title: Why is $DISPLAY sometimes :0 and sometimes :1
body: <p>I'm using xmacro to record keyboard shortcuts, which requires a <code>$DISPLAY</code> to replay on. But, sometimes my <code>$DISPLAY</code> is <strong>:0</strong> and sometimes <strong>:1</strong>, so every time that happens I have to change the value manually. Why does it keep changing, and is there a way to set the <code>$DISPLAY</code> value to either <strong>:0</strong> or <strong>:1</strong> permanently? (I can export <code>DISPLAY=:0</code> in one terminal, but that doesn't change the value of <code>$DISPLAY</code> in new terminals.)</p>