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<!-- This is an SGML document in the linuxdoc DTD describing
     Printing with FreeBSD.  By Sean Kelly, 1995.

     $Id: printing.sgml,v 1.21 1997-10-11 11:20:20 jraynard Exp $

     The FreeBSD Documentation Project

<!DOCTYPE linuxdoc PUBLIC "-//FreeBSD//DTD linuxdoc//EN">

  <article>
      <title> Printing with FreeBSD
      <author> Sean Kelly <tt/kelly@fsl.noaa.gov/
      <date> 30 September 1995, (c) 1995

      <abstract> This document describes printing with FreeBSD.  It
	tells how to set up printer hardware, how to configure FreeBSD
	to use printers, and how to control the print queue and print
	a variety of file formats. </abstract>

    <toc>
-->

  <chapt><heading>Printing<label id="printing"></heading>

    <p><em>Contributed by &a.kelly;<newline>30 September 1995</em>

        In order to use printers with FreeBSD, you will need to set
	them up to work with the Berkeley line printer spooling
	system, also known as the LPD spooling system.  It is the
	standard printer control system in FreeBSD.  This section
	introduces the LPD spooling system, often simply called LPD.

	If you are already familiar with LPD or another printer
	spooling system, you may wish to skip to section <ref
	id="printing:intro:setup" name="Setting up the spooling
	system">.

      <sect><heading>What the Spooler Does<label
	    id="printing:intro:spooler"></heading>

	<p> LPD controls everything about a host's printers.  It is
	  responsible for a number of things:

	  <itemize>
	    <item>It controls access to attached printers and
	      printers attached to other hosts on the network.

	    <item>It enables users to submit files to be printed;
	      these submissions are known as <em/jobs/.

	    <item>It prevents multiple users from accessing a printer
	      at the same time by maintaining a <em/queue/ for each
	      printer.

	    <item>It can print <em/header pages/ (also known as
	      <em/banner/ or <em/burst/ pages) so users can easily
	      find jobs they have printed in a stack of printouts.

	    <item>It takes care of communications parameters for
	      printers connected on serial ports.

	    <item>It can send jobs over the network to another LPD
	      spooler on another host.

	    <item>It can run special filters to format jobs to be
	      printed for various printer languages or printer
	      capabilities.

	    <item>It can account for printer usage.
	  </itemize>

	  Through a configuration file, and by providing the special
	  filter programs, you can enable the LPD system to do all or
	  some subset of the above for a great variety of printer
	  hardware.

      <sect><heading>Why You Should Use the Spooler<label
	    id="printing:intro:why"></heading> 

	<p> If you are the sole user of your system, you may be
	  wondering why you should bother with the spooler when you
	  do not need access control, header pages, or printer
	  accounting.  While it is possible to enable direct access to
	  a printer, you should use the spooler anyway since

	  <itemize>
	    <item>LPD prints jobs in the background; you do not have
	      to wait for data to be copied to the printer.

	    <item>LPD can conveniently run a job to be printed
	      through filters to add date/time headers or convert a
	      special file format (such as a TeX DVI file) into a
	      format the printer will understand.   You will not have to do
	      these steps manually.

	    <item>Many free and commercial programs that provide a
	      print feature usually expect to talk to the spooler on
	      your system.  By setting up the spooling system, you will
	      more easily support other software you may later add or
	      already have.
	  </itemize>

      <sect><heading>Setting Up the Spooling System<label
	    id="printing:intro:setup"></heading>

	<p> To use printers with the LPD spooling system, you will need
	  to set up both your printer hardware and the LPD software.
	  This document describes two levels of setup:

	  <itemize>
	    <item>See section <ref name="Simple Printer Setup"
		id="printing:simple"> to learn how to connect a
		printer, tell LPD how to communicate with it, and
		print plain text files to the printer.

	    <item>See section <ref name="Advanced Printer Setup"
		id="printing:advanced"> to find out how to print a
		variety of special file formats, to print header
		pages, to print across a network, to control access to
		printers, and to do printer accounting.
	  </itemize>


    <sect><heading>Simple Printer Setup<label
	  id="printing:simple"></heading>

      <p> This section tells how to configure printer hardware and the
	LPD software to use the printer.  It teaches the basics:

	<itemize>
	  <item>Section <ref id="printing:hardware" name="Hardware
	    Setup"> gives some hints on connecting the printer to a
	    port on your computer.

	  <item>Section <ref id="printing:software" name="Software
	    Setup"> shows how to setup the LPD spooler configuration
	    file <tt>/etc/printcap</tt>.
	</itemize>

        If you are setting up a printer that uses a network protocol
	to accept data to print instead of a serial or parallel interface,
	see <ref id="printing:advanced:network:net-if" name="Printers
	  With Networked Data Stream Interaces">.

	Although this section is called ``Simple Printer Setup,'' it is
	actually fairly complex.  Getting the printer to work with
	your computer and the LPD spooler is the hardest part.  The
	advanced options like header pages and accounting are fairly
	easy once you get the printer working.

      <sect1><heading>Hardware Setup<label id="printing:hardware"></heading>

	<p> This section tells about the various ways you can connect a
	  printer to your PC.  It talks about the kinds of ports and
	  cables, and also the kernel configuration you may need to
	  enable FreeBSD to speak to the printer.

	  If you have already connected your printer and have
	  successfully printed with it under another operating system,
	  you can probably skip to section <ref id="printing:software"
	  name="Software Setup">.

	<sect2><heading>Ports and Cables<label
	      id="printing:ports"></heading> 

	  <p> Nearly all printers you can get for a PC today support
	    one or both of the following interfaces:

	    <itemize>
	      <item><em/Serial/ interfaces use a serial port on your
		computer to send data to the printer.  Serial
		interfaces are common in the computer industry and
		cables are readily available and also easy to
		construct.  Serial interfaces sometimes need special
		cables and might require you to configure somewhat
		complex communications options.

	      <item><em/Parallel/ interfaces use a parallel port on
		your computer to send data to the printer.  Parallel
		interfaces are common in the PC market.  Cables are
		readily available but more difficult to construct by
		hand.  There are usually no communications options
		with parallel interfaces, making their configuration
		exceedingly simple.

		<p> Parallel interfaces are sometimes known as
		  ``Centronics'' interfaces, named after the connector
		  type on the printer.
	    </itemize>

	    In general, serial interfaces are slower than parallel
	    interfaces.  Parallel interfaces usually offer just
	    one-way communication (computer to printer) while serial
	    gives you two-way.  Many newer parallel ports can also
	    receive data from the printer, but only few printers need
	    to send data back to the computer.  And FreeBSD does not
	    support two-way parallel communication yet.

	    Usually, the only time you need two-way communication with
	    the printer is if the printer speaks PostScript.
	    PostScript printers can be very verbose.  In fact,
	    PostScript jobs are actually programs sent to the printer;
	    they need not produce paper at all and may return results
	    directly to the computer.  PostScript also uses
	    two-way communication to tell the computer about problems,
	    such as errors in the PostScript program or paper jams.
	    Your users may be appreciative of such information.
	    Furthermore, the best way to do effective accounting with
	    a PostScript printer requires two-way communication: you
	    ask the printer for its page count (how many pages it has
	    printed in its lifetime), then send the user's job, then
	    ask again for its page count. Subtract the two values and
	    you know how much paper to charge the user.

	    So, which interface should you use?

	    <itemize>
	      <item>If you need two-way communication, use a serial
		port.  FreeBSD does not yet support two-way
		communication over a parallel port.

	      <item>If you do not need two-way communication and can
		pick parallel or serial, prefer the parallel
		interface.  It keeps a serial port free for other
		peripherals---such as a terminal or a modem---and is
		faster most of the time.  It is also easier to
		configure.

	      <item>Finally, use whatever works.	
	    </itemize>


	<sect2><heading>Parallel Ports<label id="printing:parallel"></heading>

	  <p> To hook up a printer using a parallel interface, connect
	    the Centronics cable between the printer and the
	    computer. The instructions that came with the printer, the
	    computer, or both should give you complete guidance.

	    Remember which parallel port you used on the computer. The
	    first parallel port is /dev/lpt0 to FreeBSD; the second is
	    /dev/lpt1, and so on.

	<sect2><heading>Serial Ports<label id="printing:serial"></heading>

	  <p> To hook up a printer using a serial interface, connect
	    the proper serial cable between the printer and the
	    computer.  The instructions that came with the printer,
	    the computer, or both should give you complete guidance.

	    If you are unsure what the ``proper serial cable'' is, you
	    may wish to try one of the following alternatives:
	    <itemize>
	      <item>A <em/modem/ cable connects each pin of the
		connector on one end of the cable straight through to
		its corresponding pin of the connector on the other
		end.  This type of cable is also known as a DTE-to-DCE
		cable.

	      <item>A <em/null-modem/ cable connects some pins
		straight through, swaps others (send data to receive
		data, for example), and shorts some internally in each
		connector hood.  This type of cable is also known as a
		DTE-to-DTE cable.

	      <item>A <em/serial printer/ cable, required for some
		unusual printers, is like the null modem cable, but
		sends some signals to their counterparts instead of
		being internally shorted.
	    </itemize>

	    You should also set up the communications parameters for
	    the printer, usually through front-panel controls or DIP
	    switches on the printer.  Choose the highest bps (bits per
	    second, sometimes <em/baud rate/) rate that both your
	    computer and the printer can support.  Choose 7 or 8 data
	    bits; none, even, or odd parity; and 1 or 2 stop bits.
	    Also choose a flow control protocol: either none, or
	    XON/XOFF (also known as <em/in-band/ or <em/software/)
	    flow control.  Remember these settings for the software
	    configuration that follows.

      <sect1><heading>Software Setup<label id="printing:software"></heading>

	<p> This section describes the software setup necessary to
	  print with the LPD spooling system in FreeBSD.

	  Here is an outline of the steps involved:
	  <enum>
	    <item>Configure your kernel, if necessary, for the port
	      you are using for the printer; section <ref
	      id="printing:kernel" name="Kernel Configuration"> tells
	      you what you need to do.

	    <item>Set the communications mode for the parallel port,
	      if you are using a parallel port; section <ref
	      id="printing:parallel-port-mode" name = "Setting the
	      Communication Mode for the Parallel Port"> gives
	      details.

	    <item>Test if the operating system can send data to the
	      printer.  Section <ref id="printing:testing"
	      name="Checking Printer Communications"> gives some
	      suggestions on how to do this.

	    <item>Set up LPD for the printer by modifying the file
	      <tt>/etc/printcap</tt>.  Section <ref
	      id="printing:printcap" name="The /etc/printcap File">
	      shows you how.
	  </enum>

	<sect2><heading>Kernel Configuration<label
	      id="printing:kernel"></heading>

	  <p> The operating system kernel is compiled to work with a
	    specific set of devices.  The serial or parallel interface
	    for your printer is a part of that set.  Therefore, it
	    might be necessary to add support for an additional serial
	    or parallel port if your kernel is not already configured
	    for one.

	    To find out if the kernel you are currently using supports a serial
	    interface, type
<tscreen>
<tt>dmesg &verbar; grep sio</tt><it/N/
</tscreen>
	    where <it/N/ is the number of the serial port, starting
	    from zero.  If you see output similar to the following
<tscreen><verb> 
sio2 at 0x3e8-0x3ef irq 5 on isa
sio2: type 16550A
</verb></tscreen>
	    then the kernel supports the port.

	    To find out if the kernel supports a parallel interface,
	    type
<tscreen>
<tt>dmesg &verbar; grep lpt</tt><it/N/
</tscreen>
	    where <it/N/ is the number of the parallel port, starting
	    from zero.  If you see output similar to the following
<tscreen><verb>
lpt0 at 0x378-0x37f on isa
</verb></tscreen>
	    then the kernel supports the port.

	    You might have to reconfigure your kernel in order for the
	    operating system to recognize and use the parallel or
	    serial port you are using for the printer.

	    To add support for a serial port, see the section on
            kernel configuration.  To add support for a parallel port,
            see that section <em/and/ the section that follows.

	  <sect3><heading>Adding <tt>/dev</tt> Entries for the Ports
	      <label id="printing:dev-ports"></heading>

	    <p> Even though the kernel may support communication along
	      a serial or parallel port, you will still need a software
	      interface through which programs running on the system
	      can send and receive data.  That is what entries in the
	      <tt>/dev</tt> directory are for.

	      <bf>To add a <tt>/dev</tt> entry for a port:</bf>
	      <enum>
		<item>Become root with the 
		<htmlurl url="http://www.freebsd.org/cgi/man.cgi?su" 
		name="su"> command.  Enter
		  the root password when prompted.

		<item>Change to the <tt>/dev</tt> directory:
<tscreen><verb>
cd /dev
</verb></tscreen>

		<item>Type
<tscreen>
<tt> ./MAKEDEV</tt> <it/port/
</tscreen>
		  where <it/port/ is the device entry for the port you
		  want to make.  Use <tt/lpt0/ for the first parallel
		  port, <tt/lpt1/ for the second, and so on; use
		  <tt/ttyd0/ for the first serial port, <tt/ttyd1/ for
		  the second, and so on.

		<item>Type
<tscreen>
<tt>ls -l</tt> <it/port/
</tscreen>
		  to make sure the device entry got created.
	      </enum>

	  <sect3><heading>Setting the Communication Mode for the Parallel Port
	      <label id="printing:parallel-port-mode"></heading>

	    <p> When you are using the parallel interface, you can
	      choose whether FreeBSD should use interrupt-driven or
	      polled communication with the printer.

	      <itemize>
		<item>The <em/interrupt-driven/ method is the default
		  with the GENERIC kernel.  With this method, the
		  operating system uses an IRQ line to determine when
		  the printer is ready for data.

		<item>The <em/polled/ method directs the operating
		  system to repeatedly ask the printer if it is ready
		  for more data.  When it responds ready, the kernel
		  sends more data.
	      </itemize>

	      The interrupt-driven method is somewhat faster but uses
	      up a precious IRQ line.  You should use whichever one
	      works.

	      You can set the communications mode in two ways: by
	      configuring the kernel or by using the 
	      <htmlurl url="http://www.freebsd.org/cgi/man.cgi?lptcontrol"
	      name="lptcontrol">

	      program.

	      <bf>To set the communications mode by configuring the
		kernel:</bf>
	      <enum>
		<item>Edit your kernel configuration file.  Look for
		  or add an <tt/lpt0/ entry.  If you are setting up the
		  second parallel port, use <tt/lpt1/ instead.  Use
		  <tt/lpt2/ for the third port, and so on.
		  <itemize>
		    <item>If you want interrupt-driven mode, add the <tt/irq/
		      specifier:
<tscreen>
<tt>device lpt0 at isa? port? tty irq <it/N/ vector lptintr</tt>
</tscreen>
		      where <it/N/ is the IRQ number for your
		      computer's parallel port.

		    <item>If you want polled mode, do not add the
		      <tt/irq/ specifier:
<tscreen>
<tt>device lpt0 at isa? port? tty vector lptintr</tt>		
</tscreen>
		  </itemize>
		<item>Save the file.  Then configure, build, and
		  install the kernel, then reboot.  See <ref id="kernelconfig"
		  name="kernel configuration"> for more details.
	      </enum>

	      <bf>To set the communications mode with</bf>
	      <htmlurl url="http://www.freebsd.org/cgi/man.cgi?lptcontrol"
		 name="lptcontrol">:
	      <itemize>
		<item>
		  Type
<tscreen>
<tt>lptcontrol -i -u <it/N/</tt>
</tscreen>
		  to set interrupt-driven mode for <tt/lpt<it/N//.

		<item>
		  Type
<tscreen>
<tt>lptcontrol -p -u <it/N/</tt>
</tscreen>
		  to set polled-mode for <tt/lpt<it/N//.
	      </itemize>
	      You could put these commands in your
	      <tt>/etc/rc.local</tt> file to set the mode each time
	      your system boots.  See 
	      <htmlurl url="http://www.freebsd.org/cgi/man.cgi?lptcontrol(8)"
	      name="lptcontrol(8)"> for more information.

	  <sect3><heading>Checking Printer Communications<label
		id="printing:testing"></heading>

	    <p> Before proceeding to configure the spooling system,
	      you should make sure the operating system can
	      successfully send data to your printer.  It is a lot
	      easier to debug printer communication and the spooling
	      system separately.

	      To test the printer, we will send some text to it.  For
	      printers that can immediately print characters sent to
	      them, the program 
	      <htmlurl url="http://www.freebsd.org/cgi/man.cgi?lptest"
	      name="lptest"> is perfect: it generates
	      all 96 printable ASCII characters in 96 lines.

	      For a PostScript (or other language-based) printer,
	      we will need a more sophisticated test.  A small
	      PostScript program, such as the following, will suffice:
<code>
%!PS
100 100 moveto 300 300 lineto stroke
310 310 moveto
/Helvetica findfont 12 scalefont setfont
(Is this thing working?) show
showpage
</code>
	      <em/Note:/ When this document refers to a printer
	      language, I am assuming a language like PostScript, and
	      not Hewlett Packard's PCL.  Although PCL has great
	      functionality, you can intermingle plain text with its
	      escape sequences.  PostScript cannot directly print
	      plain text, and that is the kind of printer language for
	      which we must make special accommodations.

