printing-advanced.html

FreeBSD操作系统的详细使用手册

<p>However, an output filter is <span class="emphasis"><i
class="EMPHASIS">necessary</i></span> if you want header pages and need to send escape
sequences or other initialization strings to be able to print the header page. (But it is
also <span class="emphasis"><i class="EMPHASIS">futile</i></span> if you want to charge
header pages to the requesting user's account, since <b class="APPLICATION">LPD</b> does
not give any user or host information to the output filter.)</p>

<p>On a single printer, <b class="APPLICATION">LPD</b> allows both an output filter and
text or other filters. In such cases, <b class="APPLICATION">LPD</b> will start the
output filter to print the header page (see section <a
href="printing-advanced.html#PRINTING-ADVANCED-HEADER-PAGES">Header Pages</a>) only. <b
class="APPLICATION">LPD</b> then expects the output filter to <span class="emphasis"><i
class="EMPHASIS">stop itself</i></span> by sending two bytes to the filter: ASCII 031
followed by ASCII 001. When an output filter sees these two bytes (031, 001), it should
stop by sending <var class="LITERAL">SIGSTOP</var> to itself. When <b
class="APPLICATION">LPD</b>'s done running other filters, it will restart the output
filter by sending <var class="LITERAL">SIGCONT</var> to it.</p>

<p>If there is an output filter but <span class="emphasis"><i
class="EMPHASIS">no</i></span> text filter and <b class="APPLICATION">LPD</b> is working
on a plain text job, <b class="APPLICATION">LPD</b> uses the output filter to do the job.
As stated before, the output filter will print each file of the job in sequence with no
intervening form feeds or other paper advancement, and this is probably <span
class="emphasis"><i class="EMPHASIS">not</i></span> what you want. In almost all cases,
you need a text filter.</p>

<p>The program <tt class="COMMAND">lpf</tt>, which we introduced earlier as a text
filter, can also run as an output filter. If you need a quick-and-dirty output filter but
do not want to write the byte detection and signal sending code, try <tt
class="COMMAND">lpf</tt>. You can also wrap <tt class="COMMAND">lpf</tt> in a shell
script to handle any initialization codes the printer might require.</p>
</div>

<div class="SECT3">
<h3 class="SECT3"><a id="PRINTING-ADVANCED-LPF" name="PRINTING-ADVANCED-LPF">9.4.1.6 <tt
class="COMMAND">lpf</tt>: a Text Filter</a></h3>

<p>The program <tt class="FILENAME">/usr/libexec/lpr/lpf</tt> that comes with FreeBSD
binary distribution is a text filter (input filter) that can indent output (job submitted
with <tt class="COMMAND">lpr -i</tt>), allow literal characters to pass (job submitted
with <tt class="COMMAND">lpr -l</tt>), adjust the printing position for backspaces and
tabs in the job, and account for pages printed. It can also act like an output
filter.</p>

<p><tt class="COMMAND">lpf</tt> is suitable for many printing environments. And although
it has no capability to send initialization sequences to a printer, it is easy to write a
shell script to do the needed initialization and then execute <tt
class="COMMAND">lpf</tt>.</p>

<p>In order for <tt class="COMMAND">lpf</tt> to do page accounting correctly, it needs
correct values filled in for the <var class="LITERAL">pw</var> and <var
class="LITERAL">pl</var> capabilities in the <tt class="FILENAME">/etc/printcap</tt>
file. It uses these values to determine how much text can fit on a page and how many
pages were in a user's job. For more information on printer accounting, see <a
href="printing-advanced.html#PRINTING-ADVANCED-ACCT">Accounting for Printer
Usage</a>.</p>
</div>
</div>

<div class="SECT2">
<h2 class="SECT2"><a id="PRINTING-ADVANCED-HEADER-PAGES"
name="PRINTING-ADVANCED-HEADER-PAGES">9.4.2 Header Pages</a></h2>

<p>If you have <span class="emphasis"><i class="EMPHASIS">lots</i></span> of users, all
of them using various printers, then you probably want to consider <span
class="emphasis"><i class="EMPHASIS">header pages</i></span> as a necessary evil.</p>

