code></pre>
  
  <p>I also tried nokogiri.</p>
  
  <pre><code>$ gem install nokogiri
  Building native extensions.  This could take a while...
  ERROR:  Error installing nokogiri:
      ERROR: Failed to build gem native extension.
  
          /Users/user_name/.rvm/rubies/ruby-1.9.3-p194/bin/ruby extconf.rb
  checking for libxml/parser.h... *** extconf.rb failed ***
  Could not create Makefile due to some reason, probably lack of
  necessary libraries and/or headers.  Check the mkmf.log file for more
  details.  You may need configuration options.
  </code></pre>