	    <sect4><heading>Checking a Parallel Printer<label
		  id="printing:checking:parallel"></heading>

	      <p> This section tells you how to check if FreeBSD can
		communicate with a printer connected to a parallel port.

		<bf>To test a printer on a parallel port:</bf>
		<enum>
		  <item>Become root with 
		  <htmlurl url="http://www.freebsd.org/cgi/man.cgi?su"
		  name="su">.
		  <item>Send data to the printer.
		    <itemize>
		      <item>If the printer can print plain text, then
			use <htmlurl url="http://www.freebsd.org/cgi/man.cgi?lptest" 
			name="lptest">. Type:
<tscreen>
<tt>lptest > /dev/lpt<it/N/</tt>
</tscreen>
			where <it/N/ is the number of the parallel
			port, starting from zero.

		      <item>If the printer understands PostScript or
			other printer language, then send a small
			program to the printer.  Type
<tscreen>
<tt>cat > /dev/lpt<it/N/</tt>
</tscreen>
			Then, line by line, type the program
			<em/carefully/ as you cannot edit a line once
			you have pressed RETURN or ENTER. When you have
			finished entering the program, press
			CONTROL+D, or whatever your end of file key
			is.

			<p> Alternatively, you can put the program in
			  a file and type
<tscreen>
<tt>cat <it/file/ > /dev/lpt<it/N/</tt>
</tscreen>
			  where <it/file/ is the name of the file
			  containing the program you want to send to
			  the printer.
		    </itemize>
		</enum>

		You should see something print.  Do not worry if the
		text does not look right; we will fix such things later.

	    <sect4><heading>Checking a Serial Printer<label
		  id="printing:checking:serial"></heading>

	      <p> This section tells you how to check if FreeBSD can
		communicate with a printer on a serial port.

		<bf>To test a printer on a serial port:</bf>
		<enum>
		  <item>Become root with 
		  <htmlurl url="http://www.freebsd.org/cgi/man.cgi?su"
		  name="su">.

		  <item>Edit the file <tt>/etc/remote</tt>.  Add the
		    following entry:
<tscreen>
<tt>printer:dv=/dev/<it/port/:br&num;<it/bps-rate/:pa=<it/parity/</tt>
</tscreen>
		    where <it/port/ is the device entry for the serial
		    port (<tt/ttyd0/, <tt/ttyd1/, etc.), <it/bps-rate/
		    is the bits-per-second rate at which the printer
		    communicates, and <it/parity/ is the parity
		    required by the printer (either <tt/even/,
		    <tt/odd/, <tt/none/, or <tt/zero/).
		    <p>
		      Here is a sample entry for a printer connected
		      via a serial line to the third serial port at
		      19200 bps with no parity:
<code>
printer:dv=/dev/ttyd2:br#19200:pa=none
</code>

		  <item>Connect to the printer with 
		  <htmlurl url="http://www.freebsd.org/cgi/man.cgi?tip"
		  name="tip">.  Type:
<tscreen><verb>
tip printer
</verb></tscreen>
		    If this step does not work, edit the file
		    <tt>/etc/remote</tt> again and try using
		    <tt>/dev/cuaa<it/N/</tt> instead of
		    <tt>/dev/ttyd<it/N/</tt>.

		  <item>Send data to the printer.
		    <itemize>
		      <item>If the printer can print plain text, then
			use 
			<htmlurl url="http://www.freebsd.org/cgi/man.cgi?lptest"
			name="lptest">. Type:
<tscreen><verb>
~$lptest
</verb></tscreen>

		      <item>If the printer understands PostScript or
			other printer language, then send a small
			program to the printer.  Type the program,
			line by line, <em/very carefully/ as
			backspacing or other editing keys may be
			significant to the printer. You may also need
			to type a special end-of-file key for the
			printer so it knows it received the whole
			program.  For PostScript printers, press
			CONTROL+D.

			<p> Alternatively, you can put the program in
			  a file and type
<tscreen>
<tt>&tilde;&gt;<it/file/</tt>
</tscreen>
			  where <it/file/ is the name of the file
			  containing the program.  After 
			  <htmlurl url="http://www.freebsd.org/cgi/man.cgi?tip"
			  name="tip"> sends the file, press any required
			  end-of-file key.
		    </itemize>
		</enum>

		You should see something print.  Do not worry if the
		text does not look right; we will fix that later.

	<sect2><heading>Enabling the Spooler: The <tt>/etc/printcap</tt> File
	    <label id="printing:printcap"></heading>

	  <p> At this point, your printer should be hooked up, your
	    kernel configured to communicate with it (if necessary),
	    and you have been able to send some simple data to the
	    printer.  Now, we are ready to configure LPD to control
	    access to your printer.

	    You configure LPD by editing the file
	    <tt>/etc/printcap</tt>.  The LPD spooling system reads
	    this file each time the spooler is used, so updates to the
	    file take immediate effect.

	    The format of the 
	    <htmlurl url="http://www.freebsd.org/cgi/man.cgi?printcap"
	    name="printcap"> file is straightforward.
	    Use your favorite text editor to make changes to
	    <tt>/etc/printcap</tt>.  The format is identical to other
	    capability files like <tt>/usr/share/misc/termcap</tt> and
	    <tt>/etc/remote</tt>.  For complete information about the
	    format, see the 
	    <htmlurl url="http://www.freebsd.org/cgi/man.cgi?cgetent(3)"
	    name="cgetent(3)">.

	    The simple spooler configuration consists of the following steps:
	    <enum>
	      <item>Pick a name (and a few convenient aliases) for
		the printer, and put them in the
		<tt>/etc/printcap</tt> file; see <ref
		id="printing:naming" name="Naming the Printer">.

	      <item>Turn off header pages (which are on by default)
		by inserting the <tt/sh/ capability; see <ref
		id="printing:no-header-pages" name="Suppressing Header
		Pages">.

	      <item>Make a spooling directory, and specify its
		location with the <tt/sd/ capability; see <ref
		id="printing:spooldir" name="Making the Spooling
		Directory">.

	      <item>Set the <tt>/dev</tt> entry to use for the
		printer, and note it in <tt>/etc/printcap</tt> with
		the <tt/lp/ capability; see <ref id="printing:device"
		name="Identifying the Printer Device">.  Also, if the
		printer is on a serial port, set up the communication
		parameters with the <tt/fs/, <tt/fc/, <tt/xs/, and
		<tt/xc/ capabilities; see <ref id="printing:commparam"
		name="Configuring Spooler Communications Parameters">.

	      <item>Install a plain text input filter; see <ref
		  id="printing:textfilter" name="Installing the Text
		  Filter">

	      <item>Test the setup by printing something with the
		
		<htmlurl url="http://www.freebsd.org/cgi/man.cgi?lpr"
		name="lpr"> command; see <ref id="printing:trying"
		name="Trying It Out"> and <ref
		id="printing:troubleshooting" name="Troubleshooting">.
	    </enum>

	    <em/Note:/ Language-based printers, such as PostScript
	    printers, cannot directly print plain text.  The simple
	    setup outlined above and described in the following
	    sections assumes that if you are installing such a printer
	    you will print only files that the printer can understand.

	    Users often expect that they can print plain text to any
	    of the printers installed on your system.  Programs that
	    interface to LPD to do their printing usually make the
	    same assumption.  If you are installing such a printer and
	    want to be able to print jobs in the printer language
	    <em/and/ print plain text jobs, you are strongly urged to
	    add an additional step to the simple setup outlined above:
	    install an automatic plain-text--to--PostScript (or other
	    printer language) conversion program.  Section <ref
	    id="printing:advanced:if-conversion" name="Accommodating
	    Plain Text Jobs on PostScript Printers"> tells how to do
	    this.

	  <sect3><heading>Naming the Printer<label
		id="printing:naming"></heading>

	    <p> The first (easy) step is to pick a name for your
	      printer.  It really does not matter whether you choose
	      functional or whimsical names since you can also provide
	      a number aliases for the printer.

	      At least one of the printers specified in the
	      <tt>/etc/printcap</tt> should have the alias
	      <tt/lp/. This is the default printer's name.  If users
	      do not have the PRINTER environment variable nor
	      specify a printer name on the command line of any of the
	      LPD commands, then <tt/lp/ will be the default printer
	      they get to use.

	      Also, it is common practice to make the last alias for a
	      printer be a full description of the printer, including
	      make and model.

	      Once you have picked a name and some common aliases, put
	      them in the <tt>/etc/printcap</tt> file.  The name of
	      the printer should start in the leftmost column.
	      Separate each alias with a vertical bar and put a colon
	      after the last alias.

	      In the following example, we start with a skeletal
	      <tt>/etc/printcap</tt> that defines two printers (a
	      Diablo 630 line printer and a Panasonic KX-P4455
	      PostScript laser printer):
<code>
#
#  /etc/printcap for host rose
#
rattan|line|diablo|lp|Diablo 630 Line Printer:

bamboo|ps|PS|S|panasonic|Panasonic KX-P4455 PostScript v51.4:
</code>
	      In this example, the first printer is named <tt/rattan/
	      and has as aliases <tt/line/, <tt/diablo/, <tt/lp/, and
	      <tt/Diablo 630 Line Printer/.  Since it has the alias
	      <tt/lp/, it is also the default printer.  The second is
	      named <tt/bamboo/, and has as aliases <tt/ps/, <tt/PS/,
	      <tt/S/, <tt/panasonic/, and <tt/Panasonic KX-P4455
	      PostScript v51.4/.

	  <sect3><heading>Suppressing Header Pages<label
		id="printing:no-header-pages"></heading>

	    <p> The LPD spooling system will by default print a
	      <em/header page/ for each job.  The header page contains
	      the user name who requested the job, the host from which
	      the job came, and the name of the job, in nice large
	      letters.  Unfortunately, all this extra text gets in the
	      way of debugging the simple printer setup, so we will
	      suppress header pages.

	      To suppress header pages, add the <tt/sh/ capability to
	      the entry for the printer in
	      <tt>/etc/printcap</tt>. Here is the example
	      <tt>/etc/printcap</tt> with <tt/sh/ added:
<code>
#
#  /etc/printcap for host rose - no header pages anywhere
#
rattan|line|diablo|lp|Diablo 630 Line Printer:\
	:sh:

bamboo|ps|PS|S|panasonic|Panasonic KX-P4455 PostScript v51.4:\
	:sh:
</code>
	      Note how we used the correct format: the first line
	      starts in the leftmost column, and subsequent lines are
	      indented with a single TAB.  Every line in an entry
	      except the last ends in a backslash character.

	  <sect3><heading>Making the Spooling Directory<label
		id="printing:spooldir"></heading>

	    <p> The next step in the simple spooler setup is to make a
	      <em/spooling directory/, a directory where print jobs
	      reside until they are printed, and where a number of
	      other spooler support files live.

	      Because of the variable nature of spooling directories,
	      it is customary to put these directories under
	      <tt>/var/spool</tt>.  It is not necessary to backup the
	      contents of spooling directories, either.  Recreating
	      them is as simple as running 
	      <htmlurl url="http://www.freebsd.org/cgi/man.cgi?mkdir"
	      name="mkdir">.

	      It is also customary to make the directory with a name
	      that is identical to the name of the printer, as shown
	      below:
<tscreen>
<tt>mkdir /var/spool/<it>printer-name</it></tt>
</tscreen>
	      However, if you have a lot of printers on your network,
	      you might want to put the spooling directories under a
	      single directory that you reserve just for printing with
	      LPD.  We will do this for our two example printers
	      <tt/rattan/ and <tt/bamboo/:
<tscreen><verb>
mkdir /var/spool/lpd
mkdir /var/spool/lpd/rattan
mkdir /var/spool/lpd/bamboo
</verb></tscreen>

	      <em/Note:/ If you are concerned about the privacy of jobs
	      that users print, you might want to protect the spooling
	      directory so it is not publicly accessible.  Spooling
	      directories should be owned and be readable, writable,
	      and searchable by user daemon and group daemon, and no
	      one else.  We will do this for our example printers:

<tscreen><verb>
chown daemon.daemon /var/spool/lpd/rattan
chown daemon.daemon /var/spool/lpd/bamboo
chmod 770 /var/spool/lpd/rattan
chmod 770 /var/spool/lpd/bamboo
</verb></tscreen>

	      Finally, you need to tell LPD about these directories
	      using the <tt>/etc/printcap</tt> file.  You specify the
	      pathname of the spooling directory with the <tt/sd/
	      capability:
<code>
#
#  /etc/printcap for host rose - added spooling directories
#
rattan|line|diablo|lp|Diablo 630 Line Printer:\
	:sh:sd=/var/spool/lpd/rattan:

bamboo|ps|PS|S|panasonic|Panasonic KX-P4455 PostScript v51.4:\
	:sh:sd=/var/spool/lpd/bamboo:
</code>
	      Note that the name of the printer starts in the first
	      column but all other entries describing the printer
	      should be indented with a tab and each line escaped with
	      a backslash.

	      If you do not specify a spooling directory with <tt/sd/,
	      the spooling system will use <tt>/var/spool/lpd</tt> as
	      a default.

	  <sect3><heading>Identifying the Printer Device<label
		id="printing:device"></heading>

	    <p> In section <ref id="printing:dev-ports" name="Adding
		/dev Entries for the Ports">, we identified which
	      entry in the <tt>/dev</tt> directory FreeBSD will use
	      to communicate with the printer.  Now, we tell LPD
	      that information.  When the spooling system has a job
	      to print, it will open the specified device on behalf
	      of the filter program (which is responsible for
	      passing data to the printer).

	      List the <tt>/dev</tt> entry pathname in the
	      <tt>/etc/printcap</tt> file using the <tt/lp/
	      capability.

	      In our running example, let us assume that <tt/rattan/ is
	      on the first parallel port, and <tt/bamboo/ is on a
	      sixth serial port; here are the additions to
	      <tt>/etc/printcap</tt>:
<code>
#
#  /etc/printcap for host rose - identified what devices to use
#
rattan|line|diablo|lp|Diablo 630 Line Printer:\
	:sh:sd=/var/spool/lpd/rattan:\
	:lp=/dev/lpt0:

bamboo|ps|PS|S|panasonic|Panasonic KX-P4455 PostScript v51.4:\
	:sh:sd=/var/spool/lpd/bamboo:\
	:lp=/dev/ttyd5:
</code>

	      If you do not specify the <tt/lp/ capability for a
	      printer in your <tt>/etc/printcap</tt> file, LPD uses
	      <tt>/dev/lp</tt> as a default.  <tt>/dev/lp</tt>
	      currently does not exist in FreeBSD.

	      If the printer you are installing is connected to a
	      parallel port, skip to the section <ref name="Installing
	      the Text Filter" id="printing:textfilter">.  Otherwise,
	      be sure to follow the instructions in the next section.

	  <sect3><heading>Configuring Spooler Communication
	      Parameters<label id="printing:commparam"></heading>

	    <p> For printers on serial ports, LPD can set up the bps
	      rate, parity, and other serial communication parameters
	      on behalf of the filter program that sends data to the
	      printer.  This is advantageous since
	      <itemize>
		<item>It lets you try different communication
		  parameters by simply editing the
		  <tt>/etc/printcap</tt> file; you do not have to
		  recompile the filter program.

		<item>It enables the spooling system to use the same
		  filter program for multiple printers which may have
		  different serial communication settings.
	      </itemize>

	      The following <tt>/etc/printcap</tt> capabilities
	      control serial communication parameters of the device
	      listed in the <tt/lp/ capability:
	      <descrip>
		<tag/<tt>br&num;<it/bps-rate/</tt>/

		  Sets the communications speed of the device to
		  <it/bps-rate/, where <it/bps-rate/ can be 50, 75,
		  110, 134, 150, 200, 300, 600, 1200, 1800, 2400,
		  4800, 9600, 19200, or 38400 bits-per-second.

		<tag/<tt>fc&num;<it/clear-bits/</tt>/

		  Clears the flag bits <it/clear-bits/ in the
		  <tt/sgttyb/ structure after opening the device.

		<tag/<tt>fs&num;<it/set-bits/</tt>/

		  Sets the flag bits <it/set-bits/ in the <tt/sgttyb/
		  structure.

		<tag/<tt>xc&num;<it/clear-bits/</tt>/

		  Clears local mode bits <it/clear-bits/ after opening
		  the device.

		<tag/<tt>xs&num;<it/set-bits/</tt>/

		  Sets local mode bits <it/set-bits/.
	      </descrip>
	      For more information on the bits for the <tt/fc/,
	      <tt/fs/, <tt/xc/, and <tt/xs/ capabilities, see the file
	      <tt>/usr/include/sys/ioctl_compat.h</tt>.

	      When LPD opens the device specified by the <tt/lp/
	      capability, it reads the flag bits in the <tt/sgttyb/
	      structure; it clears any bits in the <tt/fc/ capability,
	      then sets bits in the <tt/fs/ capability, then applies
	      the resultant setting.  It does the same for the local
	      mode bits as well.

