void+sndio volume controller and manager script

vman.pl

#!/usr/bin/perl

# i wouldn't recommend using this in its current state. because it uses sndioctl instead
# of using libsndio directly, there's pretty much no way to detect server restarts &c.
# this will be rewritten as a small C program soon.

# this is intended to be run as a per-user service
# https://docs.voidlinux.org/config/services/user-services.html

use strict;
use warnings;

use IO::Socket::UNIX;
use File::Slurper qw(read_text write_text);

my $vol;

sub detect_output {
	# this is extremely platform dependent. figure out how to muck with /proc/asound for your machine
	open(my $codec, "<", "/proc/asound/PCH/codec#0");
	my $hit = 0;
	while (<$codec>) {
		/Node 0x1b/ and $hit = 1;
		if ($hit && /Pin-ctls/) {
			$vol = /OUT/ ? "./vol_spkr" : "./vol_hp";
			last;
		}
	}
	close $codec;
}

sub run_cmd {
	my $cmd = shift;
	my $out = `sndioctl $cmd`;
	$? and die "sndiod is down";
	write_text $vol, $out;
}

sub restore_vol {
	my $cmd = read_text($vol);
	run_cmd $cmd;
}

detect_output;
restore_vol;

my $acpi = IO::Socket::UNIX->new(
	Type => SOCK_STREAM(),
	Peer => "/run/acpid.socket"
);

while (<$acpi>) {
	chomp;
	my @event = split;
	if    ($event[0] eq "button/volumedown") { run_cmd "output.level=-0.05"; }
	elsif ($event[0] eq "button/volumeup")   { run_cmd "output.level=+0.05"; }
	elsif ($event[0] eq "jack/headphone") {
		if    ($event[2] eq "unplug") { $vol = "./vol_spkr"; }
		elsif ($event[2] eq "plug")   { $vol = "./vol_hp"; }
		restore_vol;
	}
	# TODO: implement simulated mute, run detect_output on wakeup, visual feedback, etc.
}

vol_hp

output.level=0.3

vol_spkr

output.level=0.6