title: shell script purpose of x in "x$VARIABLE"
body: <p>I'm peeking through some shell scripts - what's the purpose of the x in the comarison shcu as</p>
  
  <pre><code> if [ "x$USER" != "x$RUN_AS_USER" ]; then
          su - $RUN_AS_USER -c "$CATALINA_HOME/bin/startup.sh"
   else
          $CATALINA_HOME/bin/startup.sh
   fi
  </code></pre>