Using multiple subkeys in GPG

[Andreas John]

Hi!

I have read the "Using multiple subkeys in GPG"-Article =
(http://fortytwo.ch/gpg/subkeys/) and tried it just out of curiosity.

Although I don't want to use this "trick", but I believe someone out =
there might and I want my program to be prepared...

My question is: How can I tell that a secret primary-key is really =
present and not just unusable when invoking GPG with "<primary-keyid>!".
I mean how to tell programmatically.=20

The article mentions=20
    gpg --export-secret-keys | gpg --list-packets
where "primary secret key should be marked with 'gnu-dummy S2K'."

Is this the only way? Shouldn't the "sc"-Flags be missing in the =
"--list-secret-keys --with-colons" too?


Bye!