	      Let us add to our example printer on the sixth serial
	      port.  We will set the bps rate to 38400. For the flag
	      bits, we will set the TANDEM, ANYP, LITOUT, FLUSHO, and
	      PASS8 flags.  For the local mode bits, we will set the
	      LITOUT and PASS8 flags:
<tscreen><verb>
bamboo|ps|PS|S|panasonic|Panasonic KX-P4455 PostScript v51.4:\
	:sh:sd=/var/spool/lpd/bamboo:\
	:lp=/dev/ttyd5:fs#0x82000c1:xs#0x820:
</verb></tscreen>


	  <sect3><heading>Installing the Text Filter<label
		id="printing:textfilter"></heading>

	    <p> We are now ready to tell LPD what text filter to use to
	      send jobs to the printer.  A <em/text filter/, also
	      known as an <em/input filter/, is a program that LPD
	      runs when it has a job to print.  When LPD runs the text
	      filter for a printer, it sets the filter's standard
	      input to the job to print, and its standard output to
	      the printer device specified with the <tt/lp/
	      capability.  The filter is expected to read the job from
	      standard input, perform any necessary translation for the
	      printer, and write the results to standard output, which
	      will get printed.  For more information on the text
	      filter, see section <ref id="printing:advanced:filters"
	      name="Filters">.

	      For our simple printer setup, the text filter can be a
	      small shell script that just executes <tt>/bin/cat</tt>
	      to send the job to the printer.  FreeBSD comes with
	      another filter called <tt/lpf/ that handles backspacing
	      and underlining for printers that might not deal with
	      such character streams well.  And, of course, you can
	      use any other filter program you want.  The filter
	      <tt/lpf/ is described in detail in section <ref
	      id="printing:advanced:lpf" name="lpf: a Text Filter">.

	      First, let us make the shell script
	      <tt>/usr/local/libexec/if-simple</tt> be a simple text
	      filter. Put the following text into that file with your
	      favorite text editor:
<code>
#!/bin/sh
#
# if-simple - Simple text input filter for lpd
# Installed in /usr/local/libexec/if-simple
#
# Simply copies stdin to stdout.  Ignores all filter arguments.

/bin/cat &amp;&amp; exit 0
exit 2
</code>
	      Make the file executable:
<tscreen><verb>
chmod 555 /usr/local/libexec/if-simple
</verb></tscreen>

	      And then tell LPD to use it by specifying it with the
	      <tt/if/ capability in <tt>/etc/printcap</tt>.  We will add
	      it to the two printers we have so far in the example
	      <tt>/etc/printcap</tt>:
<code>
#
#  /etc/printcap for host rose - added text filter
#
rattan|line|diablo|lp|Diablo 630 Line Printer:\
	:sh:sd=/var/spool/lpd/rattan:\
	:lp=/dev/lpt0:\
	:if=/usr/local/libexec/if-simple:

bamboo|ps|PS|S|panasonic|Panasonic KX-P4455 PostScript v51.4:\
	:sh:sd=/var/spool/lpd/bamboo:\
	:lp=/dev/ttyd5:fs#0x82000e1:xs#0x820:\
	:if=/usr/local/libexec/if-simple:
</code>

	  <sect3><heading>Trying It Out<label id="printing:trying"></heading>

	    <p> You have reached the end of the simple LPD setup.
	      Unfortunately, congratulations are not quite yet in
	      order, since we still have to test the setup and
	      correct any problems.  To test the setup, try printing
	      something.  To print with the LPD system, you use the
	      command 
	      <htmlurl url="http://www.freebsd.org/cgi/man.cgi?lpr"
	      name="lpr">, which submits a job for printing.

	      You can combine 
	      <htmlurl url="http://www.freebsd.org/cgi/man.cgi?lpr"
	      name="lpr"> with the 
	      <htmlurl url="http://www.freebsd.org/cgi/man.cgi?lptest"
	      name="lptest"> program,
	      introduced in section <ref id="printing:testing"
	      name="Checking Printer Communications"> to generate some
	      test text.

	      <bf>To test the simple LPD setup:</bf>

	    <p> Type:
<tscreen>
<tt>lptest 20 5 | lpr -P<it/printer-name/</tt>
</tscreen>
	      where <it/printer-name/ is a the name of a printer (or
	      an alias) specified in <tt>/etc/printcap</tt>.  To test
	      the default printer, type 
	      <htmlurl url="http://www.freebsd.org/cgi/man.cgi?lpr"
	      name="lpr"> without any <tt/-P/
	      argument.  Again, if you are testing a printer that
	      expects PostScript, send a PostScript program in that
	      language instead of using 
	      <htmlurl url="http://www.freebsd.org/cgi/man.cgi?lptest"
	      name="lptest">.  You can do so by
	      putting the program in a file and typing <tt/lpr
	      <it/file//.

	      For a PostScript printer, you should get the results
	      of the program.  If you are using 
	      <htmlurl url="http://www.freebsd.org/cgi/man.cgi?lptest"
	      name="lptest">, then your
	      results should look like the following:

<tscreen><verb>
!"#$%&amp;'()*+,-./01234
"#$%&amp;'()*+,-./012345
#$%&amp;'()*+,-./0123456
$%&amp;'()*+,-./01234567
%&amp;'()*+,-./012345678
</verb></tscreen>

	      To further test the printer, try downloading larger
	      programs (for language-based printers) or running
	      
	      <htmlurl url="http://www.freebsd.org/cgi/man.cgi?lptest"
	      name="lptest"> with different arguments.  For example,
	      <tt/lptest 80 60/ will produce 60 lines of 80 characters
	      each.

	      If the printer did not work, see the next section, <ref
		id="printing:troubleshooting" name="Troubleshooting">.

	  <sect3><heading>Troubleshooting<label
		id="printing:troubleshooting"></heading>

	    <p> After performing the simple test with 
	    <htmlurl url="http://www.freebsd.org/cgi/man.cgi?lptest"
	    name="lptest">, you
	      might have gotten one of the following results instead of
	      the correct printout:
	      <descrip>
		<tag/It worked, after awhile; or, it did not eject a full sheet./

		  The printer printed the above, but it sat for awhile
		  and did nothing.  In fact, you might have needed to
		  press a PRINT REMAINING or FORM FEED button on the
		  printer to get any results to appear.

		  If this is the case, the printer was probably
		  waiting to see if there was any more data for your
		  job before it printed anything.  To fix this
		  problem, you can have the text filter send a FORM
		  FEED character (or whatever is necessary) to the
		  printer.  This is usually sufficient to have the
		  printer immediately print any text remaining in its
		  internal buffer.  It is also useful to make sure each
		  print job ends on a full sheet, so the next job
		  does not start somewhere on the middle of the last
		  page of the previous job.

		  The following replacement for the shell script
		  <tt>/usr/local/libexec/if-simple</tt> prints a form
		  feed after it sends the job to the printer:
<code>
#!/bin/sh
#
# if-simple - Simple text input filter for lpd
# Installed in /usr/local/libexec/if-simple
#
# Simply copies stdin to stdout.  Ignores all filter arguments.
# Writes a form feed character (\f) after printing job.

/bin/cat &amp;&amp; printf "\f" &amp;&amp; exit 0
exit 2
</code>

		<tag/It produced the ``staircase effect.''/

		  You got the following on paper:
<tscreen><verb>
!"#$%&amp;'()*+,-./01234
                        "#$%&amp;'()*+,-./012345
                                                #$%&amp;'()*+,-./0123456
</verb></tscreen>
		  You have become another victim of the <em/staircase
		  effect/, caused by conflicting interpretations of
		  what characters should indicate a new-line.
		  UNIX-style operating systems use a single character:
		  ASCII code 10, the line feed (LF).  MS-DOS, OS/2,
		  and others uses a pair of characters, ASCII code 10
		  <em/and/ ASCII code 13 (the carriage return or CR).
		  Many printers use the MS-DOS convention for
		  representing new-lines.

		  When you print with FreeBSD, your text used just the
		  line feed character.  The printer, upon seeing a
		  line feed character, advanced the paper one line,
		  but maintained the same horizontal position on the
		  page for the next character to print.  That is what
		  the carriage return is for: to move the location of
		  the next character to print to the left edge of the
		  paper.

		  Here is what FreeBSD wants your printer to do:
<tscreen><verb>
Printer received CR		Printer prints CR
Printer received LF		Printer prints CR + LF
</verb></tscreen>
		  
		  Here are some ways to achieve this:
		  <itemize>
		    <item>Use the printer's configuration switches or
		      control panel to alter its interpretation of
		      these characters.  Check your printer's manual
		      to find out how to do this.

		      <p> <em/Note:/ If you boot your system into
			other operating systems besides FreeBSD, you
			may have to <em/reconfigure/ the printer to
			use a an interpretation for CR and LF
			characters that those other operating systems
			use.  You might prefer one of the other
			solutions, below.

		    <item>Have FreeBSD's serial line driver
		      automatically convert LF to CR+LF. Of course,
		      this works with printers on serial ports
		      <em/only/.  To enable this feature, set the
		      CRMOD bit in <tt/fs/ capability in the
		      <tt>/etc/printcap</tt> file for the printer.

		    <item>Send an <em/escape code/ to the printer to
		      have it temporarily treat LF characters
		      differently.  Consult your printer's manual for
		      escape codes that your printer might support.
		      When you find the proper escape code, modify the
		      text filter to send the code first, then send
		      the print job.

		      <p> Here is an example text filter for printers
			that understand the Hewlett-Packard PCL escape
			codes.  This filter makes the printer treat LF
			characters as a LF and CR; then it sends the
			job; then it sends a form feed to eject the
			last page of the job.  It should work with
			nearly all Hewlett Packard printers.

<code>
#!/bin/sh
#
# hpif - Simple text input filter for lpd for HP-PCL based printers
# Installed in /usr/local/libexec/hpif
#
# Simply copies stdin to stdout.  Ignores all filter arguments.
# Tells printer to treat LF as CR+LF. Writes a form feed character
# after printing job.

printf "\033&amp;k2G" &amp;&amp; cat &amp;&amp; printf "\f" &amp;&amp; exit 0
exit 2
</code>

			Here is an example <tt>/etc/printcap</tt> from
			a host called orchid.  It has a single printer
			attached to its first parallel port, a Hewlett
			Packard LaserJet 3Si named <tt/teak/.  It is
			using the above script as its text filter:
<code>
#
#  /etc/printcap for host orchid
#
teak|hp|laserjet|Hewlett Packard LaserJet 3Si:\
	:lp=/dev/lpt0:sh:sd=/var/spool/lpd/teak:mx#0:\
	:if=/usr/local/libexec/hpif:
</code>
		  </itemize>

		<tag/It overprinted each line./

		  The printer never advanced a line.  All of the lines
		  of text were printed on top of each other on one
		  line.

		  This problem is the ``opposite'' of the staircase
		  effect, described above, and is much rarer.
		  Somewhere, the LF characters that FreeBSD uses to
		  end a line are being treated as CR characters to
		  return the print location to the left edge of the
		  paper, but not also down a line.

		  Use the printer's configuration switches or control
		  panel to enforce the following interpretation of LF
		  and CR characters:
<tscreen><verb>
Printer received CR		Printer prints CR
Printer received LF		Printer prints CR + LF
</verb></tscreen>

		<tag/The printer lost characters./

		  While printing, the printer did not print a few
		  characters in each line.  The problem might have
		  gotten worse as the printer ran, losing more and
		  more characters.

		  The problem is that the printer cannot keep up with
		  the speed at which the computer sends data over a
		  serial line.  (This problem should not occur with
		  printers on parallel ports.)  There are two ways to
		  overcome the problem:
		  <itemize>
		    <item>If the printer supports XON/XOFF flow
		      control, have FreeBSD use it by specifying the
		      TANDEM bit in the <tt/fs/ capability.

		    <item>If the printer supports carrier flow
		      control, specify the MDMBUF bit in the <tt/fs/
		      capability.  Make sure the cable connecting the
		      printer to the computer is correctly wired for
		      carrier flow control.

		    <item>If the printer does not support any flow
		      control, use some combination of the NLDELAY,
		      TBDELAY, CRDELAY, VTDELAY, and BSDELAY bits in
		      the <tt/fs/ capability to add appropriate delays
		      to the stream of data sent to the printer.
		  </itemize>

		<tag/It printed garbage./

		  The printer printed what appeared to be random
		  garbage, but not the desired text.

		  This is usually another symptom of incorrect
		  communications parameters with a serial printer.
		  Double-check the bps rate in the <tt/br/ capability,
		  and the parity bits in the <tt/fs/ and <tt/fc/
		  capabilities; make sure the printer is using the
		  same settings as specified in the
		  <tt>/etc/printcap</tt> file.

		<tag/Nothing happened./

		  If nothing happened, the problem is probably within
		  FreeBSD and not the hardware.  Add the log file
		  (<tt/lf/) capability to the entry for the printer
		  you are debugging in the <tt>/etc/printcap</tt> file.
		  For example, here is the entry for <tt/rattan/, with
		  the <tt/lf/ capability:
<tscreen><verb>
rattan|line|diablo|lp|Diablo 630 Line Printer:\
	:sh:sd=/var/spool/lpd/rattan:\
	:lp=/dev/lpt0:\
	:if=/usr/local/libexec/if-simple:\
	:lf=/var/log/rattan.log
</verb></tscreen>
		  Then, try printing again.  Check the log file (in
		  our example, <tt>/var/log/rattan.log</tt>) to see
		  any error messages that might appear.  Based on the
		  messages you see, try to correct the problem.

		  If you do not specify a <tt/lf/ capability, LPD uses
		  <tt>/dev/console</tt> as a default.
	      </descrip>

    <sect><heading>Using Printers<label id="printing:using"></heading>

      <p> This section tells you how to use printers you have setup with
	FreeBSD.  Here is an overview of the user-level commands:
	<descrip>
	  <tag><htmlurl url="http://www.freebsd.org/cgi/man.cgi?lpr"
	  name="lpr"></tag> Print jobs

	  <tag><htmlurl url="http://www.freebsd.org/cgi/man.cgi?lpq"
	   name="lpq"></tag> Check printer queues

	  <tag><htmlurl url="http://www.freebsd.org/cgi/man.cgi?lprm"
	   name="lprm"></tag> Remove jobs from a printer's queue

	</descrip>

	There is also an administrative command, 
	<htmlurl url="http://www.freebsd.org/cgi/man.cgi?lpc"
	name="lpc">, described in
	the section <ref id="printing:lpc" name="Administrating the
	LPD Spooler">, used to control printers and their queues.

	All three of the commands 
	<htmlurl url="http://www.freebsd.org/cgi/man.cgi?lpr"
	 name="lpr">, 
	 <htmlurl url="http://www.freebsd.org/cgi/man.cgi?lprm"
	  name="lprm">, and 
	  <htmlurl url="http://www.freebsd.org/cgi/man.cgi?lpq"
	   name="lpq">
	accept an option ``<tt/-P/ <it/printer-name/'' to specify on
	which printer/queue to operate, as listed in the
	<tt>/etc/printcap</tt> file.  This enables you to submit,
	remove, and check on jobs for various printers.  If you do not
	use the <tt/-P/ option, then these commands use the printer
	specified in the PRINTER environment variable.  Finally, if
	you do not have a PRINTER environment variable, these commands
	default to the printer named <tt/lp/.

	Hereafter, the terminology <em/default printer/ means the
	printer named in the PRINTER environment variable, or the
	printer named <tt/lp/ when there is no PRINTER environment
	variable.

      <sect1><heading>Printing Jobs<label id="printing:lpr"></heading>
	<p>

	  To print files, type
<tscreen>
<tt>lpr <it/filename.../</tt>
</tscreen>
	  This prints each of the listed files to the default printer.
	  If you list no files, 
	  <htmlurl url="http://www.freebsd.org/cgi/man.cgi?lpr"
	  name="lpr"> reads data to print from
	  standard input.  For example, this command prints some
	  important system files:
<tscreen><verb>
lpr /etc/host.conf /etc/hosts.equiv
</verb></tscreen>
	  To select a specific printer, type
<tscreen>
<tt>lpr -P <it/printer-name/ <it/filename.../</tt>
</tscreen>
	  This example prints a long listing of the current directory
	  to the printer named <tt/rattan/:
<tscreen><verb>
ls -l | lpr -P rattan
</verb></tscreen>
	  Because no files were listed for the 
	  <htmlurl url="http://www.freebsd.org/cgi/man.cgi?lpr"
	   name="lpr"> command,
	  <tt/lpr/ read the data to print from standard input, which
	  was the output of the <tt/ls -l/ command.

	  The <htmlurl url="http://www.freebsd.org/cgi/man.cgi?lpr"
	   name="lpr"> command can also accept a wide variety of
	  options to control formatting, apply file conversions,
	  generate multiple copies, and so forth.  For more
	  information, see the section <ref id="printing:lpr:options"
	  name="Printing Options">.

      <sect1><heading>Checking Jobs<label id="printing:lpq"></heading>

	<p> When you print with 
	<htmlurl url="http://www.freebsd.org/cgi/man.cgi?lpr"
	 name="lpr">, the data you wish to print
	  is put together in a package called a <em/print job/, which
	  is sent to the LPD spooling system.  Each printer has a
	  queue of jobs, and your job waits in that queue along with
	  other jobs from yourself and from other users. The printer
	  prints those jobs in a first-come, first-served order.

