printbill - fair printing billing and accounting system.

printbill

printbill is a print filter, print-billing daemon, and associated administrative utilities which allow for accurate user-pays printing on Linux (and possibly other Unix/Unixish systems) based on toner consumption and page count. printbill(1) is the print filter, which parses command-line options given to it by lprng (with some extra ones specified in the as=... line in /etc/printcap). This does nothing but check and send the command-line options to printbilld, via a Unix-domain socket, which can then do one of several things depending on the --type argument given to printbill(1).

In all cases, a copy is made of a print job when it arrives at the front of the queue. In the case of --type accounting and --type lazybill, the server immediately returns JSUCC or JREMOVE (as appropriate - lazybill returns JREMOVE if the user has a quota less than or equal to zero) to the printbill(1) filter, then calculates the cost / page count / toner consumption afterwards. If --type is "bill", printbilld only allows the job to be printed after the billing process is complete and it is known whether or not the user can afford to print. When this occurs, the user is debited the cost of the print job and the job is printed via a secondary (non-user-accessable) print queue (the primary queue should use /dev/null as the printer device). This avoids the head-of-line problem, where user A prints 100 MB PS file, user B has to wait an hour to print a 3-page LaTeX document, by allowing jobs to be billed concurrently. The secondary print queue uses printbill_printer(1) as the print filter (achk=true is still required) - this only accepts jobs from the username under which printbilld and lprng are running.

Your choice of --type bill or --type lazybill depends on how long your users are prepared to wait for printing to start, and whether you allow people to go into debt (maybe insist on a substantial refundable deposit prior to printing!).

You can also specify --type quote, which just calculates the cost and e-mails/sends a winpopup message to the user who send the print job. See printbill(1) for details.

The actual billing process involves taking each postscript file, if necessary pre-processing with the optional anything-to-postscript converter, then processing it with GhostScript to standardise its format (as Windows drivers use several different techniques for specifying multiple copies). Next, it calculates the total number of copies of each page which are to be printed, and extracts a modified postscript file which contains just one copy of each page. This is then processed once again with Ghostscript, to produce a set of PNG images (one for each page) which are processed using percentblack(1) , percentcolour(1) or percent_cmy(1) programs (depending on the type of printer, which may either be a default printer or one explicitly described in printbillrc (5)). If billing is to be performed, the price of the total number of copies of all pages is calculated (paper costs plus toner/ink), and deducted from the users quota. Paper and ink/toner consumption is logged on a per-user and per-printer basis. If --type is "bill" and the user cannot afford the cost, or if the job was rejected for some other reason, the user is e-mailed with a brief yet vaguely informative message.

The configuration file printbillrc(5) includes a parameter limiting the maximum number of concurrent billing processes. If desired, this may be limited to one or two concurrent processes - two will be sufficient to deal with the head-of-line problems for small systems, although more shouldn't cause a problem. The pool of available processes is shared amongst all printqueues, so even if multiple printers are managed through a single server, the total number of processes remains limited. If all process slots are filled, pending jobs from different queues have an equal likelyhood of getting access to the next available process slot.

The current version of printbill supports multiple printers, with per-printer charge rates. Databases storing information about pages printed (global, per printer and per user), toner/ink (black and colour) consumption (per printer), quota levels per user, money paid in (global and per user), money actually spent (global and per user) are maintained by printbill and the related utilities.

printbilld(1) optionally writes detailed statistical information to a stats file unique to each printer. Each line of this stats file consists of the following information related to each file processed (not the cumulative total of all the files in a job):

timestamp

Time in seconds since the Epoch, as returned by time(2), when we started to process this job;

user time

User-space time spent by the printfilter in processing the job (typically very small);

system time

Operating system time spent by the printfilter in processing the job (typically even smaller than user time);

child user time

User-space time spent by child processes (ghostscript and percentcolour/black/cmy) - typically the bulk of processing time;

child system time

Operating system time spent by child processes (ghostscript and percentcolour/black/cmy);

file size

Size of the current file in bytes;

page count

Number of pages in this file;

cyan

Total percentage coverage of cyan ink/toner - zero for mono printers;

magenta

Total percentage coverage of magenta ink/toner - zero for mono printers;

yellow

Total percentage coverage of yellow ink/toner - zero for mono printers;

black

Total percentage coverage of black ink/toner - zero for CMY 3-colour printers.

printbill requires GhostScript (any version which can generate PNG images) and libpng2. The latter is a requirement of percentblack/percentcolour/percent_cmy, without which this program is essentially useless. It is strongly recommended that you install an anything-to-PostScript converter to allow things like plain text to be printed (e.g. from text editors!)

Please see the accompanying README file for detailed installation instructions. Chances are if you're reading this it's correctly installed. Note that the program and the accompanying utilities are written in Perl and so may be customised by the user very easily.

printbill and the accompanying utilities were written by Daniel Franklin (d.franklin@ieee.org). The web interface was written by Phil Ciufo (phil@snrc.uow.edu.au).

You can always grab the latest and greatest version from http://ieee.uow.edu.au/~daniel/software/printbill

/etc/printbill/printbillrc

This is fairly complex, and is now documented on its own manual page (see printbillrc(5)).

/etc/printbill/printers/*

Printer-specific overrides to printbillrc (see printbillrc(5) - these files use exactly the same format).

/etc/printbill/mail_message

This contains the message mailed to anybody who has a print job rejected. The default message just informs the user why their job may have been rejected, and suggests some possible remedies.

/var/lib/printbill/users/*.db

Current user quotas.

/var/lib/printbill/misc.db

Global page count, money paid and money spent are stored here.

/var/lib/printbill/printers/*.db

Printer databases - contain toner/ink usage and total pages printed.

/etc/printcap

To do pre-printing billing, you need to have printcap entries which look similar to this:

lp|Laser printer (scheduler queue - print to this)
 :lp=/dev/null
 :achk=true
 :as=|/usr/sbin/printbill --type bill --printbill_secondary real
 :sd=/var/spool/lpd/lp
 :mx#0
 :sh

real|Laser printer (real queue - you can't print to this) :lp=/dev/lp0 :achk=true :as=|/usr/sbin/printbill_printer :if=.... (if you need an input filter, e.g. PS -> PCL) :sd=/var/spool/lpd/lp_real :mx#0 :sh

If you want --type "lazybill", "account" or "quote", you don't specify a --printbill_secondary (or define the 'real' queue) - for the "quote" type you should use lp=/dev/null.

You may add an additional print-filter, in case you don't have a PostScript printer. Obviously, if the scripts are located somewhere else, adjust your printcap and config files accordingly.

printbill(1) printbilld(1) printbill_configure(8), printbill_grapher(1), percentblack(1), percentcolour(1), percent_cmy(1), pqcheck(1), printquote(1), printbill_printer(1), printbillrc(5), printcap(5), init_from_passwd(8), pqm(8).