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        <th colspan="3" align="center">LPRng Reference Manual: 24
        Sep 2004 (For LPRng-3.8.28)</th>
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  <div class="SECT1">
    <h1 class="SECT1"><a name="AEN3103" id="AEN3103">4.11. Printcap
    Basics</a></h1>

    <p>In the previous sections we have used simple printcap
    entries to define how to set up filters and pass parameters to
    them. We will now examine the printcap database in more
    detail.</p>

    <p>The <b class="APPLICATION">LPRng</b> server and client
    software gets their configuration information from:</p>

    <ul>
      <li>
        <p>Compile time settings which set the default values for
        the configuration information.</p>
      </li>

      <li>
        <p>A <tt class="FILENAME">lpd.conf</tt> file that contains
        values that override the compile time defaults. This
        information can effect the behavior of the <b class=
        "APPLICATION">lpd</b> server and clients.</p>
      </li>

      <li>
        <p>Printcap entries which have configuration information
        for individual print queues. The information in the
        printcap entries for the queue override the <tt class=
        "FILENAME">lpd.conf</tt> and compile time defaults. The
        system printcap file is read first, followed by the user
        printcap file.</p>
      </li>

      <li>
        <p>Command line and environment variable values. These can
        be used to override or select particular configuration
        information or to select one of a set of options for
        use.</p>
      </li>
    </ul>

    <p>Each print queue or printer has a name which is used to look
    up the printcap information for the printer. The <tt class=
    "FILENAME">/etc/printcap</tt> file is the default location for
    the printcap information, although it can also be obtained from
    database servers, or generated by programs. See the <a href=
    "secnis.htm">Using Programs To Get Printcap Information</a>
    section for details.</p>

    <p>We will use a more complex printcap file to explore how
    <b class="APPLICATION">LPRng</b> gets the printcap information.
    Put the following lines in the <tt class=
    "FILENAME">/etc/printcap</tt> file:</p>

    <div class="INFORMALEXAMPLE">
      <a name="AEN3126" id="AEN3126"></a>
      <pre class="SCREEN">
# client entry
lp:tc=.client
lp2:tc=.client
.client:
  :lp=%P@localhost
  :force_localhost

lp:server
  :cm=The Main Print Queue
  :lp=/tmp/lp
  :tc=.common

lp2:server
  :cm=The Second Print Queue
  :lp=/tmp/lp2
  :tc=.common

.common:
  :sd=/var/spool/lpd/%P
  :mx=0
</pre>
    </div>The <tt class="COMMAND">lpc client</tt> command is very
    useful to see how <b class="APPLICATION">LPRng</b> uses this
    printcap information:

    <div class="INFORMALEXAMPLE">
      <a name="AEN3130" id="AEN3130"></a>
      <pre class="SCREEN">
<samp class="PROMPT">h4: {214} % </samp><kbd class=
"USERINPUT">lpc client</kbd>
Config
<samp class="PROMPT">h4: {215} % </samp><kbd class=
"USERINPUT">lpc client all</kbd>
Config
 :lpd_port=2000
 :printcap_path=/var/tmp/LPD/printcap

Names
 :.client=.client
 :.common=.common
 :lp=lp
 :lp2=lp2
 :main=lp

All
 :lp
 :lp2

Printcap Information
lp|main
 :force_localhost
 :lp=lp@localhost
lp2
 :force_localhost
 :lp=lp2@localhost
</pre>
    </div>

    <p>The <tt class="COMMAND">lpc client all</tt> command shows
    all of the configuration and printcap information, and is the
    handiest one for system debugging and diagnostics. The
    <span class="emphasis"><i class="EMPHASIS">Name</i></span>
    information is the names of the printcap entries that have been
    found in the database and is listed in sorted order. The
    <span class="emphasis"><i class="EMPHASIS">All</i></span> are
    entries that correspond to actual queues or printers and are
    listed in the order that they appear in the printcap or
    according to an order specified by the system administrator.
    (See the <a href="printcappath.htm#ALLPC"><tt class=
    "LITERAL">all</tt> Printcap Entry</a> for details.)</p>

    <div class="SECT2">
      <h2 class="SECT2"><a name="AEN3142" id="AEN3142">4.11.1.
      Printcap Processing Format</a></h2>

      <p>Queue or printer names must start with an alphanumeric
      character, and contain only alphanumerics, hyphens
      (<tt class="LITERAL">-</tt>) and underscores (<tt class=
      "LITERAL">_</tt>). To avoid known and nasty problems with
      sending and receiving print jobs from case sensitive and case
      insensitive systems, <b class="APPLICATION">LPRng</b>
      brutally lowercases all printcap entry names and printer
      names.</p>

