title: replace all '/' with '\/' in bash/shell script
body: <p>This might be very simple but I am stuck at getting this done in shell/bash.
  I have input like "<code>a/b/c/d</code>" and I want to replace all '<code>/</code>' with '<code>\/</code>' and the output would be 'a/b/c/d'</p>
  
  <p>another example is <code>12.12.12.12/32</code>  >>> <code>12.12.12.12\/32</code></p>
  
  <p>Any help would be appreciated.</p>