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<H1>CUPS Software Design Description</H1></A><BR>
CUPS-SDD-1.1<BR>
Easy Software Products<BR>
Copyright 1997-2002, All Rights Reserved<BR>
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<HR>
<H1 ALIGN="CENTER"><A NAME="CONTENTS">Table of Contents</A></H1>
<BR>
<BR><B><A HREF="#1">1 Scope</A></B>
<UL>
<LI><A HREF="#1_1">1.1 Identification</A></LI>
<LI><A HREF="#1_2">1.2 System Overview</A></LI>
<LI><A HREF="#1_3">1.3 Document Overview</A></LI>
</UL>
<B><A HREF="#2">2 References</A></B>
<UL>
<LI><A HREF="#2_1">2.1 CUPS Documentation</A></LI>
<LI><A HREF="#2_2">2.2 Other Documents</A></LI>
</UL>
<B><A HREF="#3">3 Design Overview</A></B>
<UL>
<LI><A HREF="#3_1">3.1 Backends</A></LI>
<UL>
<LI><A HREF="#3_1_1">3.1.1 ipp</A></LI>
<LI><A HREF="#3_1_2">3.1.2 lpd</A></LI>
<LI><A HREF="#3_1_3">3.1.3 parallel</A></LI>
<LI><A HREF="#3_1_4">3.1.4 serial</A></LI>
<LI><A HREF="#3_1_5">3.1.5 socket</A></LI>
<LI><A HREF="#3_1_6">3.1.6 usb</A></LI>
</UL>
<LI><A HREF="#3_2">3.2 Berkeley Commands</A></LI>
<UL>
<LI><A HREF="#3_2_1">3.2.1 lpc</A></LI>
<LI><A HREF="#3_2_2">3.2.2 lpq</A></LI>
<LI><A HREF="#3_2_3">3.2.3 lpr</A></LI>
<LI><A HREF="#3_2_4">3.2.4 lprm</A></LI>
</UL>
<LI><A HREF="#3_3">3.3 CGI</A></LI>
<UL>
<LI><A HREF="#3_3_1">3.3.1 admin.cgi</A></LI>
<LI><A HREF="#3_3_2">3.3.2 classes.cgi</A></LI>
<LI><A HREF="#3_3_3">3.3.3 jobs.cgi</A></LI>
<LI><A HREF="#3_3_4">3.3.4 printers.cgi</A></LI>
</UL>
<LI><A HREF="#3_4">3.4 CUPS Application Programmers Interface</A></LI>
<UL>
<LI><A HREF="#3_4_1">3.4.1 Convenience Functions</A></LI>
<LI><A HREF="#3_4_2">3.4.2 HTTP Functions</A></LI>
<LI><A HREF="#3_4_3">3.4.3 IPP Functions</A></LI>
<LI><A HREF="#3_4_4">3.4.4 Language Functions</A></LI>
<LI><A HREF="#3_4_5">3.4.5 PPD Functions</A></LI>
</UL>
<LI><A HREF="#3_5">3.5 CUPS Imaging Library</A></LI>
<UL>
<LI><A HREF="#3_5_1">3.5.1 Colorspace Conversion Functions</A></LI>
<LI><A HREF="#3_5_2">3.5.2 Color Management Functions</A></LI>
<LI><A HREF="#3_5_3">3.5.3 Image Management Functions</A></LI>
<LI><A HREF="#3_5_4">3.5.4 Scaling Functions</A></LI>
<LI><A HREF="#3_5_5">3.5.5 Image File Functions</A></LI>
<LI><A HREF="#3_5_6">3.5.6 Raster Functions</A></LI>
