title: Shell scripting removing negative integer
body: <p>How can we remove negative sign from a integer in shell?</p>
  
  <p>Say <code>diff=-234</code>; how can we make <code>diff=234</code>?</p>
  
  <p>I tried with</p>
  
  <pre><code>if [ $diff -lt 0 ]
  then
      diff=$(expr $diff \* -1)
  fi
  </code></pre>
  
  <p>but this is not working.</p>