selection-only

// per with only: the default selection is "only these elements". Of all the systemd services of a Linux,
// sshd and cron are watched by default; the administrator adds others on the probe, by name or by pattern.
need('protocol:ssh');

per('service', 'Services', array('only' => array('sshd', 'cron')));
output('state', 'text', array('label' => 'State', 'per' => 'service'));

watch.expect('stopped', 'Service not running', 'state', array('critical' => array('active')));

// One line per service, "cron.service loaded active running Regular background program processing daemon".
$units = ssh.run('systemctl list-units --type=service --all --plain --no-legend');
foreach (text.lines($units['output']) as $line) {
    $m = text.match($line, '([^ ]+)\.service +[^ ]+ +([^ ]+)');
    if (list.count($m) > 0) {
        value('state', $m[2], $m[1]);
    }
}