</UL>
<LI><A HREF="#3_6">3.6 Daemons</A></LI>
<UL>
<LI><A HREF="#3_6_1">3.6.1 Line Printer Daemon</A></LI>
<LI><A HREF="#3_6_2">3.6.2 Polling Daemon</A></LI>
</UL>
<LI><A HREF="#3_7">3.7 Filters</A></LI>
<UL>
<LI><A HREF="#3_7_1">3.7.1 hpgltops</A></LI>
<LI><A HREF="#3_7_2">3.7.2 imagetops</A></LI>
<LI><A HREF="#3_7_3">3.7.3 imagetoraster</A></LI>
<LI><A HREF="#3_7_4">3.7.4 pdftops</A></LI>
<LI><A HREF="#3_7_5">3.7.5 pstops</A></LI>
<LI><A HREF="#3_7_6">3.7.6 pstoraster</A></LI>
<LI><A HREF="#3_7_7">3.7.7 rastertoepson</A></LI>
<LI><A HREF="#3_7_8">3.7.8 rastertohp</A></LI>
<LI><A HREF="#3_7_9">3.7.9 texttops</A></LI>
</UL>
<LI><A HREF="#3_8">3.8 Scheduler</A></LI>
<UL>
<LI><A HREF="#3_8_1">3.8.1 Authorization</A></LI>
<LI><A HREF="#3_8_2">3.8.2 Classes</A></LI>
<LI><A HREF="#3_8_3">3.8.3 Client</A></LI>
<LI><A HREF="#3_8_4">3.8.4 Configuration</A></LI>
<LI><A HREF="#3_8_5">3.8.5 Devices</A></LI>
<LI><A HREF="#3_8_6">3.8.6 Directory Services</A></LI>
<LI><A HREF="#3_8_7">3.8.7 IPP</A></LI>
<LI><A HREF="#3_8_8">3.8.8 Jobs</A></LI>
<LI><A HREF="#3_8_9">3.8.9 Logging</A></LI>
<LI><A HREF="#3_8_10">3.8.10 Main</A></LI>
<LI><A HREF="#3_8_11">3.8.11 MIME</A></LI>
<LI><A HREF="#3_8_12">3.8.12 PPDs</A></LI>
<LI><A HREF="#3_8_13">3.8.13 Printers</A></LI>
</UL>
<LI><A HREF="#3_9">3.9 System V Commands</A></LI>
<UL>
<LI><A HREF="#3_9_1">3.9.1 accept</A></LI>
<LI><A HREF="#3_9_2">3.9.2 cancel</A></LI>
<LI><A HREF="#3_9_3">3.9.3 disable</A></LI>
<LI><A HREF="#3_9_4">3.9.4 enable</A></LI>
<LI><A HREF="#3_9_5">3.9.5 lp</A></LI>
<LI><A HREF="#3_9_6">3.9.6 lpadmin</A></LI>
<LI><A HREF="#3_9_7">3.9.7 lpinfo</A></LI>
<LI><A HREF="#3_9_8">3.9.8 lpmove</A></LI>
<LI><A HREF="#3_9_9">3.9.9 lpoptions</A></LI>
<LI><A HREF="#3_9_10">3.9.10 lpstat</A></LI>
<LI><A HREF="#3_9_11">3.9.11 reject</A></LI>
</UL>
</UL>
<B><A HREF="#4">A Glossary</A></B>
<UL>
<LI><A HREF="#4_1">A.1 Terms</A></LI>
<LI><A HREF="#4_2">A.2 Acronyms</A></LI>
</UL>
<HR>
<H1><A NAME="1">1 Scope</A></H1>
<H2><A NAME="1_1">1.1 Identification</A></H2>
 This software design description document provides general information
 on the architecture and coding of the Common UNIX Printing System
 (&quot;CUPS&quot;) Version 1.1.
