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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<th colspan="3" align="center">LPRng-HOWTO: 1 Apr 2002
(For LPRng-3.8.10)</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.
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<div class="SECT1">
<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="AEN1950"></a>
<pre class="SCREEN">
<tt class="PROMPT">h4: {120} %</tt> <tt class=
"USERINPUT"><b>lpc status</b></tt>
Printer Printing Spooling Jobs Server Subserver Redirect Status/(Debug)
lp@h4 enabled enabled 0 none none
<tt class="PROMPT">h4: {121} %</tt> <tt class=
"USERINPUT"><b>lpc status all</b></tt>
Printer Printing Spooling Jobs Server Subserver Redirect Status/(Debug)
lp@h4 enabled enabled 0 none none
lp2@h4 enabled enabled 0 none none
<tt class="PROMPT">h4: {122} %</tt> <tt class=
"USERINPUT"><b>lpc</b></tt>
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 (<span class=
"ACRONYM">STDIN</span>). 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 <i
class="EMPHASIS">Server</i> and <i class=
"EMPHASIS">Subserver</i> 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 <i class="EMPHASIS">memory
leaks</i> 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 <i class="EMPHASIS">Server</i>
process will fork or create a child process <i class=
"EMPHASIS">Subserver</i> process that is responsible for the
printing of a single job. When the job printing has been
completed, the <i class="EMPHASIS">Subserver</i> process will
exit and the <i class="EMPHASIS">Server</i> process will then
create another child until there are no more jobs to be
printed. The <i class="EMPHASIS">Redirect</i> and <i class=
"EMPHASIS">Debug</i> 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="AEN1975"></a>
<pre class="SCREEN">
<tt class="PROMPT">h4: {123} %</tt> <tt class=
"USERINPUT"><b>lpc disable</b></tt>
Printer: lp@h4
lp@h4.private: disabled
<tt class="PROMPT">h4: {124} %</tt> <tt class=
"USERINPUT"><b>lpq</b></tt>
Printer: lp@h4 (spooling disabled)
Queue: no printable jobs in queue
<tt class="PROMPT">h4: {125} %</tt> <tt class=
"USERINPUT"><b>lpc enable</b></tt>
Printer: lp@h4
lp@h4.private: enabled
<tt class="PROMPT">h4: {126} %</tt> <tt class=
"USERINPUT"><b>lpq</b></tt>
Printer: lp@h4
Queue: no printable jobs in queue
<tt class="PROMPT">h4: {127} %</tt> <tt class=
"USERINPUT"><b>lpc stop</b></tt>
Printer: lp@h4
lp@h4.private: stopped
<tt class="PROMPT">h4: {128} %</tt> <tt class=
"USERINPUT"><b>lpq</b></tt>
Printer: lp@h4 (printing disabled)
Queue: no printable jobs in queue
<tt class="PROMPT">h4: {129} %</tt> <tt class=
"USERINPUT"><b>lpc start</b></tt>
Printer: lp@h4
lp@h4.private: started
<tt class="PROMPT">h4: {130} %</tt> <tt class=
"USERINPUT"><b>lpq</b></tt>
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="AEN1995"></a>
<pre class="SCREEN">
<tt class="PROMPT">h4: {131} %</tt> <tt class=
"USERINPUT"><b>lpc stop</b></tt>
Printer: lp@h4
lp@h4.private: stopped
<tt class="PROMPT">h4: {132} %</tt> <tt class=
"USERINPUT"><b>lpr /tmp/hi</b></tt>
<tt class="PROMPT">h4: {133} %</tt> <tt class=
"USERINPUT"><b>lpr /tmp/hi /tmp/there</b></tt>
<tt class="PROMPT">h4: {134} %</tt> <tt class=
"USERINPUT"><b>lpq</b></tt>
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
<tt class="PROMPT">h4: {135} %</tt> <tt class=
"USERINPUT"><b>lpc status</b></tt>
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 <i class="EMPHASIS">Rank</i> field
shows the order, the <tt class="FILENAME">Owner/ID</tt> shows
the unique job ID that is assigned to the job and the <i
