title: If I want to create a file every 12 hours, how can I compare it with the old one with bash
body: <p>I want to monitor new subdomains with bash, so I want to scan subdomains every 12 hours automatically with <strong>cron</strong>.
  Then compare the new text file with the old one to see if there is any difference. if I make the script output every time with <code>&quot;$(date '+sube_%I:%M-%p_%d_%m_%Y')&quot;</code> How can I compare it with the old one with bash?</p>