<H2><A NAME="1_2">1.2 System Overview</A></H2>
<P>CUPS provides a portable printing layer for UNIX&reg;-based operating
 systems. It has been developed by<A HREF="http://www.easysw.com"> Easy
 Software Products</A> to promote a standard printing solution for all
 UNIX vendors and users. CUPS provides the System V and Berkeley
 command-line interfaces.</P>
<P>CUPS uses the Internet Printing Protocol (&quot;IPP&quot;) as the basis for
 managing print jobs and queues. The Line Printer Daemon (&quot;LPD&quot;) Server
 Message Block (&quot;SMB&quot;), and AppSocket (a.k.a. JetDirect) protocols are
 also supported with reduced functionality. CUPS adds network printer
 browsing and PostScript Printer Description (&quot;PPD&quot;) based printing
 options to support real-world printing under UNIX.</P>
<P>CUPS also includes a customized version of GNU Ghostscript (currently
 based off GNU Ghostscript 5.50) and an image file RIP that are used to
 support non-PostScript printers. Sample drivers for HP and EPSON
 printers are included that use these filters.</P>
<H2><A NAME="1_3">1.3 Document Overview</A></H2>
 This software design description document is organized into the
 following sections:
<UL>
<LI>1 - Scope</LI>
<LI>2 - References</LI>
<LI>3 - Design Overview</LI>
<LI>A - Glossary</LI>
</UL>
<H1><A NAME="2">2 References</A></H1>
<H2><A NAME="2_1">2.1 CUPS Documentation</A></H2>
<P>The following CUPS documentation is referenced by this document:</P>
<UL>
<LI>CUPS-CMP-1.1: CUPS Configuration Management Plan</LI>
<LI>CUPS-IDD-1.1: CUPS System Interface Design Description</LI>
<LI>CUPS-IPP-1.1: CUPS Implementation of IPP</LI>
<LI>CUPS-SAM-1.1.x: CUPS Software Administrators Manual</LI>
<LI>CUPS-SDD-1.1: CUPS Software Design Description</LI>
<LI>CUPS-SPM-1.1.x: CUPS Software Programming Manual</LI>
<LI>CUPS-SSR-1.1: CUPS Software Security Report</LI>
<LI>CUPS-STP-1.1: CUPS Software Test Plan</LI>
<LI>CUPS-SUM-1.1.x: CUPS Software Users Manual</LI>
<LI>CUPS-SVD-1.1: CUPS Software Version Description</LI>
</UL>
<H2><A NAME="2_2">2.2 Other Documents</A></H2>
<P>The following non-CUPS documents are referenced by this document:</P>
<UL>
<LI><A HREF="http://partners.adobe.com/asn/developer/PDFS/TN/5003.PPD_Spec_v4.3.pdf">
Adobe PostScript Printer Description File Format Specification, Version
 4.3.</A></LI>
<LI><A HREF="http://partners.adobe.com/asn/developer/PDFS/TN/PLRM.pdf">
Adobe PostScript Language Reference, Third Edition.</A></LI>
<LI>IPP: Job and Printer Set Operations</LI>
<LI>IPP/1.1: Encoding and Transport</LI>
<LI>IPP/1.1: Implementers Guide</LI>
<LI>IPP/1.1: Model and Semantics</LI>
<LI><A HREF="http://www.ietf.org/rfc/rfc1179.txt">RFC 1179, Line Printer
 Daemon Protocol</A></LI>
<LI><A HREF="http://www.ietf.org/rfc/rfc2567.txt">RFC 2567, Design Goals
 for an Internet Printing Protocol</A></LI>
<LI><A HREF="http://www.ietf.org/rfc/rfc2568.txt">RFC 2568, Rationale
 for the Structure of the Model and Protocol</A> for the Internet
 Printing Protocol</LI>
<LI><A HREF="http://www.ietf.org/rfc/rfc2569.txt">RFC 2569, Mapping
 between LPD and IPP Protocols</A></LI>
<LI><A HREF="http://www.ietf.org/rfc/rfc2616.txt">RFC 2616, Hypertext
 Transfer Protocol -- HTTP/1.1</A></LI>
<LI><A HREF="http://www.ietf.org/rfc/rfc2617.txt">RFC 2617, HTTP
 Authentication: Basic and Digest Access</A> Authentication</LI>
</UL>
<H1><A NAME="3">3 Design Overview</A></H1>
