title: How to execute ssh-keygen without prompt
body: <p>I want to automate generate a pair of ssh key using shell script on Centos7, and I have tried</p>
  
  <pre><code>yes "y" | ssh-keygen -t rsa
  echo "\n\n\n" | ssh-keygen...
  echo | ssh-keygen..
  </code></pre>
  
  <p>all of these command doesn't work, just input one 'enter' and the shell script stopped on "Enter passphrase (empty for no passphrase)",
  I just want to know how to simulate mutiple 'enter' in shell continuously.</p>
  
  <p>Many thanks if anyone can help !</p>