title: How to determine whether a given Linux is 32 bit or 64 bit?
body: <p>When I type <code>uname -a</code>, it gives the following output.</p>
  
  <pre><code>Linux mars 2.6.9-67.0.15.ELsmp #1 SMP Tue Apr 22 13:50:33 EDT 2008 i686 i686 i386 GNU/Linux
  </code></pre>
  
  <p>How can I know from this that the given OS is 32 or 64 bit?</p>
  
  <p>This is useful when writing <code>configure</code> scripts, for example: what architecture am I building for?</p>