	  To display the queue for the default printer, type 
	  <htmlurl url="http://www.freebsd.org/cgi/man.cgi?lpq"
	   name="lpq">.
	  For a specific printer, use the <tt/-P/ option.  For
	  example, the command
<tscreen><verb>
lpq -P bamboo
</verb></tscreen>
	  shows the queue for the printer named <tt/bamboo/.  Here is
	  an example of the output of the <tt/lpq/ command:
<tscreen><verb>
bamboo is ready and printing
Rank  Owner	Job  Files				Total Size
active kelly    9    /etc/host.conf, /etc/hosts.equiv   88 bytes
2nd    kelly    10   (standard input)                   1635 bytes
3rd    mary     11   ...                                78519 bytes
</verb></tscreen>
	  This shows three jobs in the queue for <tt/bamboo/.  The
	  first job, submitted by user kelly, got assigned <em/job
	  number/ 9.  Every job for a printer gets a unique job
	  number.  Most of the time you can ignore the job number, but
	  you will need it if you want to cancel the job; see section
	  <ref id="printing:lprm" name="Removing Jobs"> for details.

	  Job number nine consists of two files; multiple files given
	  on the 
	  <htmlurl url="http://www.freebsd.org/cgi/man.cgi?lpr"
	   name="lpr"> command line are treated as part of a single
	  job.  It is the currently active job (note the word
	  <tt/active/ under the ``Rank'' column), which means the
	  printer should be currently printing that job.  The second
	  job consists of data passed as the standard input to the
	  
	  <htmlurl url="http://www.freebsd.org/cgi/man.cgi?lpr"
	   name="lpr"> command. The third job came from user mary; it is a
	  much larger job.  The pathname of the files she's trying to
	  print is too long to fit, so the 
	  <htmlurl url="http://www.freebsd.org/cgi/man.cgi?lpq"
	   name="lpq"> command just shows
	  three dots.

	  The very first line of the output from 
	  <htmlurl url="http://www.freebsd.org/cgi/man.cgi?lpq"
	   name="lpq"> is also
	  useful: it tells what the printer is currently doing (or at
	  least what LPD thinks the printer is doing).

	  The 
	  <htmlurl url="http://www.freebsd.org/cgi/man.cgi?lpq"
	   name="lpq"> command also support a <tt/-l/ option to
	  generate a detailed long listing. Here is an example of
	  <tt/lpq -l/:
<tscreen><verb>
waiting for bamboo to become ready (offline ?)

kelly: 1st				 [job 009rose]
       /etc/host.conf			 73 bytes
       /etc/hosts.equiv		         15 bytes

kelly: 2nd				 [job 010rose]
       (standard input)		         1635 bytes

mary: 3rd				 [job 011rose]
      /home/orchid/mary/research/venus/alpha-regio/mapping 78519 bytes
</verb></tscreen>

      <sect1><heading>Removing Jobs<label
	    id="printing:lprm"></heading>

	<p> If you change your mind about printing a job, you can
	  remove the job from the queue with the 
	  <htmlurl url="http://www.freebsd.org/cgi/man.cgi?lprm"
	   name="lprm"> command.
	  Often, you can even use 
	  <htmlurl url="http://www.freebsd.org/cgi/man.cgi?lprm"
	   name="lprm"> to remove an active job,
	  but some or all of the job might still get printed.

	  To remove a job from the default printer, first use 
	  <htmlurl url="http://www.freebsd.org/cgi/man.cgi?lpq"
	   name="lpq"> to find the job number.  Then type
<tscreen>
<tt/lprm <it/job-number//
</tscreen>
	  To remove the job from a specific printer, add the <tt/-P/
	  option.  The following command removes job number 10 from
	  the queue for the printer <tt/bamboo/:
<tscreen><verb>
lprm -P bamboo 10
</verb></tscreen>
	  The 
	  <htmlurl url="http://www.freebsd.org/cgi/man.cgi?lprm"
	   name="lprm"> command has a few shortcuts:
	  <descrip>
	    <tag/lprm -/

	      Removes all jobs (for the default printer) belonging to
	      you.

	    <tag/lprm <it/user//

	      Removes all jobs (for the default printer) belonging to
	      <it/user/.  The superuser can remove other users' jobs;
	      you can remove only your own jobs.

	    <tag/lprm/

	      With no job number, user name, or ``<tt/-/'' appearing
	      on the command line, 
	      <htmlurl url="http://www.freebsd.org/cgi/man.cgi?lprm"
	       name="lprm"> removes the currently
	      active job on the default printer, if it belongs to
	      you. The superuser can remove any active job.
	  </descrip>

	  Just use the <tt/-P/ option with the above shortcuts to
	  operate on a specific printer instead of the default.  For
	  example, the following command removes all jobs for the
	  current user in the queue for the printer named <tt/rattan/:

<tscreen><verb>
lprm -P rattan -
</verb></tscreen>

	  <em/Note:/ If you are working in a networked environment,
	  
	  <htmlurl url="http://www.freebsd.org/cgi/man.cgi?lprm"
	   name="lprm"> will let you remove jobs only from the host from
	  which the jobs were submitted, even if the same printer is
	  available from other hosts.  The following command sequence
	  demonstrates this:
<code>
rose% lpr -P rattan myfile
rose% rlogin orchid
orchid% lpq -P rattan
Rank   Owner	  Job  Files				     Total Size
active seeyan	  12	...				     49123 bytes
2nd    kelly	  13   myfile				     12 bytes
orchid% lprm -P rattan 13
rose: Permission denied
orchid% logout
rose% lprm -P rattan 13
dfA013rose dequeued
cfA013rose dequeued
rose% 
</code>

      <sect1><heading>Beyond Plain Text: Printing Options<label
	    id="printing:lpr:options"></heading>

      <p> The 
      <htmlurl url="http://www.freebsd.org/cgi/man.cgi?lpr"
       name="lpr"> command supports a number of options that
	  control formatting text, converting graphic and other file
	  formats, producing multiple copies, handling of the job, and
	  more.  This section describes the options.

	<sect2><heading>Formatting and Conversion Options<label
	      id="printing:lpr:options:format"></heading>

	  <p> The following 
	  <htmlurl url="http://www.freebsd.org/cgi/man.cgi?lpr"
	   name="lpr"> options control formatting of the
	    files in the job.  Use these options if the job does not
	    contain plain text or if you want plain text formatted
	    through the 
	    <htmlurl url="http://www.freebsd.org/cgi/man.cgi?pr"
	     name="pr"> utility.

	    For example, the following command prints a DVI file (from
	    the TeX typesetting system) named <tt/fish-report.dvi/
	    to the printer named <tt/bamboo/: 
<tscreen><verb>
lpr -P bamboo -d fish-report.dvi
</verb></tscreen>
	    These options apply to every file in the job, so you cannot
	    mix (say) DVI and ditroff files together in a job.
	    Instead, submit the files as separate jobs, using a
	    different conversion option for each job.

	    <em/Note:/ All of these options except <tt/-p/ and <tt/-T/
	    require conversion filters installed for the destination
	    printer.  For example, the <tt/-d/ option requires the DVI
	    conversion filter.  Section <ref
	    id="printing:advanced:convfilters" name="Conversion
	    Filters"> gives details.
	    
	    <descrip>
	      <tag/<tt/-c// Print cifplot files.

	      <tag/<tt/-d// Print DVI files.

	      <tag/<tt/-f// Print FORTRAN text files.

	      <tag/<tt/-g// Print plot data.

	      <tag/<tt/-i <it/number///

		Indent the output by <it/number/ columns; if you omit
		<it/number/, indent by 8 columns.  This option works
		only with certain conversion filters.

		<em/Note:/ Do not put any space between the <tt/-i/ and
		the number.

	      <tag/<tt/-l//

		Print literal text data, including control characters.

	      <tag/<tt/-n// Print ditroff (device independent troff) data.

	      <tag/-p/

		Format plain text with 
		<htmlurl url="http://www.freebsd.org/cgi/man.cgi?pr"
		 name="pr"> before printing.  See
		<htmlurl url="http://www.freebsd.org/cgi/man.cgi?pr(1)"
		name="pr(1)"> for more information.

	      <tag/<tt/-T <it/title///

		Use <it/title/ on the 
		<htmlurl url="http://www.freebsd.org/cgi/man.cgi?pr"
 name="pr">
 header instead of the
		file name.  This option has effect only when used with
		the <tt/-p/ option.

	      <tag/<tt/-t// Print troff data.

	      <tag/<tt/-v// Print raster data.

	    </descrip>
		
	    Here is an example: this command prints a nicely
	    formatted version of the 
	    <htmlurl url="http://www.freebsd.org/cgi/man.cgi?ls"
	    name="ls"> manual page on the
	    default printer:
<tscreen><verb>
zcat /usr/share/man/man1/ls.1.gz | troff -t -man | lpr -t
</verb></tscreen>
	    The 
	    <htmlurl url="http://www.freebsd.org/cgi/man.cgi?zcat"
	     name="zcat"> command uncompresses the source of the
	    
	    <htmlurl url="http://www.freebsd.org/cgi/man.cgi?ls"
	     name="ls"> manual page and passes it to the 
	     <htmlurl url="http://www.freebsd.org/cgi/man.cgi?troff"
	      name="troff">
	    command, which formats that source and makes GNU troff
	    output and passes it to 
	    <htmlurl url="http://www.freebsd.org/cgi/man.cgi?lpr"
	     name="lpr">, which submits the job to
	    the LPD spooler.  Because we used the <tt/-t/ option to
	    
	    <htmlurl url="http://www.freebsd.org/cgi/man.cgi?lpr"
	     name="lpr">, the spooler will convert the GNU troff output
	    into a format the default printer can understand when it
	    prints the job.

	<sect2><heading>Job Handling Options<label
	      id="printing:lpr:options:job-handling"></heading>

	  <p> The following options to 
	  <htmlurl url="http://www.freebsd.org/cgi/man.cgi?lpr"
	   name="lpr"> tell LPD to handle the
	    job specially:

	    <descrip>
	      <tag/-&num; <it/copies//

		Produce a number of <it/copies/ of each file in the
		job instead of just one copy.  An administrator may
		disable this option to reduce printer wear-and-tear
		and encourage photocopier usage.  See section <ref
		id="printing:advanced:restricting:copies"
		name="Restricting Multiple Copies">.

		<p> This example prints three copies of <tt/parser.c/
		followed by three copies of <tt/parser.h/ to the
		default printer:
<tscreen><verb>
lpr -#3 parser.c parser.h
</verb></tscreen>

	      <tag/-m/
	      
		Send mail after completing the print job.  With this
		option, the LPD system will send mail to your account
		when it finishes handling your job.  In its message,
		it will tell you if the job completed successfully or
		if there was an error, and (often) what the error was.

	      <tag/-s/ Do not copy the files to the spooling directory,
		but make symbolic links to them instead.

		If you are printing a large job, you probably want to
		use this option.  It saves space in the spooling
		directory (your job might overflow the free space on
		the filesystem where the spooling directory resides).
		It saves time as well since LPD will not have to copy
		each and every byte of your job to the spooling
		directory.

		There is a drawback, though: since LPD will refer to
		the original files directly, you cannot modify or
		remove them until they have been printed.

		<em/Note:/ If you are printing to a remote printer, LPD
		will eventually have to copy files from the local host
		to the remote host, so the <tt/-s/ option will save
		space only on the local spooling directory, not the
		remote.  It is still useful, though.

	      <tag/-r/

		Remove the files in the job after copying them to the
		spooling directory, or after printing them with the
		<tt/-s/ option.  Be careful with this option!

	    </descrip>

	<sect2><heading>Header Page Options<label
	      id="printing:lpr:options:misc"></heading>

	  <p> These options to 
	  <htmlurl url="http://www.freebsd.org/cgi/man.cgi?lpr"
	   name="lpr"> adjust the text that normally
	    appears on a job's header page.  If header pages are
	    suppressed for the destination printer, these options have
	    no effect.  See section <ref name="Header Pages"
	    id="printing:advanced:header-pages"> for information about
	    setting up header pages.

	    <descrip>
	      <tag/-C <it/text//

		Replace the hostname on the header page with
		<it/text/.  The hostname is normally the name of the
		host from which the job was submitted.

	      <tag/-J <it/text//

		Replace the job name on the header page with
		<it/text/.  The job name is normally the name of the
		first file of the job, or ``stdin'' if you are printing
		standard input.

	      <tag/-h/
	      
		Do not print any header page.  <em/Note:/ At some
		sites, this option may have no effect due to the way
		header pages are generated.  See <ref name="Header
		Pages" id="printing:advanced:header-pages"> for
		details.

	    </descrip>

      <sect1><heading>Administrating Printers<label
	    id="printing:lpc"></heading>

	<p> As an administrator for your printers, you have had to
	  install, set up, and test them.  Using the 
	  <htmlurl url="http://www.freebsd.org/cgi/man.cgi?lpc"
	   name="lpc"> command,
	  you can interact with your printers in yet more ways.  With
	  
	  <htmlurl url="http://www.freebsd.org/cgi/man.cgi?lpc"
	   name="lpc">, you can

	  <itemize>
	    <item>Start and stop the printers

	    <item>Enable and disable their queues

	    <item>Rearrange the order of the jobs in each queue.
	  </itemize>

	  First, a note about terminology: if a printer is
	  <em/stopped/, it will not print anything in its queue.  Users
	  can still submit jobs, which will wait in the queue until
	  the printer is <em/started/ or the queue is cleared.

	  If a queue is <em/disabled/, no user (except root) can
	  submit jobs for the printer.  An <em/enabled/ queue allows
	  jobs to be submitted.  A printer can be <em/started/ for a
	  disabled queue, in which case it will continue to print jobs
	  in the queue until the queue is empty.

	  In general, you have to have root privileges to use the
	  
	  <htmlurl url="http://www.freebsd.org/cgi/man.cgi?lpc"
	   name="lpc"> command.  Ordinary users can use the 
	   <htmlurl url="http://www.freebsd.org/cgi/man.cgi?lpc"
	    name="lpc">
	    command to get printer status and to restart a hung printer
	  only.

	  Here is a summary of the 
	  <htmlurl url="http://www.freebsd.org/cgi/man.cgi?lpc"
	   name="lpc"> commands.  Most of the
	  commands takes a <it/printer-name/ argument to tell on which
	  printer to operate.  You can use <tt/all/ for the
	  <it/printer-name/ to mean all printers listed in
	  <tt>/etc/printcap</tt>.

	  <descrip>
	    <tag/<tt/abort <it/printer-name///

	      Cancel the current job and stop the printer.  Users can
	      still submit jobs if the queue's enabled.

	    <tag/<tt/clean <it/printer-name///

	      Remove old files from the printer's spooling directory.
	      Occasionally, the files that make up a job are not
	      properly removed by LPD, particularly if there have been
	      errors during printing or a lot of administrative
	      activity.  This command finds files that do not belong in
	      the spooling directory and removes them.

	    <tag/<tt/disable <it/printer-name///

	      Disable queuing of new jobs.  If the printer's started,
	      it will continue to print any jobs remaining in the
	      queue.  The superuser (root) can always submit jobs,
	      even to a disabled queue.

	      This command is useful while you are testing a new
	      printer or filter installation: disable the queue and
	      submit jobs as root.  Other users will not be able to
	      submit jobs until you complete your testing and re-enable
	      the queue with the <tt/enable/ command.

	    <tag/<tt/down <it/printer-name/ <it/message...///

	      Take a printer down.  Equivalent to <tt/disable/
	      followed by <tt/stop/.  The <it/message/ appears as the
	      printer's status whenever a user checks the printer's
	      queue with 
	      <htmlurl url="http://www.freebsd.org/cgi/man.cgi?lpq"
	       name="lpq"> or status with <tt/lpc status/.

	    <tag/<tt/enable <it/printer-name///

	      Enable the queue for a printer.  Users can submit jobs
	      but the printer will not print anything until it is started.

	    <tag/<tt/help <it/command-name///

	      Print help on the command <it/command-name/.  With no
	      <it/command-name/, print a summary of the commands
	      available.

	    <tag/<tt/restart <it/printer-name///

	      Start the printer.  Ordinary users can use this command
	      if some extraordinary circumstance hangs LPD, but they
	      cannot start a printer stopped with either the <tt/stop/
	      or <tt/down/ commands.  The <tt/restart/ command is
	      equivalent to <tt/abort/ followed by <tt/start/.

	    <tag/<tt/start <it/printer-name///

	      Start the printer.  The printer will print jobs in its
	      queue.

	    <tag/<tt/stop <it/printer-name///

	      Stop the printer.  The printer will finish the current
	      job and will not print anything else in its queue.  Even
	      though the printer is stopped, users can still submit
	      jobs to an enabled queue.

	    <tag/<tt/topq <it/printer-name/ <it/job-or-username...///

	      Rearrange the queue for <it/printer-name/ by placing the
	      jobs with the listed <it/job/ numbers or the jobs
	      belonging to <it/username/ at the top of the queue.  For
	      this command, you cannot use <tt/all/ as the
	      <it/printer-name/.

	    <tag/<tt/up <it/printer-name///

	      Bring a printer up; the opposite of the <tt/down/
	      command.  Equivalent to <tt/start/ followed by
	      <tt/enable/.

	  </descrip>

	  
	  <htmlurl url="http://www.freebsd.org/cgi/man.cgi?lpc"
	   name="lpc"> accepts the above commands on the command line.  If
	  you do not enter any commands, 
	  <htmlurl url="http://www.freebsd.org/cgi/man.cgi?lpc"
	   name="lpc"> enters an interactive
	  mode, where you can enter commands until you type <tt/exit/,
	  <tt/quit/, or end-of-file.

    <sect><heading>Advanced Printer Setup<label
	  id="printing:advanced"></heading>

      <p> This section describes filters for printing specially
	formatted files, header pages, printing across networks, and
	restricting and accounting for printer usage.

