<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<meta name="generator" content="HTML Tidy, see www.w3.org">
<title>Queue Lock File</title>
<meta name="GENERATOR" content=
"Modular DocBook HTML Stylesheet Version 1.7">
<link rel="HOME" title=" LPRng Reference Manual" href=
"index.htm">
<link rel="UP" title="Spool Queues and Files" href=
"spoolqueue.htm">
<link rel="PREVIOUS" title="Spool Queues and Files" href=
"spoolqueue.htm">
<link rel="NEXT" title="Spool Control File " href=
"queuecontrolfile.htm">
</head>
<body class="SECT1" bgcolor="#FFFFFF" text="#000000" link=
"#0000FF" vlink="#840084" alink="#0000FF">
<div class="NAVHEADER">
<table summary="Header navigation table" width="100%" border=
"0" cellpadding="0" cellspacing="0">
<tr>
<th colspan="3" align="center">LPRng Reference Manual: 24
Sep 2004 (For LPRng-3.8.28)</th>
</tr>
<tr>
<td width="10%" align="left" valign="bottom"><a href=
"spoolqueue.htm" accesskey="P">Prev</a></td>
<td width="80%" align="center" valign="bottom">Chapter
13. Spool Queues and Files</td>
<td width="10%" align="right" valign="bottom"><a href=
"queuecontrolfile.htm" accesskey="N">Next</a></td>
</tr>
</table>
<hr align="LEFT" width="100%">
</div>
<div class="SECT1">
<h1 class="SECT1"><a name="QUEUELOCKFILE">13.2. Queue Lock
File</a></h1>
<ul>
<li>
<p><var class="LITERAL">spool_lock_file</var><span class=
"emphasis"><i class="EMPHASIS">spool queue lock file -
default %P</i></span></p>
</li>
</ul>
<br>
<br>
<p>When the <b class="APPLICATION">lpd</b> server starts
printing, it will fork individual worker processes to service
each queue. To prevent multiple processes from working on the
same queue, a printer lock file specified by the <var class=
"LITERAL">queue_lock_file</var> option (default <var class=
"LITERAL">%P</var> - the %P is expanded to the print queue
name) is used. In our example, the lock file would be: <tt
class="FILENAME">/var/lpd/pr/pr</tt>.</p>
<p>The process ID of the currently active printer is stored
in the lock file. By reading the lock file and testing to see
if the process is still active, programs such as <b class=
"APPLICATION">lpq</b> can determine queue activity.</p>
<p>Similarly, the worker process may need to create other
processes to assist it. These in turn will create lock or
temporary files in the spool directory as well.</p>
</div>
<div class="NAVFOOTER">
<hr align="LEFT" width="100%">
<table summary="Footer navigation table" width="100%" border=
"0" cellpadding="0" cellspacing="0">
<tr>
<td width="33%" align="left" valign="top"><a href=
"spoolqueue.htm" accesskey="P">Prev</a></td>
<td width="34%" align="center" valign="top"><a href=
"index.htm" accesskey="H">Home</a></td>
<td width="33%" align="right" valign="top"><a href=
"queuecontrolfile.htm" accesskey="N">Next</a></td>
</tr>
<tr>
<td width="33%" align="left" valign="top">Spool Queues
and Files</td>
<td width="34%" align="center" valign="top"><a href=
"spoolqueue.htm" accesskey="U">Up</a></td>
<td width="33%" align="right" valign="top">Spool Control
File</td>
</tr>
</table>
</div>
</body>
</html>
syntax highlighted by Code2HTML, v. 0.9.1