title: Determining the type of terminal (classic Unix terminal vs graphical terminal)
body: <p>I'm configuring my prompt (<code>PS1</code>) via <strong>.bashrc</strong> and found one issue with my current configuration: I am using a 256 color scheme. This is not compatible with the classical terminal (accessible via e.g. <kbd>Ctrl</kbd>+<kbd>Alt</kbd>+<kbd>F2</kbd>) but looks beautiful in graphical terminals such as gnome-terminal, terminator, etc.</p>
  
  <p>So I have to change my prompt depending on the type of terminal. To do this, I need a condition for <code>if</code> clause to test the type of terminal. Do you know how to do this?</p>