[freetds] dblib question - handling bad login name/password from auser

Lowden, James K LowdenJK at bernstein.com
Mon Apr 26 13:23:36 EDT 2004


> From: Andy Cranston [mailto:a.cranston at selwaymoore.com]
> Sent: April 26, 2004 11:59 AM
> 
> However I'd like to write my own handlers.  The main reason 
> being to catch
> an invalid login attempt via:
> 
>   dbproc = dbopen(login, DEFAULT_SERVER);
> 
> Instead of the program bombing out I'd like to be able to gracefully
> reprompt for another username and password.
> 
> Am I right in thinking I need to amend the handler routines 
> to do this?  If
> so any suggestions on a "clean" way to do this.  

Andy, 

You might want to check simply that you got a non-null dbproc.  There are several possible causes for not being able to log in (user error being only the most common with a working setup).   Passing the message to the user (using your handler) will at least provide the information to the person who needs it, whether or not it's understood. ;-)

The simplest way in general to pass information from the handler to the main code is through a global variable.  In a threaded environment, that translates to thread local storage or a per-thread map.  When you call a db-lib function that causes the library or the server to emit a message or error, you are assured that your handler will be invoked before the function returns.  The sequence is always

	call dbsomething
	[a bad thing happens]
	handler invoked
	dbsomething returns

IOW, you never have to worry about a race condition.  Or, at any rate, behavior in exception to my description would be considered a bug.  I don't believe I've seen that written down anywhere, but I can't think of any exceptions.  

--jkl

-----------------------------------------
The information contained in this transmission may contain privileged and confidential information and is intended only for the use of the person(s) named above. If you are not the intended recipient, or an employee or agent responsible for delivering this message to the intended recipient, any review, dissemination, distribution or duplication of this communication is strictly prohibited. If you are not the intended recipient, please contact the sender immediately by reply e-mail and destroy all copies of the original message. Please note that we do not accept account orders and/or instructions by e-mail, and therefore will not be responsible for carrying out such orders and/or instructions.
If you, as the intended recipient of this message, the purpose of which is to inform and update our clients, prospects and consultants of developments relating to our services and products, would not like to receive further e-mail correspondence from the sender, please "reply" to the sender indicating your wishes.  In the U.S.: 1345 Avenue of the Americas, New York, NY 10105.





More information about the FreeTDS mailing list