 CUPS is composed of 9 software sub-systems that operate together to
 perform common printing tasks:
<UL>
<LI>Backends</LI>
<LI>Berkeley Commands</LI>
<LI>CGI</LI>
<LI>CUPS Application Programmers Interface</LI>
<LI>CUPS Imaging Library</LI>
<LI>Daemons</LI>
<LI>Filters</LI>
<LI>Scheduler</LI>
<LI>System V Commands</LI>
</UL>
<H2><A NAME="3_1">3.1 Backends</A></H2>
 The backends implement communications over a number of different
 interfaces. All backends are called with a common set of arguments:
<UL>
<LI>Device URI - the Uniform Resource Identifier for the output device
 (e.g. <CODE>parallel:/dev/plp</CODE>, <CODE>ipp://hostname/resource</CODE>
).</LI>
<LI>Job Identifier - the job identifier for this job (integer).</LI>
<LI>User Name - the user associated with this job (name string).</LI>
<LI>Title - the title/job-name associated with this job (name string).</LI>
<LI>Copies - the number of copies required (integer).</LI>
<LI>Options - the options associated with this job (space separated
 option strings).</LI>
<LI>Filename (optional) - the file to print; if this option is not
 specified, the backend must read the print file from the standard
 input.</LI>
</UL>
<P>Backends are named using the scheme of the URI, so a URI of
 &quot;ipp://hostname/resource&quot; would be processed by the &quot;ipp&quot; backend.</P>
<H3><A NAME="3_1_1">3.1.1 ipp</A></H3>
<P>The ipp backend sends the specified job to a network printer or host
 using the Internet Printing Protocol. The URI is as specified by the <CODE>
printer-uri-supported</CODE> attribute from the printer or host.</P>
<H3><A NAME="3_1_2">3.1.2 lpd</A></H3>
<P>The lpd backend sends the specified job to a network printer or host
 using the Line Printer Daemon protocol. The URI is of the form:</P>
<UL>
<PRE>lpd://hostname/queue
</PRE>
</UL>
<H3><A NAME="3_1_3">3.1.3 parallel</A></H3>
<P>The parallel backend sends the specified job to a local printer
 connected via the specified parallel port device. The URI is of the
 form:</P>
<UL>
<PRE>parallel:/dev/file
</PRE>
</UL>
<H3><A NAME="3_1_4">3.1.4 serial</A></H3>
<P>The serial backend sends the specified job to a local printer
 connected via the specified serial port device. The URI is of the form:</P>
<UL>
<PRE>serial:/dev/file?option[+option+...]
</PRE>
</UL>
 The options can be any combination of the following:
<UL>
<LI><CODE>baud=<I>rate</I></CODE> - Sets the baud rate for the device.</LI>
<LI><CODE>bits=<I>7 or 8</I></CODE> - Sets the number of data bits.</LI>
<LI><CODE>parity=<I>even</I></CODE> - Sets even parity checking.</LI>
<LI><CODE>parity=<I>odd</I></CODE> - Sets odd parity checking.</LI>
<LI><CODE>parity=<I>none</I></CODE> - Turns parity checking off.</LI>
<LI><CODE>flow=dtrdsr<I></I></CODE> - Turns DTR/DSR (hardware) flow
 control on.</LI>
<LI><CODE>flow=hard<I></I></CODE> - Turns RTS/CTS (hardware) flow
 control on.</LI>
<LI><CODE>flow=none<I></I></CODE> - Turns flow control off.</LI>
<LI><CODE>flow=rtscts<I></I></CODE> - Turns RTS/CTS (hardware) flow
 control on.</LI>
<LI><CODE>flow=xonxoff<I></I></CODE> - Turns XON/XOFF (software) flow
 control on.</LI>
</UL>
<H3><A NAME="3_1_5">3.1.5 socket</A></H3>
<P>The socket backend sends the specified job to a network host using
 the AppSocket protocol commonly used by Hewlett-Packard and Tektronix
 printers. The URI is of the form:</P>
<UL>
<PRE>socket://hostname[:port]
</PRE>
</UL>
 The default port number is 9100.