<p>Header pages, also known as <span class="emphasis"><i
class="EMPHASIS">banner</i></span> or <span class="emphasis"><i class="EMPHASIS">burst
pages</i></span> 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.)</p>

<p>The <b class="APPLICATION">LPD</b> system can provide header pages automatically for
your printouts <span class="emphasis"><i class="EMPHASIS">if</i></span> your printer can
directly print plain text. If you have a <span class="TRADEMARK">PostScript</span>
printer, you will need an external program to generate the header page; see <a
href="printing-advanced.html#PRINTING-ADVANCED-HEADER-PAGES-PS">Header Pages on <span
class="TRADEMARK">PostScript</span> Printers</a>.</p>

<div class="SECT3">
<h3 class="SECT3"><a id="PRINTING-ADVANCED-HEADER-PAGES-ENABLING"
name="PRINTING-ADVANCED-HEADER-PAGES-ENABLING">9.4.2.1 Enabling Header Pages</a></h3>

<p>In the <a href="printing-intro-setup.html#PRINTING-SIMPLE">Simple Printer Setup</a>
section, we turned off header pages by specifying <var class="LITERAL">sh</var> (meaning
``suppress header'') in the <tt class="FILENAME">/etc/printcap</tt> file. To enable
header pages for a printer, just remove the <var class="LITERAL">sh</var> capability.</p>

<p>Sounds too easy, right?</p>

<p>You are right. You <span class="emphasis"><i class="EMPHASIS">might</i></span> 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:</p>

<pre class="PROGRAMLISTING">
#!/bin/sh
#
#  hpof - Output filter for Hewlett Packard PCL-compatible printers
#  Installed in /usr/local/libexec/hpof

printf "\033&amp;k2G" || exit 2
exec /usr/libexec/lpr/lpf
</pre>

<p>Specify the path to the output filter in the <var class="LITERAL">of</var> capability.
See the <a href="printing-advanced.html#PRINTING-ADVANCED-OF">Output Filters</a> section
for more information.</p>

<p>Here is an example <tt class="FILENAME">/etc/printcap</tt> file for the printer <var
class="LITERAL">teak</var> that we introduced earlier; we enabled header pages and added
the above output filter:</p>

<pre class="PROGRAMLISTING">
#
#  /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:
</pre>

<p>Now, when users print jobs to <var class="LITERAL">teak</var>, they get a header page
with each job. If users want to spend time searching for their printouts, they can
suppress header pages by submitting the job with <tt class="COMMAND">lpr -h</tt>; see the
<a href="printing-using.html#PRINTING-LPR-OPTIONS-MISC">Header Page Options</a> section
for more <a href="http://www.FreeBSD.org/cgi/man.cgi?query=lpr&sektion=1"><span
class="CITEREFENTRY"><span class="REFENTRYTITLE">lpr</span>(1)</span></a> options.</p>

<div class="NOTE">
<blockquote class="NOTE">
<p><b>Note:</b> <b class="APPLICATION">LPD</b> 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 <var class="LITERAL">ff</var> capability in <tt
class="FILENAME">/etc/printcap</tt>.</p>
</blockquote>
</div>
</div>

<div class="SECT3">
<h3 class="SECT3"><a id="PRINTING-ADVANCED-HEADER-PAGES-CONTROLLING"
name="PRINTING-ADVANCED-HEADER-PAGES-CONTROLLING">9.4.2.2 Controlling Header
Pages</a></h3>

<p>By enabling header pages, <b class="APPLICATION">LPD</b> will produce a <span
class="emphasis"><i class="EMPHASIS">long header</i></span>, a full page of large letters
identifying the user, host, and job. Here is an example (kelly printed the job named
outline from host <tt class="HOSTID">rose</tt>):</p>

<pre class="PROGRAMLISTING">
      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
</pre>

<p><b class="APPLICATION">LPD</b> appends a form feed after this text so the job starts
on a new page (unless you have <var class="LITERAL">sf</var> (suppress form feeds) in the
destination printer's entry in <tt class="FILENAME">/etc/printcap</tt>).</p>

