pg_ctl(1)'s -w option works well if the default user can automatically authenticate without any user intervention. The attached patch checks the error message to see if it's asking for a password. The theory being that if it's asking for a password, the backend is up. I'm not entirely happy with the fact that I'm dependent on the error message text, but I couldn't easily figure out a better way to test this via libpq(3), so I'm not too unhappy... it's just not elegant.
psql and pg_dump test for this same error string, so you're in good
company on that front, but password prompting is not the only or even
the most likely misleading failure. I believe both the Red Hat and
Debian distributions set the default auth method to IDENT, meaning that
the message you'd likely get is going to be a bleat about IDENT auth
failing, not a password request. Unfortunately that message is going to
be localized, but it should have a SQLSTATE assigned, so you could
check for ERRCODE_INVALID_AUTHORIZATION_SPECIFICATION ...
Ok, I've read over the code a little bit... it doesn't seem like there's an obvious way to get the error code via libpq(3). CopyErrorData() looks promising, but I'm running out of time to find a better way to do this. Were you hinting at extending libpq(3) to having the backend send the errcode to the frontend? -sc
-- Sean Chittenden
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