main-disk-free.php

<?php

$home = rtrim(getenv('HOME'), '\\/');

$moreDirs = array_slice($_SERVER['argv'], 1);

$output = `df -h`;
if (!preg_match('#(\d+)% +/\s#', "$output ", $match)) {
	echo trim($output) . "\n";
	exit(1);
}

$curWhen = date('Y-m-d');
$curMainPct = (int) $match[1];
$curMores = array_map(function($dir) {
	$output = `du -s $dir`;
	$bytes = (int) trim($output);
	return ceil($bytes / 1024);
}, $moreDirs);

if (file_exists($file = "$home/.main-disk-free")) {
	$history = json_decode(trim(file_get_contents($file)), true) ?: [];
	$history = array_map(fn($el) => (array) $el, $history);

	$prevWhen = max(array_keys($history));
	$prevMainPct = $history[$prevWhen][0];
	$prevMores = array_slice($history[$prevWhen], 1);
}
else {
	$prevWhen = '-';
	$prevMainPct = 0;
	$prevMores = [];
}

$notify = $curMainPct != $prevMainPct;
if ($notify || $curMores != $prevMores) {
	$history[$curWhen] = [$curMainPct, ...$curMores];
	file_put_contents($file, json_encode($history) . "\n");

	if ($notify) {
		echo "$curMainPct%\n";
		if ($prevMainPct) {
			echo "\n";
			echo "$prevMainPct% ($prevWhen)\n";
		}
	}
}