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  23 <CENTER><A HREF="#CONTENTS"><IMG SRC="images/cups-large.gif" BORDER="0" WIDTH="431" HEIGHT="511"><BR>
  24 <H1>CUPS Software Design Description</H1></A><BR>
  25 CUPS-SDD-1.2<BR>
  26 Easy Software Products<BR>
  27 Copyright 1997-2003, All Rights Reserved<BR>
  28 </CENTER>
  29 <HR>
  30 <H1 ALIGN="CENTER"><A NAME="CONTENTS">Table of Contents</A></H1>
  31 <BR>
  32 <BR><B><A HREF="#1">1 Scope</A></B>
  33 <UL>
  34 <LI><A HREF="#1_1">1.1 Identification</A></LI>
  35 <LI><A HREF="#1_2">1.2 System Overview</A></LI>
  36 <LI><A HREF="#1_3">1.3 Document Overview</A></LI>
  37 </UL>
  38 <B><A HREF="#2">2 References</A></B>
  39 <UL>
  40 <LI><A HREF="#2_1">2.1 CUPS Documentation</A></LI>
  41 <LI><A HREF="#2_2">2.2 Other Documents</A></LI>
  42 </UL>
  43 <B><A HREF="#3">3 Design Overview</A></B>
  44 <UL>
  45 <LI><A HREF="#3_1">3.1 Backends</A></LI>
  46 <UL>
  47 <LI><A HREF="#3_1_1">3.1.1 ipp</A></LI>
  48 <LI><A HREF="#3_1_2">3.1.2 lpd</A></LI>
  49 <LI><A HREF="#3_1_3">3.1.3 parallel</A></LI>
  50 <LI><A HREF="#3_1_4">3.1.4 serial</A></LI>
  51 <LI><A HREF="#3_1_5">3.1.5 socket</A></LI>
  52 <LI><A HREF="#3_1_6">3.1.6 usb</A></LI>
  53 </UL>
  54 <LI><A HREF="#3_2">3.2 Berkeley Commands</A></LI>
  55 <UL>
  56 <LI><A HREF="#3_2_1">3.2.1 lpc</A></LI>
  57 <LI><A HREF="#3_2_2">3.2.2 lpq</A></LI>
  58 <LI><A HREF="#3_2_3">3.2.3 lpr</A></LI>
  59 <LI><A HREF="#3_2_4">3.2.4 lprm</A></LI>
  60 </UL>
  61 <LI><A HREF="#3_3">3.3 CGI</A></LI>
  62 <UL>
  63 <LI><A HREF="#3_3_1">3.3.1 admin.cgi</A></LI>
  64 <LI><A HREF="#3_3_2">3.3.2 classes.cgi</A></LI>
  65 <LI><A HREF="#3_3_3">3.3.3 jobs.cgi</A></LI>
  66 <LI><A HREF="#3_3_4">3.3.4 printers.cgi</A></LI>
  67 </UL>
  68 <LI><A HREF="#3_4">3.4 CUPS Application Programmers Interface</A></LI>
  69 <UL>
  70 <LI><A HREF="#3_4_1">3.4.1 Convenience Functions</A></LI>
  71 <LI><A HREF="#3_4_2">3.4.2 HTTP Functions</A></LI>
  72 <LI><A HREF="#3_4_3">3.4.3 IPP Functions</A></LI>
  73 <LI><A HREF="#3_4_4">3.4.4 Language Functions</A></LI>
  74 <LI><A HREF="#3_4_5">3.4.5 PPD Functions</A></LI>
  75 </UL>
  76 <LI><A HREF="#3_5">3.5 CUPS Imaging Library</A></LI>
  77 <UL>
  78 <LI><A HREF="#3_5_1">3.5.1 Colorspace Conversion Functions</A></LI>
  79 <LI><A HREF="#3_5_2">3.5.2 Color Management Functions</A></LI>
  80 <LI><A HREF="#3_5_3">3.5.3 Image Management Functions</A></LI>
  81 <LI><A HREF="#3_5_4">3.5.4 Scaling Functions</A></LI>
  82 <LI><A HREF="#3_5_5">3.5.5 Image File Functions</A></LI>
  83 <LI><A HREF="#3_5_6">3.5.6 Raster Functions</A></LI>
  84 </UL>
  85 <LI><A HREF="#3_6">3.6 Daemons</A></LI>
  86 <UL>
  87 <LI><A HREF="#3_6_1">3.6.1 Line Printer Daemon</A></LI>
  88 <LI><A HREF="#3_6_2">3.6.2 Polling Daemon</A></LI>
  89 </UL>
  90 <LI><A HREF="#3_7">3.7 Filters</A></LI>
  91 <UL>
  92 <LI><A HREF="#3_7_1">3.7.1 hpgltops</A></LI>
  93 <LI><A HREF="#3_7_2">3.7.2 imagetops</A></LI>
  94 <LI><A HREF="#3_7_3">3.7.3 imagetoraster</A></LI>
  95 <LI><A HREF="#3_7_4">3.7.4 pdftops</A></LI>
  96 <LI><A HREF="#3_7_5">3.7.5 pstops</A></LI>
  97 <LI><A HREF="#3_7_6">3.7.6 pstoraster</A></LI>
  98 <LI><A HREF="#3_7_7">3.7.7 rastertoepson</A></LI>
  99 <LI><A HREF="#3_7_8">3.7.8 rastertohp</A></LI>
 100 <LI><A HREF="#3_7_9">3.7.9 texttops</A></LI>
 101 </UL>