	<sect1><heading>Filters<label
	    id="printing:advanced:filter-intro"></heading>

	<p> Although LPD handles network protocols, queuing, access
	  control, and other aspects of printing, most of the
	  <em/real/ work happens in the <em/filters/.  Filters are
	  programs that communicate with the printer and handle its
	  device dependencies and special requirements.  In the simple
	  printer setup, we installed a plain text filter---an
	  extremely simple one that should work with most printers
	  (section <ref id="printing:textfilter" name="Installing the
	  Text Filter">).

	  However, in order to take advantage of format conversion,
	  printer accounting, specific printer quirks, and so on, you
	  should understand how filters work.  It will ultimately be
	  the filter's responsibility to handle these aspects.  And the
	  bad news is that most of the time <em/you/ have to provide
	  filters yourself.  The good news is that many are generally
	  available; when they are not, they are usually easy to write.

	  Also, FreeBSD comes with one, <tt>/usr/libexec/lpr/lpf</tt>,
	  that works with many printers that can print plain text.
	  (It handles backspacing and tabs in the file, and does
	  accounting, but that is about all it does.)  There are also
	  several filters and filter components in the FreeBSD ports
	  collection.

	  Here is what you will find in this section:

	  <itemize>
	    <item>Section <ref id="printing:advanced:filters"
	      name="How Filters Work">, tries to give an overview of a
	      filter's role in the printing process.  You should read
	      this section to get an understanding of what is happening
	      ``under the hood'' when LPD uses filters.  This
	      knowledge could help you anticipate and debug problems
	      you might encounter as you install more and more filters
	      on each of your printers.
	      
	    <item>LPD expects every printer to be able to print plain
	      text by default.  This presents a problem for PostScript
	      (or other language-based printers) which cannot directly
	      print plain text.  Section <ref
	      id="printing:advanced:if-conversion" name="Accommodating
	      Plain Text Jobs on PostScript Printers"> tells you what
	      you should do to overcome this problem.  I recommend
	      reading this section if you have a PostScript printer.

	    <item>PostScript is a popular output format for many
	      programs.  Even some people (myself included) write
	      PostScript code directly.  But PostScript printers are
	      expensive.  Section <ref id="printing:advanced:ps"
	      name="Simulating PostScript on Non-PostScript Printers">
	      tells how you can further modify a printer's text filter
	      to accept and print PostScript data on a
	      <em/non-PostScript/ printer.  I recommend reading this
	      section if you do not have a PostScript printer.
	      
	    <item>Section <ref id="printing:advanced:convfilters"
		name="Conversion Filters"> tells about a way you can
		automate the conversion of specific file formats, such
		as graphic or typesetting data, into formats your
		printer can understand.  After reading this section,
		you should be able to set up your printers such that
		users can type <tt/lpr -t/ to print troff data, or
		<tt/lpr -d/ to print TeX DVI data, or <tt/lpr -v/ to
		print raster image data, and so forth.  I recommend
		reading this section.

	    <item>Section <ref id="printing:advanced:of" name="Output
		Filters"> tells all about a not often used feature of
		LPD: output filters.  Unless you are printing header
		pages (see <ref id="printing:advanced:header-pages"
		name="Header Pages">), you can probably skip that
		section altogether.

	    <item>Section <ref id="printing:advanced:lpf" name="lpf:
		a Text Filter"> describes <tt/lpf/, a fairly complete
		if simple text filter for line printers (and laser
		printers that act like line printers) that comes with
		FreeBSD.  If you need a quick way to get printer
		accounting working for plain text, or if you have a
		printer which emits smoke when it sees backspace
		characters, you should definitely consider <tt/lpf/.
	  </itemize>

	<sect2><heading>How Filters Work<label
	      id="printing:advanced:filters"></heading>

	  <p> As mentioned before, a filter is an executable program
	    started by LPD to handle the device-dependent part of
	    communicating with the printer.

	    When LPD wants to print a file in a job, it starts a
	    filter program.  It sets the filter's standard input to
	    the file to print, its standard output to the printer, and
	    its standard error to the error logging file (specified in
	    the <tt/lf/ capability in <tt>/etc/printcap</tt>, or
	    <tt>/dev/console</tt> by default).

	    Which filter LPD starts and the filter's arguments depend
	    on what is listed in the <tt>/etc/printcap</tt> file and
	    what arguments the user specified for the job on the
	    
	    <htmlurl url="http://www.freebsd.org/cgi/man.cgi?lpr"
	     name="lpr"> command line.  For example, if the user typed
	    <tt/lpr -t/, LPD would start the troff filter, listed in
	    the <tt/tf/ capability for the destination printer.  If
	    the user wanted to print plain text, it would start the
	    <tt/if/ filter (this is mostly true: see <ref
	    id="printing:advanced:of" name="Output Filters"> for
	    details).

	    There are three kinds of filters you can specify in
	    <tt>/etc/printcap</tt>:
	    <itemize>
	      <item>The <em/text filter/, confusingly called the
		<em/input filter/ in LPD documentation, handles
		regular text printing.  Think of it as the default
                filter.  LPD expects every printer to be able to print
		plain text by default, and it is the text filter's job
		to make sure backspaces, tabs, or other special
		characters do not confuse the printer.

		If you are in an environment where you have to account
		for printer usage, the text filter must also account
		for pages printed, usually by counting the number of
		lines printed and comparing that to the number of
		lines per page the printer supports.

		The text filter is started with the following argument
		list:
<tscreen>
<tt>[-c] -w<it/width/ -l<it/length/ -i<it/indent/ -n <it/login/ -h <it/host/ <it/acct-file/</tt>
</tscreen>
		where
		<descrip>
		  <tag/<tt/-c//

		    appears if the job's submitted with <tt/lpr -l/

		  <tag/<tt/<it/width///

		    is the value from the <tt/pw/ (page width)
		    capability specified in <tt>/etc/printcap</tt>,
		    default 132

		  <tag/<tt/<it/length///

		    is the value from the <tt/pl/ (page length)
		    capability, default 66

		  <tag/<tt/<it/indent///

		    is the amount of the indentation from <tt/lpr -i/,
		    default 0

		  <tag/<tt/<it/login///

		    is the account name of the user printing the file

		  <tag/<tt/<it/host///

		    is the host name from which the job was submitted

		  <tag/<tt/<it/acct-file///

		    is the name of the accounting file from the <tt/af/
		    capability.

		</descrip>

	      <item>A <em/conversion filter/ converts a specific file
		format into one the printer can render onto paper.
		For example, ditroff typesetting data cannot be
		directly printed, but you can install a conversion
		filter for ditroff files to convert the ditroff data
		into a form the printer can digest and print.  Section
		<ref id="printing:advanced:convfilters"
		name="Conversion Filters"> tells all about them.
		Conversion filters also need to do accounting, if you
		need printer accounting.

		Conversion filters are started with the following
		arguments:
<tscreen>
<tt>-x<it/pixel-width/ -y<it/pixel-height/ -n <it/login/ -h <it/host/ <it/acct-file/</tt>
</tscreen>
		where <it/pixel-width/ is the value from the <tt/px/
		capability (default 0) and <it/pixel-height/ is the
		value from the <tt/py/ capability (default 0).

	      <item>The <em/output filter/ is used only if there is no
		text filter, or if header pages are enabled.  In my
		experience, output filters are rarely used.  Section
		<ref id="printing:advanced:of" name="Output Filters">
		describe them.  There are only two arguments to an
		output filter:
<tscreen>
<tt>-w<it/width/ -l<it/length/</tt>
</tscreen>
                which are identical to the text filters <tt/-w/ and
		<tt/-l/ arguments.
	    </itemize>

	    Filters should also <em/exit/ with the following exit
	    status:
	    <descrip>
	      <tag/exit 0/

		If the filter printed the file successfully.

	      <tag/exit 1/

	        If the filter failed to print the file but wants LPD
		to try to print the file again.  LPD will restart a
		filter if it exits with this status.

	      <tag/exit 2/

	        If the filter failed to print the file and does not
		want LPD to try again.  LPD will throw out the file.
	    </descrip>

	    The text filter that comes with the FreeBSD release,
	    <tt>/usr/libexec/lpr/lpf</tt>, takes advantage of the page
	    width and length arguments to determine when to send a
	    form feed and how to account for printer usage.  It uses
	    the login, host, and accounting file arguments to make the
	    accounting entries.

	    If you are shopping for filters, see if they are
	    LPD-compatible.  If they are, they must support the
	    argument lists described above.  If you plan on writing
	    filters for general use, then have them support the same
	    argument lists and exit codes.

	<sect2><heading>Accommodating Plain Text Jobs on PostScript Printers
	    <label id="printing:advanced:if-conversion"></heading>

	  <p> If you are the only user of your computer and PostScript
	    (or other language-based) printer, and you promise to
	    never send plain text to your printer and to never use
	    features of various programs that will want to send plain
	    text to your printer, then you do not need to worry about
	    this section at all.

	    But, if you would like to send both PostScript and plain
	    text jobs to the printer, then you are urged to augment
	    your printer setup.  To do so, we have the text filter
	    detect if the arriving job is plain text or PostScript.
	    All PostScript jobs must start with <tt/&percnt;!/ (for
	    other printer languages, see your printer documentation).
	    If those are the first two characters in the job, we have
	    PostScript, and can pass the rest of the job directly.  If
	    those are not the first two characters in the file, then
	    the filter will convert the text into PostScript and print
	    the result.

	    How do we do this?

	    If you have got a serial printer, a great way to do it is to
	    install <tt/lprps/.  <tt/lprps/ is a PostScript printer
	    filter which performs two-way communication with the
	    printer.  It updates the printer's status file with
	    verbose information from the printer, so users and
	    administrators can see exactly what the state of the
	    printer is (such as ``toner low'' or ``paper jam'').  But
	    more importantly, it includes a program called <tt/psif/
	    which detects whether the incoming job is plain text and
	    calls <tt/textps/ (another program that comes with
	    <tt/lprps/) to convert it to PostScript.  It then uses
	    <tt/lprps/ to send the job to the printer.

	    <tt/lprps/ is part of the FreeBSD ports collection
	    (see <ref id="ports" name="The Ports Collection">).
	    You can fetch, build and install it
	    yourself, of course.  After installing <tt/lprps/, just
	    specify the pathname to the <tt/psif/ program that is part
	    of <tt/lprps/.  If you installed <tt/lprps/ from the ports
	    collection, use the following in the serial PostScript
	    printer's entry in <tt>/etc/printcap</tt>:
<tscreen><verb>
	    :if=/usr/local/libexec/psif:
</verb></tscreen>
	    You should also specify the <tt/rw/ capability; that tells
	    LPD to open the printer in read-write mode.

	    If you have a parallel PostScript printer (and therefore
	    cannot use two-way communication with the printer, which
	    <tt/lprps/ needs), you can use the following shell script
	    as the text filter:
<code>
#!/bin/sh
#
#  psif - Print PostScript or plain text on a PostScript printer
#  Script version; NOT the version that comes with lprps
#  Installed in /usr/local/libexec/psif
#

read first_line
first_two_chars=`expr "$first_line" : '\(..\)'`

if [ "$first_two_chars" = "%!" ]; then
   #
   #  PostScript job, print it.
   #
   echo $first_line &amp;&amp; cat &amp;&amp; printf "\004" &amp;&amp; exit 0
   exit 2
else
   #
   #  Plain text, convert it, then print it.
   #
   ( echo $first_line; cat ) | /usr/local/bin/textps &amp;&amp; printf "\004" &amp;&amp; exit 0
   exit 2
fi
</code>
	    In the above script, <tt/textps/ is a program we installed
	    separately to convert plain text to PostScript.  You can
	    use any text-to-PostScript program you wish.  The FreeBSD
	    ports collection (see <ref id="ports" name="The Ports
	    Collection">) includes a full featured text-to-PostScript
	    program called 
	    <htmlurl url="http://www.freebsd.org/cgi/man.cgi?manpath=FreeBSD+Ports&amp;query=a2ps"
	     name="a2ps"> that you might want to
	    investigate.

	<sect2><heading>Simulating PostScript on Non-PostScript Printers
	    <label id="printing:advanced:ps"></heading>

	  <p> PostScript is the <it/de facto/ standard for high
	    quality typesetting and printing.  PostScript is, however,
	    an <em/expensive/ standard.  Thankfully, Alladin
	    Enterprises has a free PostScript work-alike called
	    <it/Ghostscript/ that runs with FreeBSD.  Ghostscript can
	    read most PostScript files and can render their pages onto
	    a variety of devices, including many brands of
	    non-PostScript printers.  By installing Ghostscript and
	    using a special text filter for your printer, you can make
	    your non-PostScript printer act like a real PostScript
	    printer.

	    Ghostscript should be in the FreeBSD ports collection, if
	    you would like to install it from there.  You can fetch,
	    build, and install it quite easily yourself, as well.

	    To simulate PostScript, we have the text filter detect if
	    it is printing a PostScript file.  If it is not, then the
	    filter will pass the file directly to the printer;
	    otherwise, it will use Ghostscript to first convert the
	    file into a format the printer will understand.

	    Here is an example: the following script is a text filter
	    for Hewlett Packard DeskJet 500 printers.  For other
	    printers, substitute the <tt/-sDEVICE/ argument to the
	    
	    <htmlurl url="http://www.freebsd.org/cgi/man.cgi?manpath=FreeBSD+Ports&amp;query=gs"
	     name="gs"> (Ghostscript) command.  (Type <tt/gs -h/ to get a
	    list of devices the current installation of Ghostscript
	    supports.)
<code>
#!/bin/sh
#
#  ifhp - Print Ghostscript-simulated PostScript on a DeskJet 500
#  Installed in /usr/local/libexec/hpif

#
#  Treat LF as CR+LF:
#
printf "\033&amp;k2G" || exit 2

#
#  Read first two characters of the file
#
read first_line
first_two_chars=`expr "$first_line" : '\(..\)'`

if [ "$first_two_chars" = "%!" ]; then
    #
    #  It is PostScript; use Ghostscript to scan-convert and print it
    #
    /usr/local/bin/gs -dSAFER -dNOPAUSE -q -sDEVICE=djet500 -sOutputFile=- - \
        &amp;&amp; exit 0

else
    #
    #  Plain text or HP/PCL, so just print it directly; print a form
    #  at the end to eject the last page.
    #
    echo $first_line &amp;&amp; cat &amp;&amp; printf "\f" &amp;&amp; exit 0
fi

exit 2
</code>
	    Finally, you need to notify LPD of the filter via the
	    <tt/if/ capability:
<tscreen><verb>
	:if=/usr/local/libexec/hpif:
</verb></tscreen>
	    That is it.  You can type <tt/lpr plain.text/ and <tt/lpr
	    whatever.ps/ and both should print successfully.


	<sect2><heading>Conversion Filters<label
	      id="printing:advanced:convfilters"></heading>

	  <p> After completing the simple setup described in <ref
	      name="Simple Printer Setup" id="printing:simple">, the
	      first thing you will probably want to do is install
	      conversion filters for your favorite file formats
	      (besides plain ASCII text).

	    <sect3><heading>Why Install Conversion Filters?</heading>

	    <p> Conversion filters make printing various kinds of
	      files easy.  As an example, suppose we do a lot of work
	      with the TeX typesetting system, and we have a
	      PostScript printer.  Every time we generate a DVI file
	      from TeX, we cannot print it directly until we convert
	      the DVI file into PostScript.  The command sequence
	      goes like this:
<tscreen><verb>
dvips seaweed-analysis.dvi
lpr seaweed-analysis.ps
</verb></tscreen>
	      By installing a conversion filter for DVI files, we can
	      skip the hand conversion step each time by having LPD do
	      it for us.  Now, each time we get a DVI file, we are just
	      one step away from printing it:
<tscreen><verb>
lpr -d seaweed-analysis.dvi
</verb></tscreen>
	      We got LPD to do the DVI file conversion for us by
	      specifying the <tt/-d/ option.  Section <ref
		id="printing:lpr:options:format" name="Formatting and
		Conversion Options"> lists the conversion options.

	      For each of the conversion options you want a printer to
	      support, install a <em/conversion filter/ and specify
	      its pathname in <tt>/etc/printcap</tt>.  A conversion
	      filter is like the text filter for the simple printer
	      setup (see section <ref id="printing:textfilter"
	      name="Installing the Text Filter">) except that instead
	      of printing plain text, the filter converts the file
	      into a format the printer can understand.

	  <sect3><heading>Which Conversions Filters Should I Install?
	    </heading>

	    <p> You should install the conversion filters you expect
	      to use.  If you print a lot of DVI data, then a DVI
	      conversion filter is in order.  If you have got plenty of
	      troff to print out, then you probably want a troff
	      filter.

	      The following table summarizes the filters that LPD
	      works with, their capability entries for the
	      <tt>/etc/printcap</tt> file, and how to invoke them with
	      the <tt/lpr/ command:
<code>
              /etc/printcap
File type       Capability  lpr option
------------  ------------- ----------
cifplot            cf          -c
DVI                df          -d
plot               gf          -g
ditroff            nf          -n
FORTRAN text       rf          -f
troff              tf          -t
raster             vf          -v
plain text         if     none, -p, or -l
</code>

	      In our example, using <tt/lpr -d/ means the printer
	      needs a <tt/df/ capability in its entry in
	      <tt>/etc/printcap</tt>.

