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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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        <td width="10%" align="left" valign="bottom"><a href=
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        <td width="80%" align="center" valign="bottom">Chapter 4.
        Print Spooling Tutorial</td>
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  <div class="SECT1">
    <h1 class="SECT1"><a name="CONTROLLINGPRINTQUEUE" id=
    "CONTROLLINGPRINTQUEUE">4.7. Controlling the Print
    Queue</a></h1>
    <p>The <b class="APPLICATION">lpc</b> command is used to
    examine and control the print server operation. The <tt class=
    "COMMAND">lpc status</tt> command displays the administrative
    status of a print queue. The <b class="APPLICATION">lpd</b>
    program caches status and job information in order to improve
    performance. The <tt class="COMMAND">lpc flush</tt> command
    will flush the cached information and cause the server to
    regenerate it. The <tt class="COMMAND">lpc enable</tt> and
    <tt class="COMMAND">lpc disable</tt> commands enable or disable
    spooling to the print queue, and the <tt class="COMMAND">lpc
    stop</tt> and <tt class="COMMAND">lpc start</tt> commands stop
    and start printing (or transfers) of jobs in the print
    queue.</p>
    <p>Let's look at the status displayed when we use these
    commands:</p>
    <div class="INFORMALEXAMPLE">
      <a name="AEN2001" id="AEN2001"></a>
      <pre class="SCREEN"><samp class=
      "PROMPT">h4: {120} % </samp><kbd class=
      "USERINPUT">lpc status</kbd>
 Printer  Printing Spooling Jobs Server Subserver Redirect Status/(Debug)
lp@h4      enabled  enabled    0   none    none
<samp class="PROMPT">h4: {121} % </samp><kbd class=
"USERINPUT">lpc status all</kbd>
 Printer  Printing Spooling Jobs Server Subserver Redirect Status/(Debug)
lp@h4      enabled  enabled    0    none    none
lp2@h4     enabled  enabled    0    none    none
<samp class="PROMPT">h4: {122} % </samp><kbd class=
"USERINPUT">lpc</kbd>
lpc&gt;status
 Printer  Printing Spooling Jobs Server Subserver Redirect Status/(Debug)
lp@h4      enabled  enabled    0    none    none
lpc&gt;status all
 Printer  Printing Spooling Jobs Server Subserver Redirect Status/(Debug)
lp@h4      enabled  enabled    0    none    none
lp2@h4     enabled  enabled    0    none    none
lpc&gt;quit</pre>
    </div>
    <p>The <b class="APPLICATION">lpc</b> command can be used in
    command line or interactive mode as shown above. When used with
    no parameters it will run in interactive mode, reading one or
    more commands from its standard input (<acronym class=
    "ACRONYM">STDIN</acronym>). The <tt class="COMMAND">lpc
    status</tt> command shows the administrative status of the
    select print queue. The <tt class="LITERAL">all</tt> queue name
    selects all print queues for display. As shown in the above
    example, both print queues have printing and spooling enabled
    and there are no jobs in the print queue. The <span class=
    "emphasis"><i class="EMPHASIS">Server</i></span> and
    <span class="emphasis"><i class="EMPHASIS">Subserver</i></span>
    information shows if there is a process which is printing jobs,
    and its helper process that does the actual communication with
    the printer.</p>
    <p>It might be puzzling at first why <b class=
    "APPLICATION">LPRng</b> uses two processes for this operation,
    but the reason is very simple. Many operating system
    implementations have <span class="emphasis"><i class=
    "EMPHASIS">memory leaks</i></span> that cause the actual
    process size to grow as it runs. This is especially true if a
    large number of databases such as the password, Domain Name
    Server, or other system database is consulted frequently with
    different queries. Since this is usually done quite a lot by
    the process which deals with the actual printing, the printing
    process would soon grow very large and then die when it could
    no longer obtain more memory. The <span class=
    "emphasis"><i class="EMPHASIS">Server</i></span> process will
