Control macOS startup chime

setchime.sh

#!/usr/bin/env bash
set -eu -o pipefail

## based on work by Mr. Macintosh: https://mrmacintosh.com/how-to-enable-the-mac-startup-chime-on-your-2016-macbook-pro/
## hattip DaringFireball: https://daringfireball.net/linked/2020/02/25/mac-startup-chime

##========================================================================
## To the extent possible under law, Darren Meyer has waived all copyright 
## and related or neighboring rights to setchime.sh
##========================================================================

on='%00'
off='%01'

setting=$(nvram StartupMute|cut -f 2)

case "$setting" in
	$on)
		setting="on"
		;;
	$off)
		setting="off"
		;;
esac

echo "Startup Chime is currently $setting"
if [ "$setting" == "${1:-}" ]
then
	echo "No change needed"
	exit 0
fi

case "${1:-''}" in
	on)
		sudo nvram StartupMute=${on}
		echo "Startup Chime is now enabled"
		;;
	off)
		sudo nvram StartupMute=${off}
		echo "Startup Chime is now disabled"
		;;
	*)
		;;
esac