7.6.2. Header Pages

If you have lots of users, all of them using various printers, then you probably want to consider header pages as a necessary evil.

Header pages, also known as banner or burst pages identify to whom jobs belong after they are printed. They are usually printed in large, bold letters, perhaps with decorative borders, so that in a stack of printouts they stand out from the real documents that comprise users' jobs. They enable users to locate their jobs quickly. The obvious drawback to a header page is that it is yet one more sheet that has to be printed for every job, their ephemeral usefulness lasting not more than a few minutes, ultimately finding themselves in a recycling bin or rubbish heap. (Note that header pages go with each job, not each file in a job, so the paper waste might not be that bad.)

The LPD system can provide header pages automatically for your printouts if your printer can directly print plain text. If you have a PostScript printer, you will need an external program to generate the header page; see Header Pages on PostScript Printers.

7.6.2.1. Enabling Header Pages

In the Simple Printer Setup, we turned off header pages by specifying sh (meaning ``suppress header'') in the /etc/printcap file. To enable header pages for a printer, just remove the sh capability.

Sounds too easy, right?

You are right. You might have to provide an output filter to send initialization strings to the printer. Here is an example output filter for Hewlett Packard PCL-compatible printers:

#!/bin/sh
#
#  hpof - Output filter for Hewlett Packard PCL-compatible printers
#  Installed in /usr/local/libexec/hpof


printf "\033&k2G" || exit 2
exec /usr/libexec/lpr/lpf

Here is an example /etc/printcap file for the printer teak that we introduced earlier; we enabled header pages and added the above output filter:

#
#  /etc/printcap for host orchid
#
teak|hp|laserjet|Hewlett Packard LaserJet 3Si:\
	:lp=/dev/lpt0:sd=/var/spool/lpd/teak:mx#0:\
	:if=/usr/local/libexec/hpif:\
	:vf=/usr/local/libexec/hpvf:\
	:of=/usr/local/libexec/hpof:

Note: LPD prints a form feed character after the header page. If your printer uses a different character or sequence of characters to eject a page, specify them with the ff capability in /etc/printcap.

7.6.2.2. Controlling Header Pages

By enabling header pages, LPD will produce a long header, a full page of large letters identifying the user, host, and job. Here is an example (kelly printed the job named outline from host rose):

k                   ll       ll
k                    l        l
k                    l        l
k   k     eeee       l        l     y    y
k  k     e    e      l        l     y    y
k k      eeeeee      l        l     y    y
kk k     e           l        l     y    y
k   k    e    e      l        l     y   yy
k    k    eeee      lll      lll     yyy y
                                         y
                                    y    y
                                     yyyy


                             ll
                    t         l        i
                    t         l
 oooo    u    u   ttttt       l       ii     n nnn     eeee
o    o   u    u     t         l        i     nn   n   e    e
o    o   u    u     t         l        i     n    n   eeeeee
o    o   u    u     t         l        i     n    n   e
o    o   u   uu     t  t      l        i     n    n   e    e
 oooo     uuu u      tt      lll      iii    n    n    eeee









r rrr     oooo     ssss     eeee
rr   r   o    o   s    s   e    e
r        o    o    ss      eeeeee
r        o    o      ss    e
r        o    o   s    s   e    e
r         oooo     ssss     eeee







					Job:  outline
					Date: Sun Sep 17 11:04:58 1995

If you prefer, LPD can make a short header; specify sb (short banner) in the /etc/printcap file. The header page will look like this:

rose:kelly  Job: outline  Date: Sun Sep 17 11:07:51 1995

7.6.2.3. Accounting for Header Pages

Using LPD's built-in header pages enforces a particular paradigm when it comes to printer accounting: header pages must be free of charge.

Why?

Because the output filter is the only external program that will have control when the header page is printed that could do accounting, and it is not provided with any user or host information or an accounting file, so it has no idea whom to charge for printer use. It is also not enough to just ``add one page'' to the text filter or any of the conversion filters (which do have user and host information) since users can suppress header pages with lpr -h. They could still be charged for header pages they did not print. Basically, lpr -h will be the preferred option of environmentally-minded users, but you cannot offer any incentive to use it.

It is still not enough to have each of the filters generate their own header pages (thereby being able to charge for them). If users wanted the option of suppressing the header pages with lpr -h, they will still get them and be charged for them since LPD does not pass any knowledge of the -h option to any of the filters.

So, what are your options?

