title: Triangular background for bash PS1 prompt
body: <p>I am trying to get a triangular background for bash PS1 prompt.
  <a href="https://i.stack.imgur.com/g9rGk.png" rel="noreferrer"><img src="https://i.stack.imgur.com/g9rGk.png" alt="as shown here"></a></p>
  
  <p>I have tried the existing library called <code>powerline</code> but it seems to be heavy for my ageing laptop. I have managed to get the background colour, but have no idea of getting the shape. Currently what I have is:
  <a href="https://i.stack.imgur.com/x3LSA.png" rel="noreferrer"><img src="https://i.stack.imgur.com/x3LSA.png" alt="my PS1"></a>.</p>
  
  <p>Is there any straight-forward way of having those shape?</p>
  
  <p>I am using:</p>
  
  <pre><code>$ echo $TERM
  xterm-256color
  $ echo $SHELL
  /bin/bash
  $ bash --version
  GNU bash, version 4.3.42(1)-release (x86_64-redhat-linux-gnu)
  </code></pre>