title: execute printf command shell script
body: <p>I am a beginner in writing shell script (probably my 1st shell script).
  I have a shell script that I like to run. The command is a simple grep command based on the parameter passed to it. I managed to get the correct grep command using the script below. </p>
  
  <pre><code>FILE='testurls'
  MERCHANT_ID='8'
  printf "grep '^%s' %s\n" "$MERCHANT_ID" "$FILE"
  
  ./hello.sh 
  grep '^8' testurls
  </code></pre>
  
  <p>How would I execute the command instead of printing it.</p>