<H3><A NAME="3_1_6">3.1.6 usb</A></H3>
<P>The usb backend sends the specified job to a local printer connected
 via the specified usb port device. The URI is of the form:</P>
<UL>
<PRE>usb:/dev/file
</PRE>
</UL>
<H2><A NAME="3_2">3.2 Berkeley Commands</A></H2>
<P>The Berkeley commands provide a simple command-line interface to CUPS
 to submit and control print jobs. It is provided for compatibility with
 existing software that is hardcoded to use the Berkeley commands.</P>
<H3><A NAME="3_2_1">3.2.1 lpc</A></H3>
 The lpc command allows users and administrators to check the status and
 control print queues. The version provided with CUPS supports the
 following commands:
<UL>
<LI>quit - Quits the lpc command.</LI>
<LI>status - Shows the status of printers and jobs in the queue.</LI>
</UL>
<H3><A NAME="3_2_2">3.2.2 lpq</A></H3>
<P>The lpq command shows the current queue status.</P>
<H3><A NAME="3_2_3">3.2.3 lpr</A></H3>
<P>The lpr command submits a job for printing. The CUPS version of lpr
 silently ignores the &quot;i&quot;, &quot;t&quot;, &quot;m&quot;, &quot;h&quot;, and &quot;s&quot; options.</P>
<H3><A NAME="3_2_4">3.2.4 lprm</A></H3>
<P>The lprm removes one or more print jobs.</P>
<H2><A NAME="3_3">3.3 CGI</A></H2>
<P>The Common Gateway Interface (CGI) programs provide a web-based
 status interface to monitor the status of printers, classes, and jobs.
 Each of the CGIs utilize HTML template files that can be customized to
 provide alternate appearances.</P>
<H3><A NAME="3_3_1">3.3.1 admin.cgi</A></H3>
<P>The admin CGI provides administration interfaces for printers and
 classes. The user can add, modify, delete, start, stop, and configure
 printers and classes using &quot;wizard&quot; interfaces.</P>
<H3><A NAME="3_3_2">3.3.2 classes.cgi</A></H3>
<P>The classes CGI lists the available printer classes and any pending
 jobs for the class. The user can click on individual classes to limit
 the display and click on jobs to see the job status.</P>
<H3><A NAME="3_3_3">3.3.3 jobs.cgi</A></H3>
<P>The jobs CGI lists the queued print jobs in order of priority. The
 list can be limited by printer or job.</P>
<H3><A NAME="3_3_4">3.3.4 printers.cgi</A></H3>
<P>The printers CGI lists the available printer queues and any pending
 jobs for the printer. The user can click on individual printers to
 limit the display and click on jobs to see the job status.</P>
<H2><A NAME="3_4">3.4 CUPS Application Programmers Interface</A></H2>
<P>The CUPS Application Programmers Interface (&quot;API&quot;) provides common
 convenience, HTTP, IPP, language, and PPD functions used by the CUPS
 software.</P>
<H3><A NAME="3_4_1">3.4.1 Convenience Functions</A></H3>
<P>Convenience functions are provided to submit an IPP request, send a
 print file, cancel a job, get a list of available printers, get a list
 of available classes, get the default printer or class, get the default
 server name, get the local username, and get a password string.</P>
<H3><A NAME="3_4_2">3.4.2 HTTP Functions</A></H3>
<P>The HTTP functions provide functions to connect to HTTP servers,
 issue requests, read data from a server, and write data to a server.</P>
<H3><A NAME="3_4_3">3.4.3 IPP Functions</A></H3>
<P>The IPP function provide functions to manage IPP request data and
 attributes, read IPP responses from a server, and write IPP requests to
 a server.</P>
<H3><A NAME="3_4_4">3.4.4 Language Functions</A></H3>
<P>The language functions provide a standard interface for retrieving
 common textual messages for a particular locale and determining the
 correct encoding (e.g. US ASCII, UTF-8, ISO-8859-1, etc.)</P>
<H3><A NAME="3_4_5">3.4.5 PPD Functions</A></H3>
<P>The PostScript Printer Description functions manage PPD files, select
 options, check for option conflicts, and emit selected options in the
 correct order.</P>
<H2><A NAME="3_5">3.5 CUPS Imaging Library</A></H2>
<P>The CUPS imaging library provides colorspace conversion, color
 management, image management, scaling, image file, and raster functions
 used by the CUPS raster filters.</P>
<H3><A NAME="3_5_1">3.5.1 Colorspace Conversion Functions</A></H3>
<P>The colorspace conversion functions handle conversion of grayscale
 and RGB colors to grayscale, RGB, K, CMY, CMYK, and CMYKcm colorspaces.</P>
<H3><A NAME="3_5_2">3.5.2 Color Management Functions</A></H3>
<P>The color management functions handle gamut mapping and density
 correction. These are integrated with the colorspace conversion
 functions so that colorspace conversion and color management are
 processed in a single step.</P>
<H3><A NAME="3_5_3">3.5.3 Image Management Functions</A></H3>
<P>The image management functions manage a tiled image database that is
 swapped to/from disk as needed.</P>
<H3><A NAME="3_5_4">3.5.4 Scaling Functions</A></H3>
<P>The scaling functions provide image scaling services using
 nearest-neighbor sampling and bilinear interpolation as appropriate.</P>
<H3><A NAME="3_5_5">3.5.5 Image File Functions</A></H3>
<P>The image file functions handle loading of all image file formats.</P>
<H3><A NAME="3_5_6">3.5.6 Raster Functions</A></H3>
<P>The raster functions manage streams of CUPS raster data (described in
 the Interface Design Document) used by non-PostScript printer drivers
 and raster filters.</P>
<H2><A NAME="3_6">3.6 Daemons</A></H2>
<P>The daemons provide additional network functions for the scheduler.
