<?php

if ($argc != 2) {
    exit(1);
}

$files = array(
    'debian' => '/etc/debian_version',
    'fedora' => '/etc/fedora-release',
    'redhat' => '/etc/redhat-release'
);

if (!array_key_exists($argv[1], $files)) {
    exit(1);
}

if ($argv[1] === 'freebsd') {
    echo getFreebsdVersion();
    exit(0);
}

$func = $argv[1] === 'debian' ? 'getDebianVersion' : 'getRedhatVersion';
$func($files[$argv[1]]);

function getFreebsdVersion()
{
    preg_match("/^FreeBSD ([0-9]+\.*[0-9]*).+$/i", shell_exec('uname -v'), $matches);
    return isset($matches[1]) ? (int) $matches[1] : 0;
}

function getRedhatVersion($file)
{
    preg_match("/[a-zA-Z]+ release ([0-9].*) .+/", @file_get_contents($file), $matches);
    return isset($matches[1]) ? (int) $matches[1] : 0;
}

function getDebianVersion($file)
{
    $v = @file_get_contents($file);
    return $v === false ? 0 : $v;
}