#!/bin/sh
help() {
cat <<EOF
$0 [-d <display_name>] [-x <x>] [-y <y>] [-ref <rate>]
'xrandr' with no arguments will give you a listing.
EOF
printf 'Defaults: x: %-6d y: %-6d ref: %-6.2f\n' "$x" "$y" "$ref"
exit 1
}
display=DisplayPort-0 
x=3840 
y=2160 
ref=110.00 
while [ $# -gt 0 ] ; do case $1 in
    -d) display="$2" ; shift ; shift ;;
    -x) x="$2"; shift ; shift ;;
    -y) y="$2"; shift ; shift ;;
    -ref) ref="$(printf "%0.2f" "$2")"; shift ; shift ;;
    *) help;;
esac ; done
modename="${x}x${y}_$ref"
mdline="$(cvt "$x" "$y" "$ref" | sed -ne's/^Modeline "[^"]*"//p')" 
#shellcheck disable=SC2086
xrandr --newmode "$modename" $mdline 
xrandr --addmode "$display" "$modename" 
xrandr --output "$display" --mode "$modename"