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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
15. Job Processing</td>
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<div class="SECT1">
<h1 class="SECT1"><a name="OPENDEVICE">15.4. Opening the
Output Device</a></h1>
<p>Options used:</p>
<ul>
<li>
<p><tt class="LITERAL">achk</tt> FLAG <i class=
"EMPHASIS">Accounting check at start</i></p>
</li>
<li>
<p><tt class="LITERAL">af=</tt><i class=
"EMPHASIS">Accounting File</i></p>
</li>
<li>
<p><tt class="LITERAL">ar</tt> FLAG <i class=
"EMPHASIS">Remote printer accounting enabled</i></p>
</li>
<li>
<p><tt class="LITERAL">as=</tt><i class=
"EMPHASIS">Accounting at start</i></p>
</li>
<li>
<p><tt class="LITERAL">connect_grace=</tt><i class=
"EMPHASIS">Time between jobs</i></p>
</li>
<li>
<p><tt class="LITERAL">connect_interval=</tt><i class=
"EMPHASIS">Connection interval</i></p>
</li>
<li>
<p><tt class="LITERAL">connect_timeout=</tt><i class=
"EMPHASIS">Connection timeout</i></p>
</li>
<li>
<p><tt class="LITERAL">control_filter=</tt><i class=
"EMPHASIS">Control file filter</i></p>
</li>
<li>
<p><tt class="LITERAL">ff=</tt><i class="EMPHASIS">form
feed</i></p>
</li>
<li>
<p><tt class="LITERAL">fo</tt> FLAG <i class=
"EMPHASIS">form feed on open</i></p>
</li>
<li>
<p><tt class="LITERAL">la</tt> FLAG <i class=
"EMPHASIS">Local printer accounting enabled</i></p>
</li>
<li>
<p><tt class="LITERAL">ld=</tt><i class="EMPHASIS">leader
on open (initialization string)</i></p>
</li>
<li>
<p><tt class="LITERAL">lk</tt> FLAG <i class=
"EMPHASIS">Lock IO device</i></p>
</li>
<li>
<p><tt class="LITERAL">lp=</tt><i class="EMPHASIS">IO
device pathname</i></p>
</li>
<li>
<p><tt class="LITERAL">nb</tt> FLAG <i class=
"EMPHASIS">Nonblocking device open</i></p>
</li>
<li>
<p><tt class="LITERAL">network_connect_grace=</tt><i
class="EMPHASIS">Interval in secs between jobs</i></p>
</li>
<li>
<p><tt class="LITERAL">of=</tt><i class="EMPHASIS">of
filter</i></p>
</li>
<li>
<p><tt class="LITERAL">retry_econnrefused</tt> FLAG <i
class="EMPHASIS">Retry if open failed</i></p>
</li>
<li>
<p><tt class="LITERAL">retry_nolink</tt> FLAG <i class=
"EMPHASIS">Retry if open failed</i></p>
</li>
<li>
<p><tt class="LITERAL">rm=</tt><i class="EMPHASIS">the
remote machine to send the job to</i></p>
</li>
<li>
<p><tt class="LITERAL">rp=</tt><i class="EMPHASIS">the
remote print queue to send the job to</i></p>
</li>
<li>
<p><tt class="LITERAL">rw</tt> FLAG <i class=
"EMPHASIS">device opened RW flag</i></p>
</li>
<li>
<p><tt class="LITERAL">server_tmp_dir=</tt><i class=
"EMPHASIS">temporary directory</i></p>
</li>
</ul>
Sequence of Operations:
<ol type="1">
<li>
<p>During the server operations, it will try to create
temporary files in the print queue spool directory. If
this is not desirable, it will create them in the <tt
class="LITERAL">server_tmp_dir</tt> directory.</p>
</li>
<li>
<p>If the accounting file specified by <tt class=
"LITERAL">af</tt> exists, it is opened (af_fd) and the
af_fd is passed as file descriptor 3 to all filters. If
the <tt class="LITERAL">af</tt> value has the form <tt
class="LITERAL">af=|/program</tt> then the program is
started and the program <span class=
"ACRONYM">STDIN</span> is used as af_fd. If the <tt
class="LITERAL">af</tt> value has the form <tt class=
"LITERAL">af=host%port</tt>, then a TCP/IP connection to
the corresponding port on the remote host is made and the
port used as af_fd. In the latter two cases, the filter
<span class="ACRONYM">STDIN</span> (file descriptor 0) is
actually opened read/write, and is used when information
is needed from the accounting filter or remote server.