      <p>The printcap file is processed by reading it line by line
      and composing the individual printcap entries. Each entry has
      an name and one or more aliases. The entries in the printcap
      assign values to options. These can have the format:</p>

      <div class="INFORMALEXAMPLE">
        <a name="AEN3149" id="AEN3149"></a>
        <pre class="SCREEN">
option=string value \n with escapes
flag         # equivalent to flag=1
flag@        # equivalent to flag=0
option#value # equivalent to option=value
</pre>
      </div>

      <p>An option will have the last value that occurs in the
      printcap entry.</p>

      <p>Our example shows the use of the <tt class=
      "LITERAL">tc</tt> (<span class="emphasis"><i class=
      "EMPHASIS">t</i></span>ermcap in<span class=
      "emphasis"><i class="EMPHASIS">c</i></span>lude) facility.
      The <tt class="LITERAL">:tc</tt> value is a list of printcap
      entries that should be prefixed to the <span class=
      "emphasis"><i class="EMPHASIS">start</i></span> of the
      printcap entry in which it appears. This allows options to be
      set in the printcap entry which will override the values in
      the <tt class="LITERAL">:tc</tt> included entry. For
      convenience, the options are displayed in sorted order.</p>

      <p>The <b class="APPLICATION">LPRng</b> clients and <b class=
      "APPLICATION">lpd</b> server may require a different set of
      options for the same spool queue. The clients require options
      whose values tell the clients how the contact the <b class=
      "APPLICATION">lpd</b> server and transfer a print job or
      query to it. The <b class="APPLICATION">lpd</b> server needs
      options that tell it how to either print a job or forward it
      to another <b class="APPLICATION">lpd</b> server. The
      <tt class="LITERAL">:client</tt> or <tt class=
      "LITERAL">:server</tt> option marks a printcap entry as for
      client or <b class="APPLICATION">lpd</b> server use only;
      unmarked entries are used by both server and client. The
      <tt class="COMMAND">lpc client</tt> command shows the
      printcap information that the <b class=
      "APPLICATION">LPRng</b> clients would use. For example, here
      is what the <b class="APPLICATION">lpd</b> server would
      use:</p>

      <div class="INFORMALEXAMPLE">
        <a name="AEN3171" id="AEN3171"></a>
        <pre class="SCREEN">
<samp class="PROMPT">h4: {216} % </samp><kbd class=
"USERINPUT">lpc server all</kbd>
Config
 :lpd_port=2000
 :printcap_path=/var/tmp/LPD/printcap

Names
 :.client=.client
 :.common=.common
 :lp=lp
 :lp2=lp2
 :main=lp

All
 :lp
 :lp2

Printcap Information
lp|main
 :cm=The Main Print Queue
 :force_localhost
 :lp=/tmp/lp
 :mx=0
 :sd=/var/spool/lpd/%P
 :server
lp2
 :cm=The Second Print Queue
 :force_localhost
 :lp=/tmp/lp2
 :mx=0
 :sd=/var/spool/lpd/%P
 :server
</pre>
      </div>

      <p>When we select the <tt class="LITERAL">server</tt>
      printcap information, we see that the <tt class=
      "LITERAL">:sd</tt> option has been added, and the <tt class=
      "LITERAL">:lp</tt> replaced with new values.</p>

      <p>We can use the <tt class="LITERAL">:oh</tt> (<tt class=
      "LITERAL">o</tt>n this <tt class="LITERAL">h</tt>ost) option
      to mark printcap entries for use by a selected set of hosts.
      For example:</p>

      <div class="INFORMALEXAMPLE">
        <a name="AEN3183" id="AEN3183"></a>
        <pre class="SCREEN">
lp:oh=10.0.0.0/255.255.255.0,*.private,!10.0.0.10
  :lp=%P@10.0.0.10
</pre>
      </div>

      <p>The <tt class="LITERAL">:oh</tt> option takes a list of IP
      addresses and masks or glob patterns, and applies these to
      the IP addresses or list of Fully Qualified Domain Names for
      the current host. If there is a for at least one IP address
      or pattern in the list match then the entry is used. An
      exclamation mark (<tt class="LITERAL">!</tt>) inverts the
      sense of the match, and the entry is used if the match
      fails.</p>

      <p>Finally, we can use the <tt class="LITERAL">wildcard</tt>
      facility to cause a default printcap entry to be used:</p>

