things for msweet to add to his (next) book

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In article <1716-cups.development at news.easysw.com>,
 Michael Sweet <mike at easysw.com> wrote:

> What kinds of examples are you looking for?

The nature of the *cupsFilter key (mentioned in a related thread) had me 
pounding my head on my desk for a good three hours. The book doesn't 
discuss the topic much and the error_log isn't any help since CUPS is 
working correctly (i.e., the route it chose ... through the initial 
filter only ... was technically correct). A discussion of what filter to 
bind via *cupsFilter and why would be a useful investment in the book 
(I've penned in notes to mine).

The other items that tripped me up were how to create routes in the 
first place. Until one groks the singular nature of .convs entries 
creating chains can prove distracting. Your response to another fellow 
having similar "how do I create chains" type of query gave me the "a 
ha!" info I needed to put that piece of the puzzle in place. To be 
truthful the very nature of filters and the costing piece in .conv 
implies that chaining is standard behavior. The only missing piece is 
"how?"

The default thought that came to my brain when the notion of filter 
chaining arose was the desire to simply specify A-Z routes in some file 
somewhere as a single record. Write/work the description from that basis 
and I think you'll connect with more people.

The only other piece of the puzzle that left me wanting was the question 
you just answered. Namely, what errors can a filter return that will 
block progression but not shut down the queue. Further what does CUPS do 
with errors returned by a filter.

My first installation/test was a filter that crashed almost immediately. 
*That* did shut off the print queue. That particular queue config looked 
like this:

queue -> lone filter -> ... -> /dev/null

I'd also like to see an option in lpadmin to *read* the current config 
of a given printer. Like this...

lpadmin -p foo --status

....or something along those lines. With a result along the lines of:

Printer: foo
<summary of the current state of all the lpadmin settable switches>

Best,
JR