title: RVM: specify a ruby version to use
body: <p>I know how to use RVM, but now I have a weird problem, which I do not understand why.</p>
  
  <p>Here is the simple story (I am using Ubuntu):</p>
  
  <p>I have created a Rails project, the direcotry of this project is "bookstore/".</p>
  
  <p>I go to project directory by <code>cd bookstore</code> , and type command <code>rvm list</code> like following:</p>
  
  <pre><code>bookstore/$ rvm list
  
  rvm rubies
  
     ruby-1.9.2-p136 [ i386 ]
     ruby-1.8.7-p352 [ i386 ]
     ruby-1.8.7-p330 [ i386 ]
     ruby-1.8.6-p420 [ i386 ]
     ruby-1.9.2-p290 [ i386 ]
  </code></pre>
  
  <p>Since I did not see the <code>=&gt;</code> arrow sign which is supposed to indicate the current ruby version in use, so I specify the ruby version with the following <strong>RVM</strong> command:</p>
  
  <pre><code>bookstore/$ rvm use ruby-1.9.2-p290
  Using /home/usr/.rvm/gems/ruby-1.9.2-p290
  </code></pre>
  
  <p>Now, if I <code>rvm list</code> I see my project is using <strong>ruby v1.9.2</strong> :</p>
  
  <pre><code>bookstore/$ rvm list
  rvm rubies
  
     ruby-1.9.2-p136 [ i386 ]
     ruby-1.8.7-p352 [ i386 ]
     ruby-1.8.7-p330 [ i386 ]
     ruby-1.8.6-p420 [ i386 ]
  =&gt; ruby-1.9.2-p290 [ i386 ]
  </code></pre>
  
  <p><strong>Every thing works fine at this point!</strong></p>
  
  <p><strong>But</strong>, if now I <strong>open a new terminal window</strong> on Ubuntu, and <code>cd</code> to the project directory, and run the command <code>rvm list</code> again, I got:</p>
  
  <pre><code>bookstore/$ rvm list
  
  rvm rubies
  
      ruby-1.9.2-p136 [ i386 ]
      ruby-1.8.7-p352 [ i386 ]
      ruby-1.8.7-p330 [ i386 ]
      ruby-1.8.6-p420 [ i386 ]
      ruby-1.9.2-p290 [ i386 ]
  </code></pre>
  
  <p>Where is the <code>=&gt;</code> to indicate the ruby version I specified previously? <strong>Why it again needs me to specify the ruby version?</strong> </p>
  
  <p>It happens always when I <strong>open a new terminal window</strong>. How to have my project "remember" the ruby version I have specified? </p>