class="EMPHASIS">Class</i> field is the job class (this may
be changed with the <tt class="COMMAND">lpr -C class</tt>
option). The <i class="EMPHASIS">Job</i> field shows the <i
class="EMPHASIS">job number</i> assigned to this job in this
particular spool queue. While the <span class=
"ACRONYM">ID</span> value never changes as a job moves
through the <b class="APPLICATION">LPRng</b> system, the <i
class="EMPHASIS">job number</i> is specific to a particular
spool queue and may change if a job is <i class=
"EMPHASIS">forwarded</i> to another spool queue that has a
job with the same job number. The <i class=
"EMPHASIS">Size</i> field is the total number of printable
bytes in the job, and the <i class="EMPHASIS">Time</i> 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="AEN2022"></a>
<pre class="SCREEN">
<tt class="PROMPT">h4: {136} %</tt> <tt class=
"USERINPUT"><b>lpc start</b></tt>
Printer: lp@h4
lp@h4.private: started
<tt class="PROMPT">h4: {137} %</tt> <tt class=
"USERINPUT"><b>lpq</b></tt>
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
<tt class="PROMPT">h4: {138} %</tt> <tt class=
"USERINPUT"><b>lpq -ll</b></tt>
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 <i class="EMPHASIS">Rank</i> value of the first job
has been changed to <tt class="LITERAL">active</tt> and there
is new <i class="EMPHASIS">Status</i> 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="AEN2037"></a>
<pre class="SCREEN">
<tt class="PROMPT">h4: {139} %</tt> <tt class=
"USERINPUT"><b>lpc stop</b></tt>
Printer: lp@h4
lp@h4.private: stopped
<tt class="PROMPT">h4: {140} %</tt> <tt class=
"USERINPUT"><b>echo hi |lpr</b></tt>
<tt class="PROMPT">h4: {141} %</tt> <tt class=
"USERINPUT"><b>echo there | lpr</b></tt>
<tt class="PROMPT">h4: {142} %</tt> <tt class=
"USERINPUT"><b>echo test |lpr</b></tt>
<tt class="PROMPT">h4: {143} %</tt> <tt class=
"USERINPUT"><b>lpq</b></tt>
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
<tt class="PROMPT">h4: {144} %</tt> <tt class=
"USERINPUT"><b>lpq 17970</b></tt>
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
<tt class="PROMPT">h4: {145} %</tt> <tt class=
"USERINPUT"><b>lpq papowell</b></tt>
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
<tt class="PROMPT">h4: {146} %</tt> <tt class=
"USERINPUT"><b>lpq -s 17970</b></tt>
lp@h4 1 jobs
<tt class="PROMPT">h4: {147} %</tt> <tt class=
"USERINPUT"><b>lpq -s papowell</b></tt>
lp@h4 3 jobs
<tt class="PROMPT">h4: {148} %</tt> <tt class=
"USERINPUT"><b>lpq -s nobody</b></tt>
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="AEN2063"></a>
<pre class="SCREEN">
<tt class="PROMPT">h4: {149} %</tt> <tt class=
"USERINPUT"><b>lpc -a stop</b></tt>
Printer: lp@h4
lp@h4.private: stopped
Printer: lp2@h4
lp2@h4.private: stopped
<tt class="PROMPT">h4: {150} %</tt> <tt class=
"USERINPUT"><b>lpc -Pall start</b></tt>
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
<i class="EMPHASIS">interactive</i> mode:</p>
<div class="INFORMALEXAMPLE">
<a name="AEN2072"></a>
<pre class="SCREEN">
<tt class="PROMPT">h4: {151} %</tt> <tt class=
"USERINPUT"><b>lpc</b></tt>
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="AEN2078"></a>
<pre class="SCREEN">
<tt class="PROMPT">h4: {152} %</tt> <tt class=
"USERINPUT"><b>lpc topq lp 17970</b></tt>
Printer: lp@h4
lp: selected 'papowell@h4+17970'
lp@h4.private: started
<tt class="PROMPT">h4: {153} %</tt> <tt class=
"USERINPUT"><b>lpq</b></tt>
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>
</div>
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