	      Despite what others might contend, formats like FORTRAN
	      text and plot are probably obsolete.  At your site, you
	      can give new meanings to these or any of the formatting
	      options just by installing custom filters.  For example,
	      suppose you would like to directly print Printerleaf files
	      (files from the Interleaf desktop publishing program),
	      but will never print plot files.  You could install a
	      Printerleaf conversion filter under the <tt/gf/
	      capability and then educate your users that <tt/lpr -g/
	      mean ``print Printerleaf files.''

	  <sect3><heading>Installing Conversion Filters</heading>

	    <p> Since conversion filters are programs you install
	      outside of the base FreeBSD installation, they should
	      probably go under <tt>/usr/local</tt>.  The directory
	      <tt>/usr/local/libexec</tt> is a popular location, since
	      they are specialized programs that only LPD will
	      run; regular users should not ever need to run them.

	      To enable a conversion filter, specify its pathname
	      under the appropriate capability for the destination
	      printer in <tt>/etc/printcap</tt>.

	      In our example, we will add the DVI conversion filter to
	      the entry for the printer named <tt/bamboo/.  Here is the
	      example <tt>/etc/printcap</tt> file again, with the new
	      <tt/df/ capability for the printer <tt/bamboo/
<code>
#
#  /etc/printcap for host rose - added df filter for bamboo
#
rattan|line|diablo|lp|Diablo 630 Line Printer:\
	:sh:sd=/var/spool/lpd/rattan:\
	:lp=/dev/lpt0:\
	:if=/usr/local/libexec/if-simple:

bamboo|ps|PS|S|panasonic|Panasonic KX-P4455 PostScript v51.4:\
	:sh:sd=/var/spool/lpd/bamboo:\
	:lp=/dev/ttyd5:fs#0x82000e1:xs#0x820:rw:\
	:if=/usr/local/libexec/psif:\
	:df=/usr/local/libexec/psdf:
</code>
	      The DVI filter is a shell script named
	      <tt>/usr/local/libexec/psdf</tt>.  Here is that script:
<code>
#!bin/sh
#
#  psdf - DVI to PostScript printer filter
#  Installed in /usr/local/libexec/psdf
#
#  Invoked by lpd when user runs lpr -d
#
exec /usr/local/bin/dvips -f | /usr/local/libexec/lprps "$@"
</code>
	      This script runs 
	      <htmlurl url="http://www.freebsd.org/cgi/man.cgi?manpath=FreeBSD+Ports&amp;query=dvips"
	       name="dvips"> in filter mode (the <tt/-f/
	      argument) on standard input, which is the job to print.
	      It then starts the PostScript printer filter <tt/lprps/
	      (see section <ref id="printing:advanced:if-conversion"
	      name="Accommodating Plain Text Jobs on PostScript
	      Printers">) with the arguments LPD passed to this script.
	      <tt/lprps/ will use those arguments to account for the
	      pages printed.

	  <sect3><heading>More Conversion Filter Examples</heading>

	    <p> Since there is no fixed set of steps to install
	      conversion filters, let me instead provide more
	      examples.  Use these as guidance to making your own
	      filters.  Use them directly, if appropriate.

	      This example script is a raster (well, GIF file,
	      actually) conversion filter for a Hewlett Packard
	      LaserJet III-Si printer:
<code>
#!/bin/sh
#
#  hpvf - Convert GIF files into HP/PCL, then print
#  Installed in /usr/local/libexec/hpvf

PATH=/usr/X11R6/bin:$PATH; export PATH

giftopnm | ppmtopgm | pgmtopbm | pbmtolj -resolution 300 \
    && exit 0 \
    || exit 2
</code>
	      It works by converting the GIF file into a portable
	      anymap, converting that into a portable graymap,
	      converting that into a portable bitmap, and converting
	      that into LaserJet/PCL-compatible data.

	      Here is the <tt>/etc/printcap</tt> file with an entry for
	      a printer using the above filter:
<code>
#
#  /etc/printcap for host orchid
#
teak|hp|laserjet|Hewlett Packard LaserJet 3Si:\
	:lp=/dev/lpt0:sh:sd=/var/spool/lpd/teak:mx#0:\
	:if=/usr/local/libexec/hpif:\
	:vf=/usr/local/libexec/hpvf:
</code>

	      The following script is a conversion filter for troff
	      data from the groff typesetting system for the
	      PostScript printer named <tt/bamboo/:
<code>
#!/bin/sh
#
#  pstf - Convert groff's troff data into PS, then print.
#  Installed in /usr/local/libexec/pstf
#
exec grops | /usr/local/libexec/lprps "$@"
</code>
	      The above script makes use of <tt/lprps/ again to handle
	      the communication with the printer.  If the printer were
	      on a parallel port, we would use this script instead:
<code>
#!/bin/sh
#
#  pstf - Convert groff's troff data into PS, then print.
#  Installed in /usr/local/libexec/pstf
#
exec grops
</code>
	      That is it.  Here is the entry we need to add to
	      <tt>/etc/printcap</tt> to enable the filter:
<tscreen><verb>
	:tf=/usr/local/libexec/pstf:
</verb></tscreen>

              Here is an example that might make old hands at FORTRAN
              blush.  It is a FORTRAN-text filter for any printer that
	      can directly print plain text.  We will install it for the
	      printer <tt/teak/:
<code>
#!/bin/sh
#
# hprf - FORTRAN text filter for LaserJet 3si:
# Installed in /usr/local/libexec/hprf
#

printf "\033&amp;k2G" &amp;&amp; fpr &amp;&amp; printf "\f" &amp;&amp; exit 0
exit 2
</code>
	      And we will add this line to the <tt>/etc/printcap</tt>
	      for the printer <tt/teak/ to enable this filter:
<tscreen><verb>
	:rf=/usr/local/libexec/hprf:
</verb></tscreen>

	      Here is one final, somewhat complex example.  We will add a
	      DVI filter to the LaserJet printer <tt/teak/ introduced
	      earlier.  First, the easy part: updating
	      <tt>/etc/printcap</tt> with the location of the DVI
	      filter:
<tscreen><verb>
	:df=/usr/local/libexec/hpdf:
</verb></tscreen>

	      Now, for the hard part: making the filter.  For that, we
	      need a DVI-to-LaserJet/PCL conversion program.  The
	      FreeBSD ports collection (see <ref id="ports" name="The
	      Ports Collection">) has one: 
	      <htmlurl url="http://www.freebsd.org/cgi/man.cgi?manpath=FreeBSD+Ports&amp;query=dvi2xx"
	       name="dvi2xx"> is the name of
	      the package.  Installing this package gives us the
	      program we need, 
	      <htmlurl url="http://www.freebsd.org/cgi/man.cgi?manpath=FreeBSD+Ports&amp;query=dvilj2p"
	       name="dvilj2p">, which converts DVI into
	      LaserJet IIp, LaserJet III, and LaserJet 2000 compatible
	      codes.

	      
	      <htmlurl url="http://www.freebsd.org/cgi/man.cgi?manpath=FreeBSD+Ports&amp;query=dvilj2p"
	       name="dvilj2p"> makes the filter <tt/hpdf/ quite complex
	      since 
	      <htmlurl url="http://www.freebsd.org/cgi/man.cgi?manpath=FreeBSD+Ports&amp;query=dvilj2p"
	       name="dvilj2p"> cannot read from standard input.  It
	      wants to work with a filename.  What is worse, the
	      filename has to end in <tt/.dvi/ so using
	      <tt>/dev/fd/0</tt> for standard input is problematic.
	      We can get around that problem by linking (symbolically)
	      a temporary file name (one that ends in <tt/.dvi/) to
	      <tt>/dev/fd/0</tt>, thereby forcing 
	      <htmlurl url="http://www.freebsd.org/cgi/man.cgi?manpath=FreeBSD+Ports&amp;query=dvilj2p"
	       name="dvilj2p"> to read
	      from standard input.

	      The only other fly in the ointment is the fact that we
	      cannot use /tmp for the temporary link.  Symbolic links
	      are owned by user and group <tt/bin/.  The filter runs
	      as user <tt/daemon/.  And the <tt>/tmp</tt> directory
	      has the sticky bit set.  The filter can create the link,
	      but it will not be able clean up when done and remove it
	      since the link will belong to a different user.

	      Instead, the filter will make the symbolic link in the
	      current working directory, which is the spooling
	      directory (specified by the <tt/sd/ capability in
	      <tt>/etc/printcap</tt>).  This is a perfect place for
	      filters to do their work, especially since there is
	      (sometimes) more free disk space in the spooling directory
	      than under <tt>/tmp</tt>.

	      Here, finally, is the filter:
<code>
#!/bin/sh
#
#  hpdf - Print DVI data on HP/PCL printer
#  Installed in /usr/local/libexec/hpdf

PATH=/usr/local/bin:$PATH; export PATH

#
#  Define a function to clean up our temporary files.  These exist
#  in the current directory, which will be the spooling directory
#  for the printer.
#
cleanup() {
   rm -f hpdf$$.dvi
}

#
#  Define a function to handle fatal errors: print the given message
#  and exit 2.  Exiting with 2 tells LPD to do not try to reprint the
#  job.
#
fatal() {
    echo "$@" 1>&amp;2
    cleanup
    exit 2
}

#
#  If user removes the job, LPD will send SIGINT, so trap SIGINT
#  (and a few other signals) to clean up after ourselves.
#
trap cleanup 1 2 15 

#
#  Make sure we are not colliding with any existing files.
#
cleanup

#
#  Link the DVI input file to standard input (the file to print).
#
ln -s /dev/fd/0 hpdf$$.dvi || fatal "Cannot symlink /dev/fd/0"

#
#  Make LF = CR+LF
#
printf "\033&amp;k2G" || fatal "Cannot initialize printer"

# 
#  Convert and print.  Return value from dvilj2p does not seem to be
#  reliable, so we ignore it.
#
dvilj2p -M1 -q -e- dfhp$$.dvi

#
#  Clean up and exit
#
cleanup
exit 0
</code>

	  <sect3><heading>Automated Conversion: An Alternative To Conversion Filters
	      <label id="printing:advanced:autoconv"></heading>

	    <p> All these conversion filters accomplish a lot for your
	      printing environment, but at the cost forcing the user
	      to specify (on the 
	      <htmlurl url="http://www.freebsd.org/cgi/man.cgi?lpr"
	       name="lpr"> command line) which one to
	      use.  If your users are not particularly computer
	      literate, having to specify a filter option will become
	      annoying.  What is worse, though, is that an incorrectly
	      specified filter option may run a filter on the wrong
	      type of file and cause your printer to spew out hundreds
	      of sheets of paper.

	      Rather than install conversion filters at all, you might
	      want to try having the text filter (since it is the
	      default filter) detect the type of file it has been asked to
	      print and then automatically run the right conversion
	      filter.  Tools such as <tt/file/ can be of help here.
	      Of course, it will be hard to determine the differences
	      between <em/some/ file types---and, of course, you can
	      still provide conversion filters just for them.

	      The FreeBSD ports collection has a text filter that
	      performs automatic conversion called 
	      <htmlurl url="http://www.freebsd.org/cgi/man.cgi?manpath=FreeBSD+Ports&amp;query=apsfilter"
	       name="apsfilter">. It
	      can detect plain text, PostScript, and DVI files, run
	      the proper conversions, and print.

	<sect2><heading>Output Filters<label
	      id="printing:advanced:of"></heading>
	  
	  <p> The LPD spooling system supports one other type of
	    filter that we have not yet explored: an output filter.  An
	    output filter is intended for printing plain text only,
	    like the text filter, but with many simplifications.  If
	    you are using an output filter but no text filter, then
	    <itemize>
	      <item>LPD starts an output filter once for the entire
		job instead of once for each file in the job.

	      <item>LPD does not make any provision to identify the
		start or the end of files within the job for the
		output filter.

	      <item>LPD does not pass the user's login or host to
		the filter, so it is not intended to do accounting.  In
		fact, it gets only two arguments:
<tscreen>
<tt>-w<it/width/ -l<it/length/</tt>
</tscreen>
		where <it/width/ is from the <tt/pw/ capability and
		<it/length/ is from the <tt/pl/ capability for the
		printer in question.
	    </itemize>

	    Do not be seduced by an output filter's simplicity.  If
	    you would like each file in a job to start on a different page
	    an output filter <em/will not work/.  Use a text filter (also
	    known as an input filter); see section <ref
	    id="printing:textfilter" name="Installing the Text
	    Filter">.  Furthermore, an output filter is actually
	    <em/more complex/ in that it has to examine the byte
	    stream being sent to it for special flag characters and
	    must send signals to itself on behalf of LPD.

	    However, an output filter is <em/necessary/ 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 <em/futile/ if you want to charge
	    header pages to the requesting user's account, since LPD
	    does not give any user or host information to the output
	    filter.)

	    On a single printer, LPD allows both an output filter and
	    text or other filters.  In such cases, LPD will start the
	    output filter to print the header page (see section <ref
	    id="printing:advanced:header-pages" name="Header Pages">)
	    only.  LPD then expects the output filter to <em/stop
	    itself/ 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 SIGSTOP to
	    itself.  When LPD's done running other filters, it will
	    restart the output filter by sending SIGCONT to it.

	    If there is an output filter but <em/no/ text filter and
	    LPD is working on a plain text job, LPD 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 <em/not/ what you want.  In almost all
	    cases, you need a text filter.

	    The program <tt/lpf/, 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/lpf/.  You
	    can also wrap <tt/lpf/ in a shell script to handle any
	    initialization codes the printer might require.

	<sect2><heading><tt/lpf/: a Text Filter<label
	      id="printing:advanced:lpf"></heading>

	  <p> The program <tt>/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/lpr
	    -i/), allow literal characters to pass (job submitted with
	    <tt/lpr -l/), adjust the printing position for backspaces
	    and tabs in the job, and account for pages printed.  It
	    can also act like an output filter.

	    <tt/lpf/ 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/lpf/.

	    In order for <tt/lpf/ to do page accounting correctly, it
	    needs correct values filled in for the <tt/pw/ and <tt/pl/
	    capabilities in the <tt>/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 <ref
	    id="printing:advanced:acct" name="Accounting for Printer
	    Usage">.

      <sect1><heading>Header Pages<label
	    id="printing:advanced:header-pages"></heading>

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

	  Header pages, also known as <em/banner/ or <em/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 <em/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 <ref
	  id="printing:advanced:header-pages:ps" name="Header Pages on
	  PostScript Printers">.

	<sect2><heading>Enabling Header Pages<label
	      id="printing:advanced:header-pages:enabling"></heading>

	  <p> In the <ref id="printing:simple" name="Simple Printer
	      Setup">, we turned off header pages by specifying
	    <tt/sh/ (meaning ``suppress header'') in the
	    <tt>/etc/printcap</tt> file.  To enable header pages for
	    a printer, just remove the <tt/sh/ capability.

	    Sounds too easy, right?

	    You are right.  You <em/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:
<code>
#!/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
</code>
	    Specify the path to the output filter in the <tt/of/
	    capability.  See <ref id="printing:advanced:of"
	    name="Output Filters"> for more information.

	    Here is an example <tt>/etc/printcap</tt> file for the printer
	    <tt/teak/ that we introduced earlier; we enabled header
	    pages and added the above output filter:
<code>
#
#  /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:
</code>
	    Now, when users print jobs to <tt/teak/, 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/lpr -h/; see <ref
	    id="printing:lpr:options:misc" name="Header Page Options">
	    for more 
	    <htmlurl url="http://www.freebsd.org/cgi/man.cgi?lpr"
	     name="lpr"> options.

	    <tt/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 <tt/ff/ capability in <tt>/etc/printcap</tt>.

	<sect2><heading>Controlling Header Pages<label
	      id="printing:advanced:header-pages:controlling"></heading>

	  <p> By enabling header pages, LPD will produce a <em/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):
<tscreen><verb>
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
</verb></tscreen>
	    LPD appends a form feed after this text so the job starts
	    on a new page (unless you have <tt/sf/ (suppress form
	    feeds) in the destination printer's entry in
	    <tt>/etc/printcap</tt>).

	    If you prefer, LPD can make a <em/short header/; specify
	    <tt/sb/ (short banner) in the <tt>/etc/printcap</tt> file.
	    The header page will look like this:
<tscreen><verb>
rose:kelly  Job: outline  Date: Sun Sep 17 11:07:51 1995
</verb></tscreen>
	    Also by default, LPD prints the header page first, then
	    the job.  To reverse that, specify <tt/hl/ (header last)
	    in <tt>/etc/printcap</tt>.

	<sect2><heading>Accounting for Header Pages<label
	      id="printing:advanced:header-pages:accounting"></heading>

	  <p> Using LPD's built-in header pages enforces a particular
	    paradigm when it comes to printer accounting: header pages
	    must be <em/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
	    <em/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
	    <tt/lpr -h/.  They could still be charged for header pages
	    they did not print.  Basically, <tt/lpr -h/ will be the
	    preferred option of environmentally-minded users, but you
	    cannot offer any incentive to use it.

	    It is <em/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 <tt/lpr -h/, they will
	    still get them and be charged for them since LPD does not
	    pass any knowledge of the <tt/-h/ option to any of the
	    filters.

	    So, what are your options?

