I know that I can dump the entire information from a PEM certificate file with this command:

openssl x509 -in certfile -noout -text

And I've already found another direct parameter to show me only the expiry date of a certificate:

openssl x509 -in certfile -noout -enddate

But is there also a shortcut to get only the alternative names? Like when a certificate can be used for example.com as well as www.example.com. In the full dump, it's here:

Certificate:
    Data:
        X509v3 extensions:
            X509v3 Subject Alternative Name: 
                DNS:www.example.com, DNS:example.com

I'd just like to save me the hassle to parse this output and get the domain names only. Is that possible? Otherwise, what would be best practices to parse this output? What can be assumed, what may change? Could I use a regexp like X509v3 Subject Alternative Name:\s*DNS:(\S+)(?:, DNS:(\S+))*?