Keeping $DISPLAY up-to-date

• $DISPLAY can change with X forwarding when connecting from different hosts

• Old shells in detached screens don't know where you're connecting from

• If not in screen, dump variables to ~/.display. If in screen, read ~/.display:

• Test for $WINDOW to determine if screen is running or not

    if test -z "$WINDOW"
    then export | egrep -- '-x (DISPLAY|XAUTHORITY)=' > ~/.display
    else test -r ~/.display && source ~/.display
    fi