title: Shell scripting illegal number error
body: <p>I was checking whether a file exists or not but i get error with the following code</p>
  
  <pre><code>filename="a.txt"
  if [ -s $filename ] ; then  
      echo "exists"
  else
      echo "not exists"
  fi
  </code></pre>
  
  <p>It gives the error [: 116: Illegal number</p>
  
  <p>What could be the problem?</p>