      <div class="INFORMALEXAMPLE">
        <a name="AEN3190" id="AEN3190"></a>
        <pre class="SCREEN">
lp|*:cm=Wildcard Alias - %P=lp, %Q=wanted
  :lp=%P@10.0.0.10
*:cm=Wildcard Name- %P=wanted, %Q=wanted
  :lp=%P@10.0.0.10
</pre>
      </div>

      <p>The <b class="APPLICATION">LPRng</b> software first
      searches the printcap information for an exact match. If none
      is found then it searches for the first wildcard entry that
      matches the printer name. If the wildcard is used as an
      alias, then the printcap entry is simply selected for use,
      with the printer name and queue name selected as shown above.
      We can also use partial matching as well:</p>

      <div class="INFORMALEXAMPLE">
        <a name="AEN3194" id="AEN3194"></a>
        <pre class="SCREEN">
lp|lp_*
  :lp=%P@10.0.0.10
qt|qt_*
  :lp=%P@10.0.0.12
</pre>
      </div>

      <p>In the example above the first entry matches <tt class=
      "LITERAL">lp</tt> and all printer names starting with
      <tt class="LITERAL">lp_</tt>, while the second entry matches
      <tt class="LITERAL">qt</tt> and all printer names starting
      with <tt class="LITERAL">qt_</tt>. This can be useful when
      setting up a family of spool queues as discussed in later
      sections.</p>
    </div>

    <div class="SECT2">
      <h2 class="SECT2"><a name="AEN3201" id="AEN3201">4.11.2.
      Printcap Information From Programs and Databases</a></h2>

      <p>There many administrators store system information on a
      database server and having programs or utilities get their
      configuration information from this server. The use of the
      database allows easier system administration and also
      centralizes the administration. Rather than build in the
      various types of database access, the LPRng software allows
      the use of programs to obtain printcap information. This not
      only allows any type of database to be used, but also removes
      any legal or license restrictions on the redistribution of
      the actual software.</p>

      <p>We will use very simple example to show how you can use a
      program to get printcap information. First, you must
      configure the <b class="APPLICATION">LPRng</b> software to
      use a program to get the filter information. This is done by
      setting a value in the <tt class="FILENAME">lpc.conf</tt>
      file (usually <tt class="FILENAME">/etc/lpd.conf</tt> or
      <tt class="FILENAME">/usr/local/etc/lpd.conf</tt>). Copy your
      <tt class="FILENAME">lpd.conf</tt> file to <tt class=
      "FILENAME">lpd.conf.bak</tt> and then add the following line
      to the end of the file:</p>

      <div class="INFORMALEXAMPLE">
        <a name="AEN3211" id="AEN3211"></a>
        <pre class="SCREEN">
printcap_path=|/tmp/getpc

<samp class="PROMPT">h4: {217} % </samp><kbd class=
"USERINPUT">cd /etc</kbd>
<samp class="PROMPT">h4: {218} % </samp><kbd class=
"USERINPUT">cp lpd.conf lpd.conf.bak</kbd>
<samp class="PROMPT">h4: {219} % </samp><kbd class=
"USERINPUT">echo 'printcap_path=|/tmp/getpc' &gt;&gt;lpd.conf</kbd>
</pre>
      </div>

      <p>Next, edit the <tt class="FILENAME">/tmp/getpc</tt> file
      and set its values as shown below.</p>

      <div class="INFORMALEXAMPLE">
        <a name="AEN3221" id="AEN3221"></a>
        <pre class="SCREEN">
set /tmp/getpc:

  #!/bin/sh
  # /tmp/getpc
  echo PROG $0 "$@" &gt;&gt;/tmp/trace
  cat &gt;&gt;/tmp/trace
  cat &lt;&lt;EOF
  lp:lp=test@host
  EOF
  exit 0

<samp class="PROMPT">h4: {220} % </samp><kbd class=
"USERINPUT">chmod 755 /tmp/getpc</kbd>
<samp class="PROMPT">h4: {221} % </samp><kbd class=
"USERINPUT">echo testing | /tmp/getpc -aoption</kbd>
lp:lp=test@host
<samp class="PROMPT">h4: {222} % </samp><kbd class=
"USERINPUT">cat /tmp/trace</kbd>
PROG /tmp/getpc -aoption
testing
</pre>
      </div>

      <p>After you have tested the <b class="APPLICATION">getpc</b>
      script, use the <tt class="COMMAND">lpc client all</tt>
      command:</p>

