title: Bash sed function not working on Mac OS X
body: <p>Can anyone tell me how to change this command:</p>
  
  <pre><code>sed -i.bak "/group :test/ a gem 'selenium-webdriver'" Gemfile 
  </code></pre>
  
  <p>To work on Mac?
  Getting this error:</p>
  
  <pre><code>sed: 1: "/group :test/ a gem 'se ...": command a expects \ followed by text
  </code></pre>
  
  <p>I was trying to do a\ but didn't help.</p>