Remove old kernel versions, by keeping only the active one and the latest one

remove-old-kernel-versions.php

#!/usr/bin/php
<?php
try {
	$doEcho = true;
	$action = 'view';
	if(isset($argv) && is_array($argv) && (count($argv) == 2)) {
		$action = strtolower($argv[1]);
		switch($action) {
			case 'view':
			case 'simulate':
			case 'batch':
				break;
			case 'get-command':
				$doEcho = false;
				break;
			case 'h':
			case '-h':
			case 'help':
			case '--help':
				echo "{$argv[0]} [view|simulate|get-command|batch]\n";
				die(0);
			default:
				throw new Exception("Unknown option: $action\nSyntax:\n{$argv[0]} [view|simulate|get-command|batch]");
		}
	}

	$rxVersion = '(\\d[\\d\\-\\.]+\\d)(-[a-z][a-z0-9]*)?';

	$currentVersion = launch('uname -r 2>&1');
	if(!preg_match('/^' . $rxVersion . '$/i', $currentVersion)) {
		throw new Exception("Currently active kernel version not recognized: $currentVersion");
	}
	if($doEcho) {
		echo "Current version   : $currentVersion\n";
	}

	$installedVersions = array();
	$files = @scandir('/boot');
	if((!is_array($files)) || empty($files)) {
		throw new Exception("Unable to retrieve the contents of the /boot folder");
	}
	$prefixes = array('System.map-', 'config-', 'initrd.img-', 'vmlinuz-');

	foreach($files as $file) {
		if(!is_file("/boot/$file")) {
			continue;
		}
		$ok = false;
		foreach($prefixes as $p) {
			if(strpos($file, $p) === 0) {
				$v = substr($file, strlen($p));
				if(!preg_match('/^' . $rxVersion . '$/i', $v)) {
					throw new Exception("Installed active kernel version not recognized: $v (file: $file)");
				}
				if(!in_array($v, $installedVersions, true)) {
					$installedVersions[] = $v;
				}
				break;
			}
		}
	}
	if(empty($installedVersions)) {
		throw new Exception('No installed kernel versions found');
	}
	usort($installedVersions, 'version_compare');
	if($doEcho) {
		echo "Installed versions: ", implode(', ', $installedVersions), "\n";
	}

	if(!in_array($currentVersion, $installedVersions, true)) {
		throw new Exception('The current version is not in the installed versions found');
	}

	$latestVersion = $installedVersions[count($installedVersions) - 1];
	if($doEcho) {
		echo "Latest version    : $latestVersion\n";
	}

	$versionsToRemove = array();
	foreach($installedVersions as $installedVersion) {
		switch($installedVersion) {
			case $currentVersion:
			case $latestVersion:
				break;
			default:
				$versionsToRemove[] = $installedVersion;
				break;
		}
	}
	if($doEcho) {
		echo "Versions to remove: ", empty($versionsToRemove) ? 'none' :implode(', ', $versionsToRemove) , "\n";
	}
	if(($action === 'view') || empty($versionsToRemove)) {
		return;
	}
	$cmd = 'remove --purge ';
	foreach($versionsToRemove as $versionToRemove) {
		foreach(array('linux-headers-', 'linux-image-') as $prefix) {
			if(preg_match('/(\\d[\\d\\-\\.]+\\d)-[a-z]+[a-z][0-9]*$/', $versionToRemove, $match)) {
				$cmd .= " $prefix{$match[1]} $prefix{$match[1]}-*";
			}
			else {
				$cmd .= " $prefix$versionToRemove";
			}
		}
	}
	switch($action) {
		case 'simulate':
			$cmd = "apt-get --simulate $cmd";
			$rc = null;
			system($cmd, $rc);
			if($rc !== 0) {
				throw new Exception("Command failed:\n$cmd");
			}
			break;
		case 'get-command':
			$cmd = "apt-get $cmd";
			echo $cmd, "\n";
			break;
		case 'batch':
			$cmd = "apt-get --quiet --assume-yes --force-yes $cmd";
			echo "Executing command:\n$cmd\n";
			system($cmd, $rc);
			if($rc !== 0) {
				throw new Exception("Command failed!");
			}
			break;
	}
	die(0);
}
catch(Exception $x) {
	$msg = trim($x->getMessage()) . "\n";
	$hStdErr = @fopen('php://stderr', 'w');
	if($hStdErr === false) {
		echo $msg;
	}
	else {
		fwrite($hStdErr, $msg);
		fclose($hStdErr);
	}
	$rc = $x->getCode();
	die($rc ? $rc : 1);
}

function launch($command) {
	$output = array();
	$rc = null;
	@exec($command, $output, $rc);
	$output = is_array($output) ? implode("\n", $output) : '';
	if($rc !== 0) {
		throw new Exception("Command failed with return code $rc:\n$command" . (strlen($output) ? "\n$output" : ''));
	}
	return $output;
}