      <div class="INFORMALEXAMPLE">
        <a name="AEN3232" id="AEN3232"></a>
        <pre class="SCREEN">
<samp class="PROMPT">h4: {223} % </samp><kbd class=
"USERINPUT">lpc client all</kbd>
Config
 :lockfile=/var/tmp/LPD/lpd
 :lpd_port=2000
 :printcap_path=|/tmp/getpc

Names
 :lp=lp

All
 :lp

Printcap Information
lp
 :lp=test@host
<samp class="PROMPT">h4: {224} % </samp><kbd class=
"USERINPUT">cat /tmp/trace</kbd>
<samp class="PROMPT">h4: {225} % </samp><kbd class=
"USERINPUT">cat /tmp/trace</kbd>
PROG /tmp/getpc -Pall -aacct -l66 -sstatus \
  -t2000-05-05-08:40:51.000 -w80 -x0 -y0 acct
all
PROG /tmp/getpc -Pall -aacct -l66 -sstatus \
  -t2000-05-05-08:40:51.000 -w80 -x0 -y0 acct
*
</pre>
      </div>

      <p>As seen from the <tt class="FILENAME">/tmp/trace</tt>
      file, the <tt class="COMMAND">getpc</tt> program is invoked
      with the standard filter parameters. The <tt class=
      "LITERAL">-P</tt> command line literal is set to the name of
      the printcap entry and the name of the entry is written to
      the filter's <acronym class="ACRONYM">STDIN</acronym>. If the
      entry is not found, then the wildcard printcap entry will be
      requested. The <tt class="LITERAL">-P</tt> literal is
      <span class="emphasis"><i class="EMPHASIS">not</i></span> set
      to <tt class="LITERAL">*</tt>, as this has the possibility of
      opening a security loophole when a shell script parses the
      filter's command line options.</p>

      <p>You restore the original <tt class=
      "FILENAME">lpd.conf</tt> file to restore the system to normal
      operation.</p>

      <div class="INFORMALEXAMPLE">
        <a name="AEN3250" id="AEN3250"></a>
        <pre class="SCREEN">
<samp class="PROMPT">h4: {226} % </samp><kbd class=
"USERINPUT">cd /etc</kbd>
<samp class="PROMPT">h4: {227} % </samp><kbd class=
"USERINPUT">cp lpd.conf.bak lpd.conf</kbd>
</pre>
      </div>

      <p>When using the program method to return information,
      special consideration should be given to the <tt class=
      "LITERAL">all</tt> request. If there is not an explicit
      <tt class="LITERAL">all</tt> entry, then the program should
      take appropriate steps to enumerate the values in the
      database, or report that there is a missing <tt class=
      "LITERAL">all</tt> entry to the appropriate administrative
      authority.</p>
    </div>

    <div class="SECT2">
      <h2 class="SECT2"><a name="AEN3260" id="AEN3260">4.11.3. User
      Printcap Information</a></h2>

      <p>In addition to the system printcap, each user can define a
      private printcap file that will be read after the system
      printcap. Users can define <b class="APPLICATION">LPRng</b>
      client entries and can augment the system printcap
      information.</p>

      <p>By default, <tt class="FILENAME">${HOME}/.printcap</tt> is
      the the user printcap file. Here is a simple example of a
      user printcap file.</p>

      <div class="INFORMALEXAMPLE">
        <a name="AEN3266" id="AEN3266"></a>
        <pre class="SCREEN">
# remote printer - default
lp:lp=raw@localhost
  :ifhp=model=laserjet4
  :filter=/usr/local/libexec/filters/ifhp
# direct connection to printer over TCP/IP connection
lp:lp=10.0.0.5%9100
  :direct
  :ifhp=model=phaser
  :filter=/usr/local/libexec/filters/ifhp
</pre>
      </div>

      <p>The two examples show how a simple printer definition can
      be created. The first example shows how to create a simple
      way to send a file directly to a remote print queue after
      passing it through a filter. This is usually called
      <span class="emphasis"><i class="EMPHASIS">client
      side</i></span> filtering.</p>

      <p>The second example is more interesting. Here we do the
      same thing, but we open a connection to the remote port on a
      host and send the print job. We do not spool the print job
      but send it directly. This is called <span class=
      "emphasis"><i class="EMPHASIS">lightweight lpr</i></span>
      printing.</p>

      <p>While the user printcap file is read after the system
      printcap file, the order of printcap entries is modified so
      that any entries that appeared in the user printcap file will
      appear before entries in the system printcap file. This
      allows users to modify the order in which printer entries are
      displayed.</p>
    </div>
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