See <a href=
"accountingref.htm#ACCOUNTINGSERVER">Accounting Printcap
Options</a> for more information on the <b class=
"APPLICATION">LPRng</b> accounting support.</p>
</li>
<li>
<p><a name="ACCOUNTSTART"></a> If <tt class=
"LITERAL">la</tt> (local accounting) is true and we are
printing a job or <tt class="LITERAL">ar</tt> (remote
accounting) is true and we are transferring a job, the
<tt class="LITERAL">as</tt> value is examined. If it is a
filter (program) specification, then the program is
started with its <span class="ACRONYM">STDIN</span>
attached to <tt class="FILENAME">/dev/null</tt>, <span
class="ACRONYM">STDOUT</span> will be read by the print
spooler, <span class="ACRONYM">STDERR</span> output will
be written to the error log, and file descriptor 3 output
will be appended to the accounting file. The lpd program
will wait until the accounting filter program terminates,
and examine the error code for action, as for the filters
(see <a href="printingjob.htm#ERRORCODES">errorcodes</a>
below). If the exit status is 0, (JSUCC) then the
printing process will continue, if JHOLD the job will be
held, if JREMOVE the job will be removed, if JFAIL the
job processing will terminate with a JFAIL indication,
otherwise the job processing will terminate with a JABORT
indication.</p>
</li>
<li>
<p>If the accounting filter exited with a JSUCC (no error
code) and the <tt class="LITERAL">achk</tt> (accounting
check) flag is set, the line read from the accounting
filter <span class="ACRONYM">STDOUT</span> will be
examined. This line should be <tt class=
"LITERAL">accept</tt>, <tt class="LITERAL">hold</tt>, <tt
class="LITERAL">fail</tt>, <tt class=
"LITERAL">remove</tt>, otherwise the job processing
terminates with a JABORT indication. An <tt class=
"LITERAL">accept</tt> will allow the job to be printed,
<tt class="LITERAL">hold</tt> will hold the job, <tt
class="LITERAL">fail</tt> will cause the job to fail, <tt
class="LITERAL">remove</tt> will cause the job to be
removed.</p>
</li>
<li>
<p>If the <tt class="LITERAL">connect_grace</tt> value is
non-zero and the server is opening a device or <tt class=
"LITERAL">network_connect_grace</tt> is non-zero and a
network connection is being made, the server will pause
the specified time. This is to accommodate devices which
need a recovery time between jobs.</p>
</li>
<li>
<p>The <tt class="LITERAL">lp</tt> option is checked to
determine the type of IO device.</p>
<div class="INFORMALTABLE">
<a name="AEN7025"></a>
<table border="1" class="CALSTABLE">
<thead>
<tr>
<th align="LEFT" valign="TOP">Format</th>
<th align="LEFT" valign="TOP">Meaning</th>
</tr>
</thead>
<tbody>
<tr>
<td align="LEFT" valign="TOP"><tt class=
"FILENAME">/pathname</tt></td>
<td align="LEFT" valign="TOP">Absolute pathname
of IO device</td>
</tr>
<tr>
<td align="LEFT" valign="TOP"><tt class=
"LITERAL">pr@host</tt></td>
<td align="LEFT" valign="TOP">transfer to <tt
class="LITERAL">pr</tt> on remote <tt class=
"LITERAL">host</tt></td>
</tr>
<tr>
<td align="LEFT" valign="TOP"><tt class=
"LITERAL">host%port</tt></td>
<td align="LEFT" valign="TOP">open a TCP/IP
connection to port on host. host can be name or
IP address</td>
</tr>
<tr>
<td align="LEFT" valign="TOP"><tt class=
"LITERAL">|filter</tt></td>
<td align="LEFT" valign="TOP">run the filter
program; it <span class="ACRONYM">STDIN</span>
will be used as device</td>
</tr>
</tbody>
</table>
</div>
<br>
<br>
</li>
<li>
<p>The IO device specified by <tt class="LITERAL">lp</tt>
is opened write-only or read-write if the <tt class=
"LITERAL">rw</tt> flag is true, and the resulting file
descriptor is io_fd. If the <tt class="LITERAL">nb</tt>
flag is set, a non-blocking open will be done as well. If
