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>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="PREVIOUS" title="Debugging " href="debugging.htm"> 12 <link rel="NEXT" title="Filter Exit Codes " href= 13 "exitcodes.htm"> 14 </head> 15 16 <body class="CHAPTER" bgcolor="#FFFFFF" text="#000000" link= 17 "#0000FF" vlink="#840084" alink="#0000FF"> 18 <div class="NAVHEADER"> 19 <table summary="Header navigation table" width="100%" border= 20 "0" cellpadding="0" cellspacing="0"> 21 <tr> 22 <th colspan="3" align="center">LPRng Reference Manual: 5 23 Sep 2003 (For LPRng-3.8.22)</th> 24 </tr> 25 26 <tr> 27 <td width="10%" align="left" valign="bottom"><a href= 28 "debugging.htm" accesskey="P">Prev</a></td> 29 30 <td width="80%" align="center" valign="bottom"> 31 </td> 32 33 <td width="10%" align="right" valign="bottom"><a href= 34 "exitcodes.htm" accesskey="N">Next</a></td> 35 </tr> 36 </table> 37 <hr align="LEFT" width="100%"> 38 </div> 39 40 <div class="CHAPTER"> 41 <h1><a name="FILTERS"></a>Chapter 16. Filters</h1> 42 43 <div class="TOC"> 44 <dl> 45 <dt><b>Table of Contents</b></dt> 46 47 <dt>16.1. <a href="filters.htm#AEN7758">Filter 48 Functions</a></dt> 49 50 <dt>16.2. <a href="exitcodes.htm">Filter Exit 51 Codes</a></dt> 52 53 <dt>16.3. <a href="printjobformats.htm">Print Job 54 Formats</a></dt> 55 56 <dt>16.4. <a href="ofdetails.htm">OF Filter</a></dt> 57 58 <dt>16.5. <a href="pr.htm"><b class="APPLICATION">lpr</b> 59 -p format</a></dt> 60 61 <dt>16.6. <a href="x7980.htm"><b class= 62 "APPLICATION">lpr</b> binary (-l) format</a></dt> 63 64 <dt>16.7. <a href="chainingfilters.htm">Chaining 65 Filters</a></dt> 66 67 <dt>16.8. <a href="filteroptions.htm">Filter Command Line 68 Options and Environment Variables</a></dt> 69 70 <dt>16.9. <a href="x8397.htm"><b class= 71 "APPLICATION">LPRng</b> Supported Filters</a></dt> 72 73 <dt>16.10. <a href="lpf.htm">lpf</a></dt> 74 75 <dt>16.11. <a href="ifhp.htm"><b class= 76 "APPLICATION">ifhp</b> Filter</a></dt> 77 </dl> 78 </div> 79 80 <p>This section gives an overview of how <b class= 81 "APPLICATION">LPRng</b> uses filter programs, and gives a 82 detailed discussion of how the printcap options and filters 83 interact.</p> 84 85 <div class="SECT1"> 86 <h1 class="SECT1"><a name="AEN7758">16.1. Filter 87 Functions</a></h1> 88 89 <p>Print filters are one of the most powerful tools in 90 BSD-style printer systems.</p> 91 92 <p>In general UNIX terms, a <span class="emphasis"><i 93 class="EMPHASIS">filter</i></span> is a program that takes 94 its input file(s), does something with it, and sends the 95 result to its standard output. Most UNIX utilities are 96 designed as filters. (But since you are a system manager, 97 you should already know that :))</p> 98 99 <p>In the context of a BSD-style print spooler (and also <b 100 class="APPLICATION">LPRng</b>), the term <span class= 101 "emphasis"><i class="EMPHASIS">filter</i></span> refers to 102 a program that processes file while it is being transferred 103 to a printer.</p> 104 105 <p>The filter is executed with <acronym class= 106 "ACRONYM">STDIN</acronym> reading from the file to be 107 printed <acronym class="ACRONYM">STDOUT</acronym> to the 108 printer device or a temporary file. <acronym class= 109 "ACRONYM">STDERR</acronym> (file handle 2) is redirected to 110 the status file, and file handle3 to an accounting file or 111 program.</p> 112 113 <p>A filter can be as simple as a <acronym class= 114 "ACRONYM">LF</acronym> to <tt class="FILENAME">CR/LF</tt> 115 translator, or it can incorporate a complete accounting 116 system, automatic file type translations, or even redirect 117 the job to another printing system.</p> 118 119 <p>The <b class="APPLICATION">lpf</b> filter supplied as 120 part of the <b class="APPLICATION">LPRng</b> distribution 121 is a a very simple CR to CR/LF conversion filter. The <b 122 class="APPLICATION">ifhp</b> filter provides support for 123 more complex PostScript, PCL, and text printers.</p> 124 </div> 125 </div> 126 127 <div class="NAVFOOTER"> 128 <hr align="LEFT" width="100%"> 129 130 <table summary="Footer navigation table" width="100%" border= 131 "0" cellpadding="0" cellspacing="0"> 132 <tr> 133 <td width="33%" align="left" valign="top"><a href= 134 "debugging.htm" accesskey="P">Prev</a></td> 135 136 <td width="34%" align="center" valign="top"><a href= 137 "index.htm" accesskey="H">Home</a></td> 138 139 <td width="33%" align="right" valign="top"><a href= 140 "exitcodes.htm" accesskey="N">Next</a></td> 141 </tr> 142 143 <tr> 144 <td width="33%" align="left" valign="top">Debugging</td> 145 146 <td width="34%" align="center" valign="top"> </td> 147 148 <td width="33%" align="right" valign="top">Filter Exit 149 Codes</td> 150 </tr> 151 </table> 152 </div> 153 </body> 154</html> 155 156