 Currently only two daemons are provided with CUPS.</P>
<H3><A NAME="3_6_1">3.6.1 Line Printer Daemon</A></H3>
<P>The line printer daemon provides remote LPD client support and is run
 by the <CODE>inetd(8)</CODE> daemon as needed.</P>
<H3><A NAME="3_6_2">3.6.2 Polling Daemon</A></H3>
<P>The polling daemon is used to poll a remote server for a list of
 available printers and provide it to the scheduler for addition. A
 separate polling daemon is run by the scheduler for every remote system
 listed for polling in the scheduler configuration file.</P>
<H2><A NAME="3_7">3.7 Filters</A></H2>
<P>The filters implement file conversion services for CUPS. All filters
 are called with a common set of arguments:</P>
<UL>
<LI>Printer name - the name of the destination printer (name string).</LI>
<LI>Job Identifier - the job identifier for this job (integer).</LI>
<LI>User Name - the user associated with this job (name string).</LI>
<LI>Title - the title/job-name associated with this job (name string).</LI>
<LI>Copies - the number of copies required (integer).</LI>
<LI>Options - the options associated with this job (space separated
 option strings).</LI>
<LI>Filename (optional) - the file to print; if this option is not
 specified, the filter must read the input file from the standard input.</LI>
</UL>
<P>Filters are added to the MIME conversion data file and implement all
 necessary conversions from one file type to another.</P>
<H3><A NAME="3_7_1">3.7.1 hpgltops</A></H3>
<P>The hpgltops filter converts HP-GL/2 files into PostScript.</P>
<H3><A NAME="3_7_2">3.7.2 imagetops</A></H3>
<P>The imagetops filter converts image files into PostScript.</P>
<H3><A NAME="3_7_3">3.7.3 imagetoraster</A></H3>
<P>The imagetoraster filter converts image files into CUPS raster data.</P>
<H3><A NAME="3_7_4">3.7.4 pdftops</A></H3>
<P>The pdftops filter converts PDF files into PostScript.</P>
<H3><A NAME="3_7_5">3.7.5 pstops</A></H3>
<P>The pstops filter inserts printer-specific commands from PPD files
 and performs page filtering as requested by the user.</P>
<H3><A NAME="3_7_6">3.7.6 pstoraster</A></H3>
<P>The pstoraster filter converts PostScript program data into CUPS
 raster data.</P>
<H3><A NAME="3_7_7">3.7.7 rastertoepson</A></H3>
<P>The rastertoepson filter handles converting CUPS raster data to ESC/P
 and supports both color and black-and-white printers.</P>
<H3><A NAME="3_7_8">3.7.8 rastertohp</A></H3>
<P>The rastertohp filter handles converting CUPS raster data to HP-PCL
 and supports both color and black-and-white printers.</P>
<H3><A NAME="3_7_9">3.7.9 texttops</A></H3>
<P>The texttops filter converts text files into PostScript.</P>
<H2><A NAME="3_8">3.8 Scheduler</A></H2>
<P>The scheduler is a fully-functional HTTP/1.1 and IPP/1.1 server that
 manages the printers, classes, and jobs in the system. It also handles
 a simple broadcast-based directory service so that remote print queues
 and classes can be accessed transparently from the local system.</P>
<H3><A NAME="3_8_1">3.8.1 Authorization</A></H3>
<P>The authorization module is responsible for performing access control
 and authentication for all HTTP and IPP requests entering the system.</P>
<H3><A NAME="3_8_2">3.8.2 Classes</A></H3>
<P>The classes module is responsible for managing printer classes in the
 system. Each class is a collection of local and/or remote printers. The
 classes module also reads and writes the classes configuration file.</P>
<H3><A NAME="3_8_3">3.8.3 Client</A></H3>
<P>The client module is responsible for all HTTP client communications.