    fork or create a child process <span class="emphasis"><i class=
    "EMPHASIS">Subserver</i></span> process that is responsible for
    the printing of a single job. When the job printing has been
    completed, the <span class="emphasis"><i class=
    "EMPHASIS">Subserver</i></span> process will exit and the
    <span class="emphasis"><i class="EMPHASIS">Server</i></span>
    process will then create another child until there are no more
    jobs to be printed. The <span class="emphasis"><i class=
    "EMPHASIS">Redirect</i></span> and <span class=
    "emphasis"><i class="EMPHASIS">Debug</i></span> fields will be
    discussed in later sections.</p>
    <p>Now let's use the basic spool queue control commands:</p>
    <div class="INFORMALEXAMPLE">
      <a name="AEN2026" id="AEN2026"></a>
      <pre class="SCREEN"><samp class=
      "PROMPT">h4: {123} % </samp><kbd class=
      "USERINPUT">lpc disable</kbd>
Printer: lp@h4
lp@h4.private: disabled
<samp class="PROMPT">h4: {124} % </samp><kbd class=
"USERINPUT">lpq</kbd>
Printer: lp@h4  (spooling disabled)
 Queue: no printable jobs in queue
<samp class="PROMPT">h4: {125} % </samp><kbd class=
"USERINPUT">lpc enable</kbd>
Printer: lp@h4
lp@h4.private: enabled
<samp class="PROMPT">h4: {126} % </samp><kbd class=
"USERINPUT">lpq</kbd>
Printer: lp@h4
 Queue: no printable jobs in queue
<samp class="PROMPT">h4: {127} % </samp><kbd class=
"USERINPUT">lpc stop</kbd>
Printer: lp@h4
lp@h4.private: stopped
<samp class="PROMPT">h4: {128} % </samp><kbd class=
"USERINPUT">lpq</kbd>
Printer: lp@h4  (printing disabled)
 Queue: no printable jobs in queue
<samp class="PROMPT">h4: {129} % </samp><kbd class=
"USERINPUT">lpc start</kbd>
Printer: lp@h4
lp@h4.private: started
<samp class="PROMPT">h4: {130} % </samp><kbd class=
"USERINPUT">lpq</kbd>
Printer: lp@h4
 Queue: no printable jobs in queue</pre>
    </div>
    <p>As we can see, the <b class="APPLICATION">lpc</b> command
    also reports on the status of the print queue. Let's see what
    happens when we print to a stopped queue:</p>
    <div class="INFORMALEXAMPLE">
      <a name="AEN2046" id="AEN2046"></a>
      <pre class="SCREEN"><samp class=
      "PROMPT">h4: {131} % </samp><kbd class=
      "USERINPUT">lpc stop</kbd>
Printer: lp@h4
lp@h4.private: stopped
<samp class="PROMPT">h4: {132} % </samp><kbd class=
"USERINPUT">lpr /tmp/hi</kbd>
<samp class="PROMPT">h4: {133} % </samp><kbd class=
"USERINPUT">lpr /tmp/hi /tmp/there</kbd>
<samp class="PROMPT">h4: {134} % </samp><kbd class=
"USERINPUT">lpq</kbd>
Printer: lp@h4  (printing disabled)
 Queue: 2 printable jobs
 Server: no server active
 Rank   Owner/ID               Class Job Files            Size Time
1      papowell@h4+17920         A 17920 /tmp/hi             3 18:14:22
2      papowell@h4+17922         A 17922 /tmp/hi,/tmp/there  9 18:14:30
<samp class="PROMPT">h4: {135} % </samp><kbd class=
"USERINPUT">lpc status</kbd>
 Printer  Printing Spooling Jobs  Server Subserver Redirect Status/(Debug)
lp@h4     disabled  enabled    2    none    none</pre>
    </div>
    <p>The <b class="APPLICATION">lpc</b> status shows that we have
    two jobs spooled. The <span class="emphasis"><i class=
    "EMPHASIS">Rank</i></span> field shows the order, the
    <tt class="FILENAME">Owner/ID</tt> shows the unique job ID that
    is assigned to the job and the <span class="emphasis"><i class=
    "EMPHASIS">Class</i></span> field is the job class (this may be
    changed with the <tt class="COMMAND">lpr -C class</tt> option).
    The <span class="emphasis"><i class="EMPHASIS">Job</i></span>
    field shows the <span class="emphasis"><i class="EMPHASIS">job
    number</i></span> assigned to this job in this particular spool
    queue. While the <acronym class="ACRONYM">ID</acronym> value
    never changes as a job moves through the <b class=
    "APPLICATION">LPRng</b> system, the <span class=
    "emphasis"><i class="EMPHASIS">job number</i></span> is
    specific to a particular spool queue and may change if a job is
    <span class="emphasis"><i class="EMPHASIS">forwarded</i></span>
    to another spool queue that has a job with the same job number.