<p>If you prefer, <b class="APPLICATION">LPD</b> can make a <span class="emphasis"><i
class="EMPHASIS">short header</i></span>; specify <var class="LITERAL">sb</var> (short
banner) in the <tt class="FILENAME">/etc/printcap</tt> file. The header page will look
like this:</p>

<pre class="PROGRAMLISTING">
rose:kelly  Job: outline  Date: Sun Sep 17 11:07:51 1995
</pre>

<p>Also by default, <b class="APPLICATION">LPD</b> prints the header page first, then the
job. To reverse that, specify <var class="LITERAL">hl</var> (header last) in <tt
class="FILENAME">/etc/printcap</tt>.</p>
</div>

<div class="SECT3">
<h3 class="SECT3"><a id="PRINTING-ADVANCED-HEADER-PAGES-ACCOUNTING"
name="PRINTING-ADVANCED-HEADER-PAGES-ACCOUNTING">9.4.2.3 Accounting for Header
Pages</a></h3>

<p>Using <b class="APPLICATION">LPD</b>'s built-in header pages enforces a particular
paradigm when it comes to printer accounting: header pages must be <span
class="emphasis"><i class="EMPHASIS">free of charge</i></span>.</p>

<p>Why?</p>

<p>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 <span
class="emphasis"><i class="EMPHASIS">user or host</i></span> 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 <tt class="COMMAND">lpr
-h</tt>. They could still be charged for header pages they did not print. Basically, <tt
class="COMMAND">lpr -h</tt> will be the preferred option of environmentally-minded users,
but you cannot offer any incentive to use it.</p>

<p>It is <span class="emphasis"><i class="EMPHASIS">still not enough</i></span> 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 <tt
class="COMMAND">lpr -h</tt>, they will still get them and be charged for them since <b
class="APPLICATION">LPD</b> does not pass any knowledge of the <var
class="OPTION">-h</var> option to any of the filters.</p>

<p>So, what are your options?</p>

<p>You can:</p>

<ul>
<li>
<p>Accept <b class="APPLICATION">LPD</b>'s paradigm and make header pages free.</p>
</li>

<li>
<p>Install an alternative to <b class="APPLICATION">LPD</b>, such as <b
class="APPLICATION">LPRng</b>. Section <a
href="printing-lpd-alternatives.html">Alternatives to the Standard Spooler</a> tells more
about other spooling software you can substitute for <b class="APPLICATION">LPD</b>.</p>
</li>

<li>
<p>Write a <span class="emphasis"><i class="EMPHASIS">smart</i></span> 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 <b class="APPLICATION">LPD</b> will start the output filter only for the
header pages. And the output filter can parse the header page text that <b
class="APPLICATION">LPD</b> 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 <var
class="LITERAL">af</var> 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 <var
class="LITERAL">sh</var> (short header) capability in <tt
class="FILENAME">/etc/printcap</tt>. Then again, all that might be too much trouble, and
users will certainly appreciate the more generous system administrator who makes header
pages free.</p>
</li>
</ul>
</div>

<div class="SECT3">
<h3 class="SECT3"><a id="PRINTING-ADVANCED-HEADER-PAGES-PS"
name="PRINTING-ADVANCED-HEADER-PAGES-PS">9.4.2.4 Header Pages on <span
class="TRADEMARK">PostScript</span> Printers</a></h3>

<p>As described above, <b class="APPLICATION">LPD</b> can generate a plain text header
page suitable for many printers. Of course, <span class="TRADEMARK">PostScript</span>
cannot directly print plain text, so the header page feature of <b
class="APPLICATION">LPD</b> is useless--or mostly so.</p>

<p>One obvious way to get header pages is to have every conversion filter and the text
filter generate the header page. The filters 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 <tt class="COMMAND">lpr -h</tt>.</p>

<p>Let us explore this method. The following script takes three arguments (user login
name, host name, and job name) and makes a simple <span
class="TRADEMARK">PostScript</span> header page:</p>

<pre class="PROGRAMLISTING">
#!/bin/sh
#
#  make-ps-header - make a PostScript header page on stdout
#  Installed in /usr/local/libexec/make-ps-header
#

#