detect_external_monitor.sh

#!/bin/bash

# origin:
# https://bbs.archlinux.org/viewtopic.php?id=171655
#inspired of: 
#   http://unix.stackexchange.com/questions/4489/a-tool-for-automatically-applying-randr-configuration-when-external-display-is-p
#   http://ozlabs.org/~jk/docs/mergefb/
#   http://superuser.com/questions/181517/how-to-execute-a-command-whenever-a-file-changes/181543#181543

# arandr script
# xrandr --output HDMI2 --off --output HDMI1 --mode 1920x1080 --pos 1920x0 --rotate normal --output DP1 --off --output eDP1 --mode 1920x1080 --pos 0x0 --rotate normal --output VIRTUAL1 --off
export MONITOR2=/sys/class/drm/card0-HDMI-A-1/status

while inotifywait -e modify,create,delete,open,close,close_write,access $MONITOR2;

dmode="$(cat $MONITOR2)"

do
    if [ "${dmode}" = disconnected ]; then
         /usr/bin/xrandr --auto
         echo "${dmode}"
    elif [ "${dmode}" = connected ];then
         /usr/bin/xrandr --output eDP1 --mode 1920x1080 --pos 0x0 --output HDMI1 --mode 1920x1080 --pos 1920x0
         echo "${dmode}"
    else /usr/bin/xrandr --auto
         echo "${dmode}"
    fi
done