title: How do I determine if my R installation on OS X has the "--enable-R-shlib" option enabled?
body: <p>I've installed R on my OS X machine via the .pkg method. I'm trying to get a Ruby gem called RSRuby to work and though it installed correctly, it's throwing an error when I try to invoke the gem. </p>
  
  <pre><code>Fatal error: R home directory is not defined
  </code></pre>
  
  <p>The RSRuby documentation states that R should be installed with the option --enable-R-shlib. But the R documentation states that the Mac OS X installation does this by default. How can you verify that this option is enabled on an installation if you don't know it was explicitly called during installation?</p>
  
  <p>I'm chasing down why RSRuby can't find R home directory and this seems like the most likely problem. </p>
  
  <p>Per RSRuby documentation, I copied this into my home directory</p>
  
  <pre><code>[~]$ R_HOME=/Library/Frameworks/R.framework/Resource
  </code></pre>
  
  <p>And from the R console, this is the output:</p>
  
  <pre><code>&gt; R.home()
  [1] "/Library/Frameworks/R.framework/Resources"
  </code></pre>
  
  <p>And during gem install, I ran this command:</p>
  
  <pre><code>gem install rsruby -- --with-R-dir=$R_HOME=/Library/Frameworks/R.framework/Resources
  </code></pre>
  
  <p>Also, these are the contents of my /Library/Frameworks/R.framework/Libraries folder:</p>
  
  <pre><code>[Libraries]$ ls
  i386                    libRblas.dylib.dSYM     libgfortran.2.dylib
  libR.dylib              libRblas.vecLib.dylib   libreadline.5.2.dylib
  libR.dylib.dSYM         libRlapack.dylib        libreadline.dylib
  libRblas.0.dylib        libRlapack.dylib.dSYM   ppc
  libRblas.dylib          libgcc_s.1.dylib        x86_64
  </code></pre>