[cups-devel] Temporary print queues

[Till Kamppeter]

On 05/17/2017 10:47 PM, Michael Sweet wrote:
> Since the most recent changes in the Github sources, the "lp" and "lpr" programs will auto-create queues,

Tried with "lp" and it did not do so. I have used the destination name 
as reported by cupsEnumDests(). Now cupsd, libcups.so.2, lp, lpoptions, 
and lpstat are from GIT. cups-browsed is not running.

> however the "lpstat" program is specifically written to report the status of print queues.
>

OK.

> We *could* add an lpstat option to enumerate discovered printers (please file a bug...) but I wouldn't want to change "lpstat -p" or "lpstat -v" to list discovered (but not configured) queues as that might cause compatibility issues.
>

OK, but it would be great by having a way to run cupsEnumDests() from 
the command line. An extra flag to supply to the call of lpstat would be 
great.

> No, in the current implementation cupsd only discards temporary queues on exit, so generally speaking they will go away several seconds after the last job completes.
>

Would work well on systems where CUPS terminates a few minutes after 
finishing all jobs. If CUPS is held up because there is a shared queue 
or a stuck job, the temporary queues would stay until system shutdown or 
removal of the stuck job. Perhaps a timeout for temporary queue removal 
would be more adequate.

>> 3. If I start cupsd and then call cupsEnumDests() I get a list of available printers, including the DNS-SD-discovered ones. Now I call an API function to make CUPS create a temporary queue for a DNS-SD-discovered printer. This makes the auto-generated PPD file appear in /etc/cups/ppd/. Now I stop cupsd and the PPD is still there. Should it not disappear as the temporary queue disappears when CUPS terminates?
>
> It should delete the PPD - please file a bug.
>

OK, will do.

>> I use Ubuntu Zesty with CUPS 2.2.2 but have replaced libcups.so.2 by the current GIT state of the art of CUPS (and restarted cupsd, cups-browsed, and avahi-daemon).
>
> It would be useful if you could test things with all of the current Github code...

I have seen that the recent (code, not documentation) changes are only 
on the cups/ and scheduler/ directories, not for example on systemv/. 
Now I have also updated the scheduler, lp, lpstat, and lpoptions.

    Till