title: R Sys.getenv() returns the wrong value
body: <p>I am using R in ubuntu. The environment variable value returned is wrong. I had the environment variable set to a value. After a disk crash, I changed its value. However the R will always return the old value. I don't know where R cached the old value and insists on returning the old value.</p>
  
  <h2>The environment variable's new value</h2>
  
  <pre><code>echo $WFDATA
  /current/environment/value
  </code></pre>
  
  <h2>Start a new R terminal</h2>
  
  <pre><code>R
  &gt; Sys.getenv('WFDATA')
  [1] "/old/environment/value"
  </code></pre>
  
  <h2>Now try to set the environment variable to the new value</h2>
  
  <pre><code>&gt; Sys.setenv(WFDATA='/current/environment/value')
  &gt; Sys.getenv('WFDATA')
  [1] "/current/environment/value"
  &gt; q()
  Save workspace image? [y/n/c]: y
  </code></pre>
  
  <h2>Start a new R terminal and you still get the old value</h2>
  
  <pre><code>&gt; Sys.getenv('WFDATA')
  [1] "/old/environment/value"
  &gt; 
  </code></pre>
  
  <p>Not sure why R is so stubborn as to remember the old value. Any one can suggest a way to fix this problem? This problem appears in both the R session and in the Rscript file.</p>