 It handles listening on selected interfaces, accepting connections from
 prospective clients, processing incoming HTTP requests, and sending
 HTTP responses to those requests. The client module also is responsible
 for executing the external CGI programs as needed to support web-based
 printer, class, and job status monitoring and administration.</P>
<P>Once authorized, all IPP requests are sent to the IPP module.</P>
<H3><A NAME="3_8_4">3.8.4 Configuration</A></H3>
<P>The configuration module is responsible for reading the CUPS
 configuration file and initializing the appropriate data structures and
 values. The configuration module also stops CUPS services before
 reading the configuration file and restarts them after the
 configuration file has been read.</P>
<H3><A NAME="3_8_5">3.8.5 Devices</A></H3>
<P>The devices module is responsible for managing the list of available
 devices for the CUPS-Get-Devices operation.</P>
<H3><A NAME="3_8_6">3.8.6 Directory Services</A></H3>
<P>The directory services module sends and recieves printer state
 information over a broadcast socket. Remote printers and classes are
 automatically added to or removed from the local printer and class
 lists as needed.</P>
<P>The directory services module can only recieve printer state
 information over a single UDP port, however it can broadcast to
 multiple addresses and ports as needed.</P>
<H3><A NAME="3_8_7">3.8.7 IPP</A></H3>
<P>The IPP module handles IPP requests and acts accordingly. URI
 validation is also performed here, as a client can post IPP data to any
 URI on the server which might sidestep the access control or
 authentication of the HTTP server.</P>
<H3><A NAME="3_8_8">3.8.8 Jobs</A></H3>
<P>The jobs module manages print jobs, starts filter and backend
 processes for jobs to be printed, and monitors status messages from
 those filters and backends.</P>
<H3><A NAME="3_8_9">3.8.9 Logging</A></H3>
<P>The logging module manages the access, error, and page log files that
 are generated by the scheduler.</P>
<H3><A NAME="3_8_10">3.8.10 Main</A></H3>
<P>The main module is responsible for timing out and dispatching input
 and output for client connections. It also watches for incoming <CODE>
SIGHUP</CODE> and <CODE>SIGCHLD</CODE> signals, reloads the server
 configuration files as needed, and handles child process errors and
 exits.</P>
<H3><A NAME="3_8_11">3.8.11 MIME</A></H3>
<P>The Multimedia Internet Mail Exchange module manages a MIME type and
 conversion database that supports file typing by extension and content
 and least-cost file filtering from a source to a destination file type.</P>
<H3><A NAME="3_8_12">3.8.12 PPDs</A></H3>
<P>The PPDs module is responsible for managing the list of available PPD
 files for the CUPS-Get-PPDs operation.</P>
<H3><A NAME="3_8_13">3.8.13 Printers</A></H3>
<P>The printers module is responsible for managing printers and PPD
 files in the system. The printers module also reads and writes the
 printers configuration file.</P>
<H2><A NAME="3_9">3.9 System V Commands</A></H2>
<P>The System V commands provide a robust command-line interface to CUPS
 to submit and control printers and jobs.</P>
<H3><A NAME="3_9_1">3.9.1 accept</A></H3>
<P>The accept command tells the scheduler to accept new jobs for
 specific printers.</P>
