function lx11 () # List X11 DISPLAY. { local x=( /tmp/.X11-unix/X* ) [ -e "$x" ] && echo "${x[@]/*\/X/:}" } function chx11 () #= [DISPLAY] # CHange X11 DISPLAY. { local x=( $(lx11) ) (( 0 < ${#x[@]} || 0 < $# )) && DISPLAY="${1:-$x}" } # Set DISPLAY if X11 is runnning. [ -z "$DISPLAY" ] && chx11