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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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<h1 class="SECT1"><a name="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="AEN2003"></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>status
Printer Printing Spooling Jobs Server Subserver Redirect Status/(Debug)
lp@h4 enabled enabled 0 none none
lpc>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>quit
</pre>
</div>
<br>
<br>
<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 <var class="LITERAL">all</var> 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="AEN2028"></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>
<br>
<br>
<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="AEN2048"></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>
<br>
<br>
<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="AEN2075"></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>
<br>
<br>
<p>The <span class="emphasis"><i class=
"EMPHASIS">Rank</i></span> value of the first job has been
changed to <var class="LITERAL">active</var> 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="AEN2090"></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>
<br>
<br>
<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="AEN2116"></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>
<br>
<br>
<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="AEN2125"></a>
<pre class="SCREEN">
<samp class="PROMPT">h4: {151} %</samp> <kbd class=
"USERINPUT">lpc</kbd>
lpc>status
Printer Printing Spooling Jobs Server Subserver Redirect Status/(Debug)
lp@h4 enabled enabled 3 17990 17993
lpc>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>stop lp
Printer: lp@h4
lp@h4.private: stopped
lpc>start lp
Printer: lp@h4
lp@h4.private: started
lpc>quit
</pre>
</div>
<br>
<br>
<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="AEN2131"></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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