<H3><A NAME="3_9_2">3.9.2 cancel</A></H3>
<P>The cancel command tells the scheduler to cancel one or more jobs
 that are queued for printing.</P>
<H3><A NAME="3_9_3">3.9.3 disable</A></H3>
<P>The disable command tells the scheduler to stop printing jobs on the
 specified printers.</P>
<H3><A NAME="3_9_4">3.9.4 enable</A></H3>
<P>The enable command tells the scheduler to start printing jobs on the
 specified printers.</P>
<H3><A NAME="3_9_5">3.9.5 lp</A></H3>
<P>The lp command submits submits files for printing. Unlike the
 standard System V lp command, a single CUPS lp command will generate a
 separate job ID for each file that is printed. Also, the Solaris &quot;f&quot;,
 &quot;H&quot;, &quot;P&quot;, &quot;S&quot;, and &quot;y&quot; options are silently ignored.</P>
<H3><A NAME="3_9_6">3.9.6 lpadmin</A></H3>
<P>The lpadmin command manages printer queues and classes. The Solaris
 &quot;A&quot;, &quot;F&quot;, &quot;I&quot;, &quot;M&quot;, &quot;P&quot;, &quot;Q&quot;, &quot;S&quot;, &quot;T&quot;, &quot;U&quot;, &quot;W&quot;, &quot;f&quot;, &quot;l&quot;, &quot;m&quot;, &quot;o&quot;,
 &quot;s&quot;, &quot;t&quot;, and &quot;u&quot; options are not supported, and new options &quot;P&quot; (PPD
 file) and &quot;E&quot; (enable and accept) are provided to configure
 CUPS-specific features.</P>
<H3><A NAME="3_9_7">3.9.7 lpinfo</A></H3>
<P>The lpinfo command lists the available PPD files or devices as
 selected by the user.</P>
<H3><A NAME="3_9_8">3.9.8 lpmove</A></H3>
<P>The lpmove command moves a print job to a new destination.</P>
<H3><A NAME="3_9_9">3.9.9 lpoptions</A></H3>
<P>The lpoptions command manages user-defined printers and options.</P>
<H3><A NAME="3_9_10">3.9.10 lpstat</A></H3>
<P>The lpstat command lists printers, classes, and jobs as requested by
 the user.</P>
<H3><A NAME="3_9_11">3.9.11 reject</A></H3>
<P>The reject command tells the scheduler not to accept new jobs for
 specific printers.</P>
<H1 TYPE="A" VALUE="1"><A NAME="4">A Glossary</A></H1>
<H2><A NAME="4_1">A.1 Terms</A></H2>
<DL>
<DT>C</DT>
<DD>A computer language.</DD>
<DT>parallel</DT>
<DD>Sending or receiving data more than 1 bit at a time.</DD>
<DT>pipe</DT>
<DD>A one-way communications channel between two programs.</DD>
<DT>serial</DT>
<DD>Sending or receiving data 1 bit at a time.</DD>
<DT>socket</DT>
<DD>A two-way network communications channel.</DD>
</DL>
<H2><A NAME="4_2">A.2 Acronyms</A></H2>
<DL>
<DT>ASCII</DT>
<DD>American Standard Code for Information Interchange</DD>
<DT>CUPS</DT>
<DD>Common UNIX Printing System</DD>
<DT>ESC/P</DT>
<DD>EPSON Standard Code for Printers</DD>
<DT>FTP</DT>
<DD>File Transfer Protocol</DD>
<DT>HP-GL</DT>
<DD>Hewlett-Packard Graphics Language</DD>
<DT>HP-PCL</DT>
<DD>Hewlett-Packard Page Control Language</DD>
<DT>HP-PJL</DT>
<DD>Hewlett-Packard Printer Job Language</DD>
<DT>IETF</DT>
<DD>Internet Engineering Task Force</DD>
<DT>IPP</DT>
<DD>Internet Printing Protocol</DD>
<DT>ISO</DT>
<DD>International Standards Organization</DD>
<DT>LPD</DT>
<DD>Line Printer Daemon</DD>
<DT>MIME</DT>
<DD>Multimedia Internet Mail Exchange</DD>
<DT>PPD</DT>
<DD>PostScript Printer Description</DD>
<DT>SMB</DT>
<DD>Server Message Block</DD>
<DT>TFTP</DT>
<DD>Trivial File Transfer Protocol</DD>
</DL>
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