You can

• Accept LPD's paradigm and make header pages free.
• Install an alternative to LPD, such as LPDng or PLP. Section Alternatives to the Standard Spooler tells more about other spooling software you can substitute for LPD.
• Write a smart output filter. Normally, an output filter is not meant to do anything more than initialize a printer or do some simple character conversion. It is suited for header pages and plain text jobs (when there is no text (input) filter). But, if there is a text filter for the plain text jobs, then LPD will start the output filter only for the header pages. And the output filter can parse the header page text that LPD generates to determine what user and host to charge for the header page. The only other problem with this method is that the output filter still does not know what accounting file to use (it is not passed the name of the file from the af capability), but if you have a well-known accounting file, you can hard-code that into the output filter. To facilitate the parsing step, use the sh (short header) capability in /etc/printcap. Then again, all that might be too much trouble, and users will certainly appreciate the more generous system administrator who makes header pages free.

7.6.2.4. Header Pages on PostScript Printers

As described above, LPD can generate a plain text header page suitable for many printers. Of course, PostScript cannot directly print plain text, so the header page feature of LPD is useless---or mostly so.

One obvious way to get header pages is to have every conversion filter and the text filter generate the header page. The filters should should use the user and host arguments to generate a suitable header page. The drawback of this method is that users will always get a header page, even if they submit jobs with lpr -h.

Let us explore this method. The following script takes three arguments (user login name, host name, and job name) and makes a simple PostScript header page:

#!/bin/sh
#
#  make-ps-header - make a PostScript header page on stdout
#  Installed in /usr/local/libexec/make-ps-header
#

#
#  These are PostScript units (72 to the inch).  Modify for A4 or
#  whatever size paper you are using:
#
page_width=612
page_height=792
border=72

#
#  Check arguments
#
if [ $# -ne 3 ]; then
    echo "Usage: `basename $0` <user> <host> <job>" 1>&2
    exit 1
fi

#
#  Save these, mostly for readability in the PostScript, below.
#
user=$1
host=$2
job=$3
date=`date`

#
#  Send the PostScript code to stdout.
#
exec cat <<EOF
%!PS

%
%  Make sure we do not interfere with user's job that will follow
%
save

%
%  Make a thick, unpleasant border around the edge of the paper.
%
$border $border moveto
$page_width $border 2 mul sub 0 rlineto
0 $page_height $border 2 mul sub rlineto
currentscreen 3 -1 roll pop 100 3 1 roll setscreen
$border 2 mul $page_width sub 0 rlineto closepath
0.8 setgray 10 setlinewidth stroke 0 setgray

%
%  Display user's login name, nice and large and prominent
%
/Helvetica-Bold findfont 64 scalefont setfont
$page_width ($user) stringwidth pop sub 2 div $page_height 200 sub moveto
($user) show

%
%  Now show the boring particulars
%
/Helvetica findfont 14 scalefont setfont
/y 200 def
[ (Job:) (Host:) (Date:) ] {
	200 y moveto show /y y 18 sub def
} forall

/Helvetica-Bold findfont 14 scalefont setfont
/y 200 def
[ ($job) ($host) ($date) ] {
	270 y moveto show /y y 18 sub def
} forall

%
%  That is it
%
restore
showpage
EOF

#!/bin/sh
#
#  psdf - DVI to PostScript printer filter
#  Installed in /usr/local/libexec/psdf
#
#  Invoked by lpd when user runs lpr -d
#

orig_args="$@"

fail() {
    echo "$@" 1>&2
    exit 2
}

while getopts "x:y:n:h:" option; do
    case $option in
        x|y)  ;; # Ignore
	n)    login=$OPTARG ;;
	h)    host=$OPTARG ;; 
	*)    echo "LPD started `basename $0` wrong." 1>&2
              exit 2
              ;;
    esac
done

[ "$login" ] || fail "No login name"
[ "$host" ] || fail "No host name"

( /usr/local/libexec/make-ps-header $login $host "DVI File"
  /usr/local/bin/dvips -f ) | eval /usr/local/libexec/lprps $orig_args

As we have mentioned before, the above scheme, though fairly simple, disables the ``suppress header page'' option (the -h option) to lpr. If users wanted to save a tree (or a few pennies, if you charge for header pages), they would not be able to do so, since every filter's going to print a header page with every job.

To allow users to shut off header pages on a per-job basis, you will need to use the trick introduced in section Accounting for Header Pages: write an output filter that parses the LPD-generated header page and produces a PostScript version. If the user submits the job with lpr -h, then LPD will not generate a header page, and neither will your output filter. Otherwise, your output filter will read the text from LPD and send the appropriate header page PostScript code to the printer.

If you have a PostScript printer on a serial line, you can make use of lprps, which comes with an output filter, psof, which does the above. Note that psof does not charge for header pages.