    The <span class="emphasis"><i class="EMPHASIS">Size</i></span>
    field is the total number of printable bytes in the job, and
    the <span class="emphasis"><i class="EMPHASIS">Time</i></span>
    field shows the timestamp associated with the job.</p>
    <p>Now let's start the print queue and watch what happens.</p>
    <div class="INFORMALEXAMPLE">
      <a name="AEN2073" id="AEN2073"></a>
      <pre class="SCREEN"><samp class=
      "PROMPT">h4: {136} % </samp><kbd class=
      "USERINPUT">lpc start</kbd>
Printer: lp@h4
lp@h4.private: started
<samp class="PROMPT">h4: {137} % </samp><kbd class=
"USERINPUT">lpq</kbd>
Printer: lp@h4
 Queue: 2 printable jobs
 Server: pid 17928 active
 Unspooler: pid 17929 active
 Status: opening device '/tmp/lp' at 18:14:43.921
 Rank   Owner/ID             Class Job Files            Size Time
active papowell@h4+17920       A 17920 /tmp/hi             3 18:14:22
2      papowell@h4+17922       A 17922 /tmp/hi,/tmp/there  9 18:14:30
<samp class="PROMPT">h4: {138} % </samp><kbd class=
"USERINPUT">lpq -ll</kbd>
Printer: lp@h4
 Queue: 2 printable jobs
 Server: pid 17928 active
 Unspooler: pid 17929 active
 Status: printing job 'papowell@h4+17920' at 18:14:43.921
 Status: no banner at 18:14:43.921
 Status: printing data file 'dfA017920h4.private', size 57 at 18:14:43.922
 Rank   Owner/ID             Class Job Files            Size Time
active papowell@h4+17920       A 17920 /tmp/hi             3 18:14:22
2      papowell@h4+17922       A 17922 /tmp/hi,/tmp/there  9 18:14:30</pre>
    </div>
    <p>The <span class="emphasis"><i class=
    "EMPHASIS">Rank</i></span> value of the first job has been
    changed to <tt class="LITERAL">active</tt> and there is new
    <span class="emphasis"><i class="EMPHASIS">Status</i></span>
    information. If we use <tt class="COMMAND">lpq -ll</tt> we can
    see the times that the various print operations are carried
    out, and details of their success or failure.</p>
    <p>We can also use the <b class="APPLICATION">lpc</b> command
    to see the status of a particular job. We can select jobs by
    the user name, the ID, or the job number. For example:</p>
    <div class="INFORMALEXAMPLE">
      <a name="AEN2088" id="AEN2088"></a>
      <pre class="SCREEN"><samp class=
      "PROMPT">h4: {139} % </samp><kbd class=
      "USERINPUT">lpc stop</kbd>
Printer: lp@h4
lp@h4.private: stopped
<samp class="PROMPT">h4: {140} % </samp><kbd class=
"USERINPUT">echo hi |lpr</kbd>
<samp class="PROMPT">h4: {141} % </samp><kbd class=
"USERINPUT">echo there | lpr</kbd>
<samp class="PROMPT">h4: {142} % </samp><kbd class=
"USERINPUT">echo test |lpr</kbd>
<samp class="PROMPT">h4: {143} % </samp><kbd class=
"USERINPUT">lpq</kbd>
Printer: lp@h4  (printing disabled)
 Queue: 3 printable jobs
 Server: no server active
 Status: job 'papowell@h4+17922' removed at 18:15:13.981
 Rank   Owner/ID            Class Job Files           Size Time
1      papowell@h4+17959      A 17959 (stdin)            3 18:23:24
2      papowell@h4+17962      A 17962 (stdin)            6 18:23:30
3      papowell@h4+17970      A 17970 (stdin)            5 18:23:35
<samp class="PROMPT">h4: {144} % </samp><kbd class=
"USERINPUT">lpq 17970</kbd>
Printer: lp@h4  (printing disabled)
 Queue: 3 printable jobs
 Server: no server active
 Status: job 'papowell@h4+17922' removed at 18:15:13.981
