title: Multi threading in command line possible?
body: <p>I'm using the following command to check the whois information from a list of domains in a text file and then output any lines that contain an email to a new file:</p>
  
  <pre><code>for i in $(cat testdomains.txt); do whois $i| egrep [a-zA-Z0-9]@[a-zA-Z0-9]\.[a-zA-Z0-9]; done &gt;&gt; results.txt
  </code></pre>
  
  <p>Is there any way to speed this up by checking more than one domain at a time?  For example, right now it is going from one domain to the next checking the information. Is there anything I could change in the command to make it check 50 domains at a time?</p>