title: How can I test if line is empty in shell script?
body: <p>I have a shell script like this: </p>
  
  <pre><code>cat file | while read line
  do
      # run some commands using $line    
  done
  </code></pre>
  
  <p>Now I need to check if the line contains any non-whitespace character ([\n\t ]), and if not, skip it.
  How can I do this?</p>