 Rank   Owner/ID            Class Job Files           Size Time
3      papowell@h4+17970      A 17970 (stdin)            5 18:23:35
<samp class="PROMPT">h4: {145} % </samp><kbd class=
"USERINPUT">lpq papowell</kbd>
Printer: lp@h4  (printing disabled)
 Queue: 3 printable jobs
 Server: no server active
 Status: job 'papowell@h4+17922' removed at 18:15:13.981
 Rank   Owner/ID            Class Job Files           Size Time
1      papowell@h4+17959      A 17959 (stdin)            3 18:23:24
2      papowell@h4+17962      A 17962 (stdin)            6 18:23:30
3      papowell@h4+17970      A 17970 (stdin)            5 18:23:35
<samp class="PROMPT">h4: {146} % </samp><kbd class=
"USERINPUT">lpq -s 17970</kbd>
lp@h4  1 jobs
<samp class="PROMPT">h4: {147} % </samp><kbd class=
"USERINPUT">lpq -s papowell</kbd>
lp@h4  3 jobs
<samp class="PROMPT">h4: {148} % </samp><kbd class=
"USERINPUT">lpq -s nobody</kbd>
lp@h4  0 jobs</pre>
    </div>
    <p>We use <tt class="COMMAND">lpq -Pqueuename</tt> to select a
    specific print queue and <tt class="COMMAND">lpq -a</tt> or
    <tt class="COMMAND">lpq -Pall</tt> to select all queues:</p>
    <div class="INFORMALEXAMPLE">
      <a name="AEN2114" id="AEN2114"></a>
      <pre class="SCREEN"><samp class=
      "PROMPT">h4: {149} % </samp><kbd class=
      "USERINPUT">lpc -a stop</kbd>
Printer: lp@h4
lp@h4.private: stopped
Printer: lp2@h4
lp2@h4.private: stopped
<samp class="PROMPT">h4: {150} % </samp><kbd class=
"USERINPUT">lpc -Pall start</kbd>
Printer: lp@h4
lp@h4.private: started
Printer: lp2@h4
lp2@h4.private: started</pre>
    </div>
    <p>You can use the <b class="APPLICATION">lpc</b> command in
    <span class="emphasis"><i class=
    "EMPHASIS">interactive</i></span> mode:</p>
    <div class="INFORMALEXAMPLE">
      <a name="AEN2123" id="AEN2123"></a>
      <pre class="SCREEN"><samp class=
      "PROMPT">h4: {151} % </samp><kbd class="USERINPUT">lpc</kbd>
lpc&gt;status
 Printer  Printing Spooling Jobs  Server Subserver Redirect Status/(Debug)
lp@h4      enabled  enabled    3    17990   17993
lpc&gt;status all
 Printer  Printing Spooling Jobs  Server Subserver Redirect Status/(Debug)
lp@h4      enabled  enabled    3    17990   17993
lp2@h4     enabled  enabled    3    none    none
lpc&gt;stop lp
Printer: lp@h4
lp@h4.private: stopped
lpc&gt;start lp
Printer: lp@h4
lp@h4.private: started
lpc&gt;quit</pre>
    </div>
    <p>The <tt class="COMMAND">lpc topq</tt> command can be used to
    put a job (or jobs) at the head of the spool queue. This
    command is very useful when some job requires priority service.
    You can select the job by using the job number or the job
    ID.</p>
    <div class="INFORMALEXAMPLE">
      <a name="AEN2129" id="AEN2129"></a>
      <pre class="SCREEN"><samp class=
      "PROMPT">h4: {152} % </samp><kbd class=
      "USERINPUT">lpc topq lp 17970</kbd>
Printer: lp@h4
lp: selected 'papowell@h4+17970'
lp@h4.private: started
<samp class="PROMPT">h4: {153} % </samp><kbd class=
"USERINPUT">lpq</kbd>
Printer: lp@h4
 Queue: 3 printable jobs
 Server: pid 17999 active
 Rank   Owner/ID          Class Job Files      Size Time
active papowell@h4+17970    A 17970 (stdin)      5 18:23:35
1      papowell@h4+17959    A 17959 (stdin)      3 18:23:24
2      papowell@h4+17962    A 17962 (stdin)      6 18:23:30</pre>
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