/etc/pm/sleep.d/00lock-screen

00lock-screen

#!/bin/sh
# Lock screen

lock_screen()
{
    XLOCK="i3lock -c 000000"

    if [ -e /proc/acpi/battery ]; then
        XLOCK="${XLOCK} -d"
    fi

    for x in /tmp/.X11-unix/*; do
        displaynum=`echo $x | sed s#/tmp/.X11-unix/X##`
        user=`who | grep -m1 "(:$displaynum)" | awk '{print $1}'`
        if [ x"$user" = x"" ]; then
            user=`who | grep -m1 ":$displaynum" | awk '{print $1}'`
        fi
        if [ x"$user" != x"" ]; then
            export DISPLAY=":$displaynum"
            /bin/su -c "$XLOCK" "$user"
            return 0
        fi
    done
}

case "$1" in
    hibernate|suspend)
        lock_screen
        ;;
esac