Answers for "how to get value in log file magento2"

logger magento2

$writer = new \Zend\Log\Writer\Stream(BP . '/var/log/test.log');
$logger = new \Zend\Log\Logger();
$logger->addWriter($writer);
$logger->info('Your text message');

mage log equivalent magento 2

\Magento\Framework\App\ObjectManager::getInstance()->get(\Psr\Log\LoggerInterface::class)->debug('Your message here');