	    You can
	    <itemize>
	      <item>Accept LPD's paradigm and make header pages free.

	      <item>Install an alternative to LPD, such as LPDng or
		PLP.  Section <ref name="Alternatives to the Standard
		Spooler" id="printing:lpd-alternatives"> tells more
		about other spooling software you can substitute for
		LPD.

	      <item>Write a <em/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 <tt/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 <tt/sh/ (short
		header) capability in <tt>/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.
	    </itemize>

	<sect2><heading>Header Pages on PostScript Printers<label
	      id="printing:advanced:header-pages:ps"></heading>

	  <p> 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 <tt/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:
<code>
#!/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>&amp;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
</code>
	    Now, each of the conversion filters and the text filter
	    can call this script to first generate the header page,
	    and then print the user's job.  Here is the DVI conversion
	    filter from earlier in this document, modified to make a
	    header page:
<code>
#!/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>&amp;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>&amp;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
</code>
	    Notice how the filter has to parse the argument list in
	    order to determine the user and host name.  The parsing
	    for the other conversion filters is identical.  The text
	    filter takes a slightly different set of arguments, though
	    (see section <ref id="printing:advanced:filters" name="How
	    Filters Work">).

	    As we have mentioned before, the above scheme, though fairly
	    simple, disables the ``suppress header page'' option (the
	    <tt/-h/ option) to <tt/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
	    <ref id="printing:advanced:header-pages:accounting"
	    name="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 <tt/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 <tt/lprps/, which comes with an output
	    filter, <tt/psof/, which does the above.  Note that
	    <tt/psof/ does not charge for header pages.

      <sect1><heading>Networked Printing<label
	    id="printing:advanced:network-printers"></heading>

	<p> FreeBSD supports networked printing: sending jobs to
	  remote printers.  Networked printing generally refers to two
	  different things:
	  <itemize>
	    <item>Accessing a printer attached to a remote host.  You
	      install a printer that has a conventional serial or
	      parallel interface on one host.  Then, you set up LPD to
	      enable access to the printer from other hosts on the
	      network.  Section <ref id="printing:advanced:network:rm"
	      name="Printers Installed on Remote Hosts"> tells how to
	      do this.

	      <item>Accessing a printer attached directly to a network.
		The printer has a network interface in addition (or in
		place of) a more conventional serial or parallel
		interface.  Such a printer might work as follows:

	      <itemize>
		<item>It might understand the LPD protocol and can
		  even queue jobs from remote hosts.  In this case, it
		  acts just like a regular host running LPD.  Follow
		  the same procedure in section <ref
		  id="printing:advanced:network:rm" name="Printers
		  Installed on Remote Hosts"> to set up such a
		  printer.

		<item>It might support a data stream network
		  connection.  In this case, you ``attach'' the
		  printer to one host on the network by making that
		  host responsible for spooling jobs and sending them
		  to the printer.  Section <ref
		  id="printing:advanced:network:net-if" name="Printers
		  with Networked Data Stream Interfaces"> gives some
		  suggestions on installing such printers.
	      </itemize>
	  </itemize>

	<sect2><heading>Printers Installed on Remote Hosts<label
	      id="printing:advanced:network:rm"></heading>

	  <p> The LPD spooling system has built-in support for sending
	    jobs to other hosts also running LPD (or are compatible
	    with LPD).  This feature enables you to install a printer
	    on one host and make it accessible from other hosts.  It
	    also works with printers that have network interfaces that
	    understand the LPD protocol.  

	    To enable this kind of remote printing, first install a
	    printer on one host, the <em/printer host/, using the
	    simple printer setup described in <ref
	    id="printing:simple" name="Simple Printer Setup">.  Do any
	    advanced setup in <ref id="printing:advanced"
	    name="Advanced Printer Setup"> that you need.  Make sure
	    to test the printer and see if it works with the features
	    of LPD you have enabled.

	    If you are using a printer with a network interface that is
	    compatible with LPD, then the <em/printer host/ in the
	    discussion below is the printer itself, and the
	    <em/printer name/ is the name you configured for the
	    printer.  See the documentation that accompanied your
	    printer and/or printer-network interface.

	    Then, on the other hosts you want to have access to the
	    printer, make an entry in their <tt>/etc/printcap</tt>
	    files with the following:
	    <enum>
	      <item>Name the entry anything you want.  For
		simplicity, though, you probably want to use the same
		name and aliases as on the printer host.

	      <item>Leave the <tt/lp/ capability blank, explicitly
		(<tt/:lp=:/).

	      <item>Make a spooling directory and specify its
		location in the <tt/sd/ capability.  LPD will store
		jobs here before they get sent to the printer host.

	      <item>Place the name of the printer host in the <tt/rm/
		capability.

	      <item>Place the printer name on the <em/printer host/ in
		the <tt/rp/ capability.
	    </enum>
	    That is it.  You do not need to list conversion filters,
	    page dimensions, or anything else in the
	    <tt>/etc/printcap</tt> file.

	    Here is an example.  The host rose has two printers,
	    <tt/bamboo/ and <tt/rattan/.  We will enable users on the
	    host orchid to print to those printers.  Here is the
	    <tt>/etc/printcap</tt> file for orchid (back from section
	    <ref id="printing:advanced:header-pages:enabling"
	    name="Enabling Header Pages">).  It already had the entry
	    for the printer <tt/teak/; we have added entries for the two
	    printers on the host rose:
<code>
#
#  /etc/printcap for host orchid - added (remote) printers on rose
#

#
#  teak is local; it is connected directly to orchid:
#
teak|hp|laserjet|Hewlett Packard LaserJet 3Si:\
	:lp=/dev/lpt0:sd=/var/spool/lpd/teak:mx#0:\
	:if=/usr/local/libexec/ifhp:\
	:vf=/usr/local/libexec/vfhp:\
	:of=/usr/local/libexec/ofhp:

#
#  rattan is connected to rose; send jobs for rattan to rose:
#
rattan|line|diablo|lp|Diablo 630 Line Printer:\
	:lp=:rm=rose:rp=rattan:sd=/var/spool/lpd/rattan:

#
#  bamboo is connected to rose as well:
#
bamboo|ps|PS|S|panasonic|Panasonic KX-P4455 PostScript v51.4:\
	:lp=:rm=rose:rp=bamboo:sd=/var/spool/lpd/bamboo:
</code>
	    Then, we just need to make spooling directories on orchid:
<tscreen><verb>
mkdir -p /var/spool/lpd/rattan /var/spool/lpd/bamboo
chmod 770 /var/spool/lpd/rattan /var/spool/lpd/bamboo
chown daemon.daemon /var/spool/lpd/rattan /var/spool/lpd/bamboo
</verb></tscreen>

	    Now, users on orchid can print to <tt/rattan/ and
	    <tt/bamboo/.  If, for example, a user on orchid typed
<tscreen><verb>
lpr -P bamboo -d sushi-review.dvi
</verb></tscreen>
	    the LPD system on orchid would copy the job to the
	    spooling directory <tt>/var/spool/lpd/bamboo</tt> and note
	    that it was a DVI job.  As soon as the host rose has room
	    in its <tt/bamboo/ spooling directory, the two
	    LPDs would transfer the file to rose.  The file would wait
	    in rose's queue until it was finally printed.  It would be
	    converted from DVI to PostScript (since bamboo is a
	    PostScript printer) on rose.

	<sect2><heading>Printers with Networked Data Stream Interfaces<label
	      id="printing:advanced:network:net-if"></heading>

	  <p> Often, when you buy a network interface card for a
	    printer, you can get two versions: one which emulates a
	    spooler (the more expensive version), or one which just
	    lets you send data to it as if you were using a serial or
	    parallel port (the cheaper version).  This section tells
	    how to use the cheaper version.  For the more expensive
	    one, see the previous section <ref name="Printers
	    Installed on Remote Hosts" id="printing:advanced:network:rm">.

	    The format of the <tt>/etc/printcap</tt> file lets you
	    specify what serial or parallel interface to use, and (if
	    you are using a serial interface), what baud rate, whether
	    to use flow control, delays for tabs, conversion of
	    newlines, and more.  But there is no way to specify a
	    connection to a printer that is listening on a TCP/IP or
	    other network port.

	    To send data to a networked printer, you need to develop a
	    communications program that can be called by the text and
	    conversion filters.  Here is one such example: the script
	    <tt/netprint/ takes all data on standard input and sends
	    it to a network-attached printer.  We specify the hostname
	    of the printer as the first argument and the port number
	    to which to connect as the second argument to
	    <tt/netprint/.  Note that this supports one-way
	    communication only (FreeBSD to printer); many network
	    printers support two-way communication, and you might want
	    to take advantage of that (to get printer status, perform
	    accounting, etc.).
<code>
#!/usr/bin/perl
#
#  netprint - Text filter for printer attached to network
#  Installed in /usr/local/libexec/netprint
#

$#ARGV eq 1 || die "Usage: $0 <printer-hostname> <port-number>";

$printer_host = $ARGV[0];
$printer_port = $ARGV[1];

require 'sys/socket.ph';

($ignore, $ignore, $protocol) = getprotobyname('tcp');
($ignore, $ignore, $ignore, $ignore, $address)
    = gethostbyname($printer_host);

$sockaddr = pack('S n a4 x8', &amp;AF_INET, $printer_port, $address);

socket(PRINTER, &amp;PF_INET, &amp;SOCK_STREAM, $protocol)
    || die "Can't create TCP/IP stream socket: $!";
connect(PRINTER, $sockaddr) || die "Can't contact $printer_host: $!";
while (<STDIN>) { print PRINTER; }
exit 0;
</code>
	    We can then use this script in various filters.  Suppose
	    we had a Diablo 750-N line printer connected to the
	    network.  The printer accepts data to print on port number
	    5100.  The host name of the printer is scrivener.  Here is
	    the text filter for the printer:
<code>
#!/bin/sh
#
#  diablo-if-net - Text filter for Diablo printer `scrivener' listening
#  on port 5100.  Installed in /usr/local/libexec/diablo-if-net
#

exec /usr/libexec/lpr/lpf "$@" | /usr/local/libexec/netprint scrivener 5100
</code>


      <sect1><heading>Restricting Printer Usage<label
	    id="printing:advanced:restricting"></heading>
	
	<p> This section gives information on restricting printer
	  usage.  The LPD system lets you control who can access a
	  printer, both locally or remotely, whether they can print
	  multiple copies, how large their jobs can be, and how large
	  the printer queues can get.

	<sect2><heading>Restricting Multiple Copies<label
	      id="printing:advanced:restricting:copies"></heading>

	  <p> The LPD system makes it easy for users to print multiple
	    copies of a file.  Users can print jobs with <tt/lpr -&num;5/
	    (for example) and get five copies of each file in the job.
	    Whether this is a good thing is up to you.

	    If you feel multiple copies cause unnecessary wear and
	    tear on your printers, you can disable the <tt/-&num;/ option
	    to 
	    <htmlurl url="http://www.freebsd.org/cgi/man.cgi?lpr"
	     name="lpr"> by adding the <tt/sc/ capability to the
	    <tt>/etc/printcap</tt> file.  When users submit jobs
	    with the <tt/-&num;/ option, they will see
<tscreen><verb>
lpr: multiple copies are not allowed
</verb></tscreen>

	    Note that if you have set up access to a printer remotely
	    (see section <ref name="Printers Installed on Remote
	    Hosts" id="printing:advanced:network:rm">), you need the
	    <tt/sc/ capability on the remote <tt>/etc/printcap</tt>
	    files as well, or else users will still be able to submit
	    multiple-copy jobs by using another host.

	    Here is an example.  This is the <tt>/etc/printcap</tt>
	    file for the host rose.  The printer <tt/rattan/ is quite
	    hearty, so we will allow multiple copies, but the laser
	    printer <tt/bamboo/'s a bit more delicate, so we will
	    disable multiple copies by adding the <tt/sc/ capability:
<code>
#
#  /etc/printcap for host rose - restrict multiple copies on bamboo
#
rattan|line|diablo|lp|Diablo 630 Line Printer:\
	:sh:sd=/var/spool/lpd/rattan:\
	:lp=/dev/lpt0:\
	:if=/usr/local/libexec/if-simple:

bamboo|ps|PS|S|panasonic|Panasonic KX-P4455 PostScript v51.4:\
	:sh:sd=/var/spool/lpd/bamboo:sc:\
	:lp=/dev/ttyd5:fs#0x82000e1:xs#0x820:rw:\
	:if=/usr/local/libexec/psif:\
	:df=/usr/local/libexec/psdf:
</code>
	    Now, we also need to add the <tt/sc/ capability on the
	    host orchid's <tt>/etc/printcap</tt> (and while we are at
	    it, let us disable multiple copies for the printer
	    <tt/teak/):
<code>
#
#  /etc/printcap for host orchid - no multiple copies for local
#  printer teak or remote printer bamboo

teak|hp|laserjet|Hewlett Packard LaserJet 3Si:\
	:lp=/dev/lpt0:sd=/var/spool/lpd/teak:mx#0:sc:\
	:if=/usr/local/libexec/ifhp:\
	:vf=/usr/local/libexec/vfhp:\
	:of=/usr/local/libexec/ofhp:

rattan|line|diablo|lp|Diablo 630 Line Printer:\
	:lp=:rm=rose:rp=rattan:sd=/var/spool/lpd/rattan:

bamboo|ps|PS|S|panasonic|Panasonic KX-P4455 PostScript v51.4:\
	:lp=:rm=rose:rp=bamboo:sd=/var/spool/lpd/bamboo:sc:
</code>
	    By using the <tt/sc/ capability, we prevent the use of
	    <tt/lpr -&num;/, but that still does not prevent users from
	    running 
	    <htmlurl url="http://www.freebsd.org/cgi/man.cgi?lpr"
	     name="lpr"> multiple times, or from submitting the
	    same file multiple times in one job like this:
<tscreen><verb>
lpr forsale.sign forsale.sign forsale.sign forsale.sign forsale.sign 
</verb></tscreen>
	    There are many ways to prevent this abuse (including
	    ignoring it) which you are free to explore.

	<sect2><heading>Restricting Access To Printers<label
	      id="printing:advanced:restricting:access"></heading>

	  <p> You can control who can print to what printers by using
	    the UNIX group mechanism and the <tt/rg/ capability in
	    <tt>/etc/printcap</tt>.  Just place the users you want to
	    have access to a printer in a certain group, and then name
	    that group in the <tt/rg/ capability.

	    Users outside the group (including root) will be greeted
	    with
<tscreen><verb>
lpr: Not a member of the restricted group
</verb></tscreen>
	    if they try to print to the controlled printer.

	    As with the <tt/sc/ (suppress multiple copies) capability,
	    you need to specify <tt/rg/ on remote hosts that also have
	    access to your printers, if you feel it is appropriate (see
	    section <ref name="Printers Installed on Remote Hosts"
	    id="printing:advanced:network:rm">).

	    For example, we will let anyone access the printer
	    <tt/rattan/, but only those in group <tt/artists/ can use
	    <tt/bamboo/.  Here is the familiar <tt>/etc/printcap</tt>
	    for host rose:
<code>
#
#  /etc/printcap for host rose - restricted group for bamboo
#
rattan|line|diablo|lp|Diablo 630 Line Printer:\
	:sh:sd=/var/spool/lpd/rattan:\
	:lp=/dev/lpt0:\
	:if=/usr/local/libexec/if-simple:

bamboo|ps|PS|S|panasonic|Panasonic KX-P4455 PostScript v51.4:\
	:sh:sd=/var/spool/lpd/bamboo:sc:rg=artists:\
	:lp=/dev/ttyd5:fs#0x82000e1:xs#0x820:rw:\
	:if=/usr/local/libexec/psif:\
	:df=/usr/local/libexec/psdf:
</code>
	    Let us leave the other example <tt>/etc/printcap</tt> file
	    (for the host orchid) alone.  Of course, anyone on orchid
	    can print to <tt/bamboo/.  It might be the case that we
	    only allow certain logins on orchid anyway, and want them
	    to have access to the printer.  Or not.

	    <em/Note:/ there can be only one restricted group per
	    printer.

	<sect2><heading>Controlling Sizes of Jobs Submitted<label
	      id="printing:advanced:restricting:sizes"></heading>

	  <p> If you have many users accessing the printers, you
	    probably need to put an upper limit on the sizes of the
	    files users can submit to print.  After all, there is only
	    so much free space on the filesystem that houses the
	    spooling directories, and you also need to make sure
	    there is room for the jobs of other users.

	    LPD enables you to limit the maximum byte size a file in a
	    job can be with the <tt/mx/ capability.  The units are in
	    BUFSIZ blocks, which are 1024 bytes.  If you put a zero
	    for this capability, there will be no limit on file size.
	    Note that the limit applies to <em/files/ in a job, and
	    <em/not/ the total job size.

	    LPD will not refuse a file that is larger than the limit you
	    place on a printer.  Instead, it will queue as much of the
	    file up to the limit, which will then get printed.  The
	    rest will be discarded.  Whether this is correct behavior
	    is up for debate.

