printing to a remote IPP printer with lp is dang hard

[Andrew Pimlott]

This is a repost of Debian bug 429715[1] on cupsys-client, which has
thus-far gone unanswered.

My friend gave me the IPP URL of his printer.  Not knowing much about
this newfangled protocol, I installed cupsys-client, thinking (based on
the package description) it would be a cinch to use the printer.  (This
Debian package contains the lp* family of commands.)  It turned out to
be an ordeal.  I'd like feedback on what I did wrong, or how this could
be made easier and less frustrating.

The URL was of the form

    ipp://192.168.0.10/printers/HPLJ1012

I started by looking in the lp and lpstat man pages, expecting to find a
URL option.  Nothing.  Then I tried to find some documentation on what
to do with the URL, what parts of it to pass to what options of
lp/lpstat.  All I found was the IPP URL RFC, which isn't very accessible
and is not helpful directly.

So I experimented.  I started with the lpstat program.  Passing
192.168.0.10 to the -h option was fairly obvious.  Using the -r option,
I was able to ping the server.  But using, say, -t returned several
repetitions of "lpstat: Forbidden" and nothing else useful.  I figured
maybe I had to query this printer specifically.  The first problem is I
didn't know whether the name of the printer should be
"/printers/HPLJ1012", "HPLJ1012", or something else.  I tried passing
variations to -a, -p, and -v, but I always got "lpstat: Unknown
destination \"HPLJ1012\"!".  So it seemed like the remote server didn't
recognize the printer name.  But when I investigated further by running
the command under strace, I found that the string HPLJ1012 was never
even sent to the server!  In fact, the "Unknown destination" message was
printed after failed attempts to read a file called lpoptions.  Why it
needs to read a local file about a remote printer I have no idea.  I
looked at the lpoptions man page, but I didn't see anything that looked
relevant.

At a loss, I turned my attention to lp, and finally I caught a break.  I
passed HPLJ1012 to the -d option, gave a PDF file on the command line
(although the man page says nothing about what format the file should be
in, so that was a guess), and got a printout.  Looking at the strace of
the run, I found it curious that there were several "POST /" requests
that all got "403 Forbidden" responses, before finally a "POST
/printers/HPLJ1012" (hey--this program does know how to construct the
URL, it just doesn't accept it!) succeeded.  I don't know whether this
represents a misconfiguration of the server (which is running CUPS), or
futility on the part of the client.  And even after this, I never
figured out how to use lpstat to get job status, etc.

So in the end, I can at least print (though not query), but I still
don't know how I was supposed to figure it out.  If I missed something,
maybe it could be documented more prominently.

Andrew

[1] http://bugs.debian.org/429715

-- 
I've decided to go back to school.  Kindergarden.