the <tt class="LITERAL">lk</tt> (lock device) flag is
true, the device will be locked against use by other <b
class="APPLICATION">lpd</b> servers.</p>
</li>
<li>
<p>If a <tt class="LITERAL">host%port</tt> combination, a
TCP/IP connection will be opened to the remote port and
the connection will be used as io_fd.</p>
</li>
<li>
<p>If a filter program is specified, the filter program
will be run and the <span class="ACRONYM">STDIN</span> of
the filter will be used as the device file
descriptor.</p>
</li>
<li>
<p>If a <tt class="LITERAL">rp@rm</tt> combination, or
none of the above combinations are true and the <tt
class="LITERAL">rm</tt> and <tt class="LITERAL">rp</tt>
values are non-zero, then the job will be transferred to
a remote printer. The type of operation will be a job
transfer, rather than printing operation.</p>
</li>
<li>
<p>If the <tt class="LITERAL">connect_timeout</tt> value
is non-zero, a timeout is setup for the device or socket
open. If the device or connection open does not succeed
within the timeout, then the open operation fails.</p>
</li>
<li>
<p>If a connection is to a network address (i.e. - <tt
class="FUNCTION">connect()</tt> system call) and the
connection attempt fails with an <span class=
"ACRONYM">ECONNREFUSED</span> error, if the <tt class=
"LITERAL">retry_econnrefused</tt> flag is set then the
connection attempt is retried, but this time using an
alternative port number. See <a href=
"rfc1179ref.htm">RFC1179</a> for details. This is
repeated until all of the possible originating port
numbers are exhausted.</p>
</li>
<li>
<p>If the open or connect operation fails, and the <tt
class="LITERAL">retry_nolink</tt> flag is set, then the
server will pause for a minimum of <tt class=
"LITERAL">connect_grace</tt> plus a multiple of <tt
class="LITERAL">connect_interval</tt> seconds based on
the number of attempts before retrying the open
operation. Note that the interval may increase as the
number of attempts increases.</p>
</li>
<li>
<p>If printing a job and the <tt class="LITERAL">:of</tt>
filter is specified, it is created with its <span class=
"ACRONYM">STDOUT</span> (fd 1) attached to the io_fd. Its
stdin (of_fd) will be used in the steps listed below. If
there is no <tt class="LITERAL">:of</tt> filter, then the
of_fd value will be the io_fd descriptor.</p>
</li>
<li>
<p>If transferring a job and the <tt class=
"LITERAL">control_filter</tt> option is specified, then
the program specified by the <tt class=
"LITERAL">control_filter</tt> value will be run. It will
have its <span class="ACRONYM">STDIN</span> set to the
control file, and its <span class="ACRONYM">STDOUT</span>
output will be used as the new value of the control file
to transfer to the remote host. See <a href=
"filteroptions.htm">Filter Command Line Options and
Environment Variables</a> for details of options passed
to the control filter, and <a href=
"printingjob.htm#ERRORCODES">errorcodes</a> for the exit
codes of the filter.</p>
</li>
<li>
<p>If the operation is a job transfer, the operation
proceeds as outlined in <a href=
"rfc1179ref.htm">RFC1179</a>, and then the <a href=
"normalterm.htm">Normal Termination</a> operations are
carried out.</p>
</li>
<li>
<p>If the operation is a print operation and the <tt
class="LITERAL">ld</tt> (leader on open) value is
provided, the string is translated (escapes removed) and
written to the of_fd file descriptor.</p>
</li>
<li>
<p>If the <tt class="LITERAL">fo</tt> (form feed on open)
flag is true, then the <tt class="LITERAL">ff</tt> (form
feed) string is translated (escapes removed) and written
to the of_fd file descriptor.</p>
</li>
</ol>
<br>
<br>
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