	    Let us add limits to our example printers <tt/rattan/ and
	    <tt/bamboo/.  Since those artists' PostScript files tend
	    to be large, we will limit them to five megabytes.  We will
	    put no limit on the plain text line printer:
<code>
#
#  /etc/printcap for host rose
#

#
#  No limit on job size:
#
rattan|line|diablo|lp|Diablo 630 Line Printer:\
	:sh:sd=/var/spool/lpd/rattan:\
	:lp=/dev/lpt0:\
	:if=/usr/local/libexec/if-simple:

#
#  Limit of five megabytes:
#
bamboo|ps|PS|S|panasonic|Panasonic KX-P4455 PostScript v51.4:\
	:sh:sd=/var/spool/lpd/bamboo:sc:rg=artists:mx#5000:\
	:lp=/dev/ttyd5:fs#0x82000e1:xs#0x820:rw:\
	:if=/usr/local/libexec/psif:\
	:df=/usr/local/libexec/psdf:
</code>
	    Again, the limits apply to the local users only.  If
	    you have set up access to your printers remotely, remote
	    users will not get those limits.  You will need to specify the
	    <tt/mx/ capability in the remote <tt>/etc/printcap</tt>
	    files as well.  See section <ref name="Printers Installed
	    on Remote Hosts" id="printing:advanced:network:rm"> for
	    more information on remote printing.

	    There is another specialized way to limit job sizes from
	    remote printers; see section <ref
	    id="printing:advanced:restricting:remote"
	    name="Restricting Jobs from Remote Printers">.

	<sect2><heading>Restricting Jobs from Remote Printers<label
	      id="printing:advanced:restricting:remote"></heading>

	  <p> The LPD spooling system provides several ways to restrict
	    print jobs submitted from remote hosts:

	    <descrip>
	      <tag/Host restrictions/

		You can control from which remote hosts a local LPD
		accepts requests with the files
		<tt>/etc/hosts.equiv</tt> and <tt>/etc/hosts.lpd</tt>.
		LPD checks to see if an incoming request is from a
		host listed in either one of these files.  If not, LPD
		refuses the request.

		The format of these files is simple: one host name per
		line.  Note that the file <tt>/etc/hosts.equiv</tt> is
		also used by the 
		<htmlurl url="http://www.freebsd.org/cgi/man.cgi?ruserok(3)"
		name="ruserok(3)"> protocol, and affects
		programs like 
		<htmlurl url="http://www.freebsd.org/cgi/man.cgi?rsh"
		 name="rsh"> and 
		 <htmlurl url="http://www.freebsd.org/cgi/man.cgi?rcp"
		  name="rcp">, so be careful.

		For example, here is the <tt>/etc/hosts.lpd</tt> file
		on the host rose:
<code>
orchid
violet
madrigal.fishbaum.de
</code>
		This means rose will accept requests from the hosts
		orchid, violet, and madrigal.fishbaum.de.  If any
		other host tries to access rose's LPD, LPD will
		refuse them.

	      <tag/Size restrictions/

		You can control how much free space there needs to
		remain on the filesystem where a spooling directory
		resides.  Make a file called <tt/minfree/ in the
		spooling directory for the local printer.  Insert in
		that file a number representing how many disk blocks
		(512 bytes) of free space there has to be for a remote
		job to be accepted.

	        This lets you insure that remote users will not fill your
		filesystem.  You can also use it to give a certain
		priority to local users: they will be able to queue jobs
		long after the free disk space has fallen below the
		amount specified in the <tt/minfree/ file.

	        For example, let us add a <tt/minfree/ file for the
		printer <tt/bamboo/.  We examine
		<tt>/etc/printcap</tt> to find the spooling directory
		for this printer; here is <tt/bamboo/'s entry:
<tscreen><verb>
bamboo|ps|PS|S|panasonic|Panasonic KX-P4455 PostScript v51.4:\
	:sh:sd=/var/spool/lpd/bamboo:sc:rg=artists:mx#5000:\
	:lp=/dev/ttyd5:fs#0x82000e1:xs#0x820:rw:mx#5000:\
	:if=/usr/local/libexec/psif:\
	:df=/usr/local/libexec/psdf:
</verb></tscreen>
		The spooling directory is the given in the <tt/sd/
		capability.  We will make three megabytes (which is 6144
		disk blocks) the amount of free disk space that must
		exist on the filesystem for LPD to accept remote jobs:
<tscreen><verb>
echo 6144 > /var/spool/lpd/bamboo/minfree
</verb></tscreen>
	      <tag/User restrictions/

		You can control which remote users can print to local
		printers by specifying the <tt/rs/ capability in
		<tt>/etc/printcap</tt>.  When <tt/rs/ appears in the
		entry for a locally-attached printer, LPD will accept
		jobs from remote hosts <em/if/ the user submitting the
		job also has an account of the same login name on the
		local host.  Otherwise, LPD refuses the job.

	        This capability is particularly useful in an
		environment where there are (for example) different
		departments sharing a network, and some users
		transcend departmental boundaries.  By giving them
		accounts on your systems, they can use your printers
		from their own departmental systems.  If you would rather
		allow them to use <em/only/ your printers and not your
		compute resources, you can give them ``token''
		accounts, with no home directory and a useless shell
		like <tt>/usr/bin/false</tt>.
	    </descrip>

      <sect1><heading>Accounting for Printer Usage<label
	    id="printing:advanced:acct"></heading>

	<p> So, you need to charge for printouts.  And why not?  Paper
	  and ink cost money.  And then there are maintenance
	  costs---printers are loaded with moving parts and tend to
	  break down.  You have examined your printers, usage patterns,
	  and maintenance fees and have come up with a per-page (or
	  per-foot, per-meter, or per-whatever) cost.  Now, how do you
	  actually start accounting for printouts?

	  Well, the bad news is the LPD spooling system does not
	  provide much help in this department.  Accounting is highly
	  dependent on the kind of printer in use, the formats being
	  printed, and <em/your/ requirements in charging for printer
	  usage.

	  To implement accounting, you have to modify a printer's text
	  filter (to charge for plain text jobs) and the conversion
	  filters (to charge for other file formats), to count pages
	  or query the printer for pages printed.  You cannot get away
	  with using the simple output filter, since it cannot do
	  accounting.  See section <ref name="Filters"
	  id="printing:advanced:filter-intro">.

	  Generally, there are two ways to do accounting:
	  <itemize>
	    <item><em/Periodic accounting/ is the more common way,
	      possibly because it is easier.  Whenever someone prints a
	      job, the filter logs the user, host, and number of pages
	      to an accounting file.  Every month, semester, year, or
	      whatever time period you prefer, you collect the
	      accounting files for the various printers, tally up the
	      pages printed by users, and charge for usage.  Then you
	      truncate all the logging files, starting with a clean
	      slate for the next period.

	    <item><em/Timely accounting/ is less common, probably
	      because it is more difficult.  This method has the
	      filters charge users for printouts as soon as they use
	      the printers.  Like disk quotas, the accounting is
	      immediate.  You can prevent users from printing when
	      their account goes in the red, and might provide a way
	      for users to check and adjust their ``print quotas.''
	      But this method requires some database code to track
	      users and their quotas.
	  </itemize>

	  The LPD spooling system supports both methods easily: since
	  you have to provide the filters (well, most of the time),
	  you also have to provide the accounting code.  But there is
	  a bright side: you have enormous flexibility in your
	  accounting methods.  For example, you choose whether to use
	  periodic or timely accounting.  You choose what information
	  to log: user names, host names, job types, pages printed,
	  square footage of paper used, how long the job took to
	  print, and so forth.  And you do so by modifying the filters
	  to save this information.

	<sect2><heading>Quick and Dirty Printer Accounting</heading>

	  <p> FreeBSD comes with two programs that can get you set up
	    with simple periodic accounting right away.  They are the
	    text filter <tt/lpf/, described in section <ref
	    id="printing:advanced:lpf" name="lpf: a Text Filter">, and
	    
	    <htmlurl url="http://www.freebsd.org/cgi/man.cgi?pac"
	     name="pac">, a program to gather and total entries from
	    printer accounting files.

	    As mentioned in the section on filters (<ref
	      id="printing:advanced:filters" name="Filters">), LPD
	      starts the text and the conversion filters with the name
	      of the accounting file to use on the filter command
	      line.  The filters can use this argument to know where
	      to write an accounting file entry.  The name of this
	      file comes from the <tt/af/ capability in
	      <tt>/etc/printcap</tt>, and if not specified as an
	      absolute path, is relative to the spooling directory.

	    LPD starts <tt/lpf/ with page width and length arguments
	    (from the <tt/pw/ and <tt/pl/ capabilities).  <tt/lpf/
	    uses these arguments to determine how much paper will be
	    used.  After sending the file to the printer, it then
	    writes an accounting entry in the accounting file.  The
	    entries look like this:
<tscreen><verb>
   2.00 rose:andy
   3.00 rose:kelly
   3.00 orchid:mary
   5.00 orchid:mary
   2.00 orchid:zhang
</verb></tscreen>
	    You should use a separate accounting file for each
	    printer, as <tt/lpf/ has no file locking logic built into
	    it, and two <tt/lpf/s might corrupt each other's entries
	    if they were to write to the same file at the same time.
	    A easy way to insure a separate accounting file for each
	    printer is to use <tt/af=acct/ in <tt>/etc/printcap</tt>.
	    Then, each accounting file will be in the spooling directory
	    for a printer, in a file named <tt/acct/.

	    When you are ready to charge users for printouts, run the
	    
	    <htmlurl url="http://www.freebsd.org/cgi/man.cgi?pac"
	     name="pac"> program.  Just change to the spooling directory
	    for the printer you want to collect on and type 
	    <htmlurl url="http://www.freebsd.org/cgi/man.cgi?pac"
	     name="pac">.
	    You will get a dollar-centric summary like the following:
<code>
  Login               pages/feet   runs    price
orchid:kelly                5.00    1   $  0.10
orchid:mary                31.00    3   $  0.62
orchid:zhang                9.00    1   $  0.18
rose:andy                   2.00    1   $  0.04
rose:kelly                177.00  104   $  3.54
rose:mary                  87.00   32   $  1.74
rose:root                  26.00   12   $  0.52

total                     337.00  154   $  6.74
</code>
	    These are the arguments 
	    <htmlurl url="http://www.freebsd.org/cgi/man.cgi?pac"
	     name="pac"> expects:
	    <descrip>
	      <tag/<tt/-P<it/printer///

	        Which <it/printer/ to summarize.  This option works
		only if there is an absolute path in the <tt/af/
		capability in <tt>/etc/printcap</tt>.

	      <tag/<tt/-c//

		Sort the output by cost instead of alphabetically by
		user name.

	      <tag/<tt/-m//

		Ignore host name in the accounting files.  With this
		option, user smith on host alpha is the same user
		smith on host gamma.  Without, they are different users.

	      <tag/<tt/-p<it/price///

		Compute charges with <it/price/ dollars per page or
		per foot instead of the price from the <tt/pc/
		capability in <tt>/etc/printcap</tt>, or two cents (the
		default).  You can specify <it/price/ as a floating
		point number.

	      <tag/<tt/-r//

		Reverse the sort order.

	      <tag/<tt/-s//
	      
		Make an accounting summary file and truncate the
		accounting file.

	      <tag/<tt/<it/names...///

		Print accounting information for the given user
		<it/names/ only.
	    </descrip>

	    In the default summary that 
	    <htmlurl url="http://www.freebsd.org/cgi/man.cgi?pac"
	     name="pac"> produces, you see the
	    number of pages printed by each user from various hosts.
	    If, at your site, host does not matter (because users can
	    use any host), run <tt/pac -m/, to produce the following
	    summary:
<code>
  Login               pages/feet   runs    price
andy                        2.00    1   $  0.04
kelly                     182.00  105   $  3.64
mary                      118.00   35   $  2.36
root                       26.00   12   $  0.52
zhang                       9.00    1   $  0.18

total                     337.00  154   $  6.74
</code>
	    To compute the dollar amount due, 
	    <htmlurl url="http://www.freebsd.org/cgi/man.cgi?pac"
	     name="pac"> uses the
	    <tt/pc/ capability in the <tt>/etc/printcap</tt> file
	    (default of 200, or 2 cents per page).  Specify, in
	    hundredths of cents, the price per page or per foot you
	    want to charge for printouts in this capability.  You can
	    override this value when you run 
	    <htmlurl url="http://www.freebsd.org/cgi/man.cgi?pac"
	     name="pac"> with the <tt/-p/
	    option.  The units for the <tt/-p/ option are in dollars,
	    though, not hundredths of cents.  For example,
<tscreen><verb>
pac -p1.50
</verb></tscreen>
	    makes each page cost one dollar and fifty cents.  You can
	    really rake in the profits by using this option.

	    Finally, running <tt/pac -s/ will save the summary
	    information in a summary accounting file, which is named
	    the same as the printer's accounting file, but with
	    <tt/_sum/ appended to the name.  It then truncates the
	    accounting file.  When you run 
	    <htmlurl url="http://www.freebsd.org/cgi/man.cgi?pac"
	     name="pac"> again, it rereads
	    the summary file to get starting totals, then adds
	    information from the regular accounting file.


	<sect2><heading>How Can You Count Pages Printed?</heading>

	  <p> In order to perform even remotely accurate accounting,
	    you need to be able to determine how much paper a job
	    uses.  This is the essential problem of printer
	    accounting.

	    For plain text jobs, the problem's not that hard to solve:
	    you count how many lines are in a job and compare it to
	    how many lines per page your printer supports.  Do not
	    forget to take into account backspaces in the file which
	    overprint lines, or long logical lines that wrap onto one
	    or more additional physical lines.

	    The text filter <tt/lpf/ (introduced in <ref
	    id="printing:advanced:lpf" name="lpf: a Text Filter">)
	    takes into account these things when it does accounting.
	    If you are writing a text filter which needs to do
	    accounting, you might want to examine <tt/lpf/'s source
	    code.

	    How do you handle other file formats, though?

	    Well, for DVI-to-LaserJet or DVI-to-PostScript conversion,
	    you can have your filter parse the diagnostic output of
	    
	    <htmlurl url="http://www.freebsd.org/cgi/man.cgi?manpath=FreeBSD+Ports&amp;query=dvilj"
	     name="dvilj"> or 
	     <htmlurl url="http://www.freebsd.org/cgi/man.cgi?manpath=FreeBSD+Ports&amp;query=dvips"
	      name="dvips"> and look to see how many pages
	    were converted.  You might be able to do similar things
	    with other file formats and conversion programs.

	    But these methods suffer from the fact that the printer
	    may not actually print all those pages.  For example, it
	    could jam, run out of toner, or explode---and the user
	    would still get charged.

	    So, what can you do?

	    There is only one <em/sure/ way to do <em/accurate/
	    accounting.  Get a printer that can tell you how much
	    paper it uses, and attach it via a serial line or a
	    network connection.  Nearly all PostScript printers
	    support this notion.  Other makes and models do as well
	    (networked Imagen laser printers, for example).  Modify
	    the filters for these printers to get the page usage after
	    they print each job and have them log accounting
	    information based on that value <em/only/.  There is no
	    line counting nor error-prone file examination required.

	    Of course, you can always be generous and make all
	    printouts free.

    <sect><heading>Alternatives to the Standard Spooler<label
	  id="printing:lpd-alternatives"></heading> 

      <p> If you have been reading straight through this manual, by now
	you have learned just about everything there is to know about
	the LPD spooling system that comes with FreeBSD.  You can
	probably appreciate many of its shortcomings, which naturally
	leads to the question: ``What other spooling systems are out
	there (and work with FreeBSD)?''

	Unfortunately, I have located only <em/two/ alternatives---and
	they are almost identical to each other!  They are:
	<descrip>
	  <tag/PLP, the Portable Line Printer Spooler System/

	    PLP was based on software developed by Patrick Powell and
	    then maintained by an Internet-wide group of developers.
	    The main site for the software is at 
	    	    <htmlurl
	    url="ftp://ftp.iona.ie/pub/plp"
	    name="ftp://ftp.iona.ie/pub/plp">.  There is also a <htmlurl
	      url="http://www.iona.ie:8000/www/hyplan/jmason/plp.html"
	      name="web page">.

	    It is quite similar to the BSD LPD spooler, but boasts a
	    host of features, including:
	    <itemize>
	      <item>Better network support, including built-in support
		for networked printers, NIS-maintained printcaps, and
		NFS-mounted spooling directories

	      <item>Sophisticated queue management, allowing multiple
		printers on a queue, transfer of jobs between queues,
		and queue redirection

	      <item>Remote printer control functions

	      <item>Prioritization of jobs

	      <item>Expansive security and access options
	    </itemize>

	  <tag/LPRng/

	    LPRng, which purportedly means ``LPR: the Next
	    Generation'' is a complete rewrite of PLP.  Patrick Powell
	    and Justin Mason (the principal maintainer of PLP)
	    collaborated to make LPRng.  The main site for LPRng is
	    <htmlurl url="ftp://dickory.sdsu.edu/pub/LPRng"
	    name="ftp://dickory.sdsu.edu/pub/LPRng">.
	</descrip>


    <sect><heading>Acknowledgments</heading>

      <p> I would like to thank the following people who have assisted in
	the development of this document:

	<descrip>
	  <tag/Daniel Eischen <tt/&lt;deischen@iworks.interworks.org&gt;//

	    For providing a plethora of HP filter programs for perusal.

	  <tag/&a.jehamby;/

	    For the Ghostscript-to-HP filter.

	  <tag/My wife, Mary Kelly <tt/&lt;urquhart@argyre.colorado.edu&gt;//

	    For allowing me to spend more time with FreeBSD than with her.

	</descrip>