title: How to add line with spaces at beginning, and with backslash at end with sed?
body: <p>I know the sed syntax to add a line after another line in a file, which is</p>
  
  <pre><code>sed -i '/LINE1/a LINE2' FILE
  </code></pre>
  
  <p>This adds LINE2 after LINE1 in FILE correct? How do I add a line with a backslash at the end? For example, from</p>
  
  <pre><code>This is a a line \
      Indented line1 \
      Indented line2 \
      Line3
  </code></pre>
  
  <p>To</p>
  
  <pre><code>This is a a line \
      Indented line1 \
      Indented line2 \
      Added line \
      Line3
  </code></pre>