1<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> 2 3<html> 4 <head> 5 <meta name="generator" content="HTML Tidy, see www.w3.org"> 6 <title>LPRng Supported Filters</title> 7 <meta name="GENERATOR" content= 8 "Modular DocBook HTML Stylesheet Version 1.7"> 9 <link rel="HOME" title=" LPRng Reference Manual" href= 10 "index.htm"> 11 <link rel="UP" title="Filters " href="filters.htm"> 12 <link rel="PREVIOUS" title= 13 "Filter Command Line Options and Environment Variables " href= 14 "filteroptions.htm"> 15 <link rel="NEXT" title="lpf " href="lpf.htm"> 16 </head> 17 18 <body class="SECT1" bgcolor="#FFFFFF" text="#000000" link= 19 "#0000FF" vlink="#840084" alink="#0000FF"> 20 <div class="NAVHEADER"> 21 <table summary="Header navigation table" width="100%" border= 22 "0" cellpadding="0" cellspacing="0"> 23 <tr> 24 <th colspan="3" align="center">LPRng Reference Manual: 5 25 Sep 2003 (For LPRng-3.8.22)</th> 26 </tr> 27 28 <tr> 29 <td width="10%" align="left" valign="bottom"><a href= 30 "filteroptions.htm" accesskey="P">Prev</a></td> 31 32 <td width="80%" align="center" valign="bottom">Chapter 33 16. Filters</td> 34 35 <td width="10%" align="right" valign="bottom"><a href= 36 "lpf.htm" accesskey="N">Next</a></td> 37 </tr> 38 </table> 39 <hr align="LEFT" width="100%"> 40 </div> 41 42 <div class="SECT1"> 43 <h1 class="SECT1"><a name="AEN8397">16.9. <b class= 44 "APPLICATION">LPRng</b> Supported Filters</a></h1> 45 46 <p>There already exists a large library of ready-to-use 47 filters. Some of them have <b class= 48 "APPLICATION">LPRng</b>-specific versions, which can be found 49 at the <a href="secftp.htm"><b class="APPLICATION">LPRng</b> 50 ftp mirror sites</a>.</p> 51 52 <div class="SECT2"> 53 <h2 class="SECT2"><a name="AEN8404">16.9.1. Filter Support 54 Conventions</a></h2> 55 56 <p>By convention, most filters are either totally 57 standalone (very rare) or require a set of support files or 58 configuration files. There are two types of configuration 59 files: per print queue configuration information and global 60 configuration information.</p> 61 62 <p>Since a print filter executes with the spool queue 63 directory as the current directory, most filters put per 64 print queue configuration information in a file in the 65 spool directory. Some <span class="emphasis"><i class= 66 "EMPHASIS">vintage</i></span> filters insist on having 67 these files <span class="emphasis"><i class= 68 "EMPHASIS">hidden</i></span> with names such as <span 69 class="emphasis"><i class="EMPHASIS"><tt class= 70 "FILENAME">.setup</tt></i></span>. This can make it 71 difficult for administrators to determine where the 72 configuration files are.</p> 73 74 <p>Global configuration files are usually placed in 75 commonly accessible directories such as <span class= 76 "emphasis"><i class="EMPHASIS"><tt class= 77 "FILENAME">/usr/local/libexec/filters</tt></i></span> and 78 its subdirectories. This allows the <b class= 79 "APPLICATION">LPRng</b> administrator to set the privileges 80 on these directories such that only the <b class= 81 "APPLICATION">lpd</b> process can access them.</p> 82 83 <p>When a filter is invoked, it is passed a large number of 84 options, many of which are totally ignored in filter 85 operation. However, for many purposes it is necessary to 86 provide options to the filters to tailor their operation to 87 the particular spool queue needs.</p> 88 89 <p>An alternative to using information in a file is to 90 place options in the printcap entry and have the filter 91 extract them from the <var class= 92 "ENVAR">PRINTCAP_ENTRY</var> environment variable value. 93 This is much easier to implement, but is specific to <b 94 class="APPLICATION">LPRng</b>.</p> 95 </div> 96 </div> 97 98 <div class="NAVFOOTER"> 99 <hr align="LEFT" width="100%"> 100 101 <table summary="Footer navigation table" width="100%" border= 102 "0" cellpadding="0" cellspacing="0"> 103 <tr> 104 <td width="33%" align="left" valign="top"><a href= 105 "filteroptions.htm" accesskey="P">Prev</a></td> 106 107 <td width="34%" align="center" valign="top"><a href= 108 "index.htm" accesskey="H">Home</a></td> 109 110 <td width="33%" align="right" valign="top"><a href= 111 "lpf.htm" accesskey="N">Next</a></td> 112 </tr> 113 114 <tr> 115 <td width="33%" align="left" valign="top">Filter Command 116 Line Options and Environment Variables</td> 117 118 <td width="34%" align="center" valign="top"><a href= 119 "filters.htm" accesskey="U">Up</a></td> 120 121 <td width="33%" align="right" valign="top">lpf</td> 122 </tr> 123 </table> 124 </div> 125 </body> 126</html> 127 128