 102 <LI><A HREF="#3_8">3.8 Scheduler</A></LI>
 103 <UL>
 104 <LI><A HREF="#3_8_1">3.8.1 Authorization</A></LI>
 105 <LI><A HREF="#3_8_2">3.8.2 Classes</A></LI>
 106 <LI><A HREF="#3_8_3">3.8.3 Client</A></LI>
 107 <LI><A HREF="#3_8_4">3.8.4 Configuration</A></LI>
 108 <LI><A HREF="#3_8_5">3.8.5 Devices</A></LI>
 109 <LI><A HREF="#3_8_6">3.8.6 Directory Services</A></LI>
 110 <LI><A HREF="#3_8_7">3.8.7 IPP</A></LI>
 111 <LI><A HREF="#3_8_8">3.8.8 Jobs</A></LI>
 112 <LI><A HREF="#3_8_9">3.8.9 Logging</A></LI>
 113 <LI><A HREF="#3_8_10">3.8.10 Main</A></LI>
 114 <LI><A HREF="#3_8_11">3.8.11 MIME</A></LI>
 115 <LI><A HREF="#3_8_12">3.8.12 PPDs</A></LI>
 116 <LI><A HREF="#3_8_13">3.8.13 Printers</A></LI>
 117 </UL>
 118 <LI><A HREF="#3_9">3.9 System V Commands</A></LI>
 119 <UL>
 120 <LI><A HREF="#3_9_1">3.9.1 accept</A></LI>
 121 <LI><A HREF="#3_9_2">3.9.2 cancel</A></LI>
 122 <LI><A HREF="#3_9_3">3.9.3 disable</A></LI>
 123 <LI><A HREF="#3_9_4">3.9.4 enable</A></LI>
 124 <LI><A HREF="#3_9_5">3.9.5 lp</A></LI>
 125 <LI><A HREF="#3_9_6">3.9.6 lpadmin</A></LI>
 126 <LI><A HREF="#3_9_7">3.9.7 lpinfo</A></LI>
 127 <LI><A HREF="#3_9_8">3.9.8 lpmove</A></LI>
 128 <LI><A HREF="#3_9_9">3.9.9 lpoptions</A></LI>
 129 <LI><A HREF="#3_9_10">3.9.10 lpstat</A></LI>
 130 <LI><A HREF="#3_9_11">3.9.11 reject</A></LI>
 131 </UL>
 132 </UL>
 133 <B><A HREF="#4">A Glossary</A></B>
 134 <UL>
 135 <LI><A HREF="#4_1">A.1 Terms</A></LI>
 136 <LI><A HREF="#4_2">A.2 Acronyms</A></LI>
 137 </UL>
 138 <HR>
 139 <H1><A NAME="1">1 Scope</A></H1>
 140 <H2><A NAME="1_1">1.1 Identification</A></H2>
 141  This software design description document provides general information
 142  on the architecture and coding of the Common UNIX Printing System
 143  (&quot;CUPS&quot;) Version 1.2.
 144 <H2><A NAME="1_2">1.2 System Overview</A></H2>
 145 <P>CUPS provides a portable printing layer for UNIX&reg;-based operating
 146  systems. It has been developed by<A HREF="http://www.easysw.com"> Easy
 147  Software Products</A> to promote a standard printing solution for all
 148  UNIX vendors and users. CUPS provides the System V and Berkeley
 149  command-line interfaces.</P>
 150 <P>CUPS uses the Internet Printing Protocol (&quot;IPP&quot;) as the basis for
 151  managing print jobs and queues. The Line Printer Daemon (&quot;LPD&quot;) Server
 152  Message Block (&quot;SMB&quot;), and AppSocket (a.k.a. JetDirect) protocols are
 153  also supported with reduced functionality. CUPS adds network printer
 154  browsing and PostScript Printer Description (&quot;PPD&quot;) based printing
 155  options to support real-world printing under UNIX.</P>
 156 <P>CUPS also includes a customized version of GNU Ghostscript (currently
 157  based off GNU Ghostscript 5.50) and an image file RIP that are used to
 158  support non-PostScript printers. Sample drivers for HP and EPSON
 159  printers are included that use these filters.</P>
 160 <H2><A NAME="1_3">1.3 Document Overview</A></H2>
 161  This software design description document is organized into the
 162  following sections:
 163 <UL>
 164 <LI>1 - Scope</LI>
 165 <LI>2 - References</LI>
 166 <LI>3 - Design Overview</LI>
 167 <LI>A - Glossary</LI>
 168 </UL>
 169 <H1><A NAME="2">2 References</A></H1>
 170 <H2><A NAME="2_1">2.1 CUPS Documentation</A></H2>
 171 <P>The following CUPS documentation is referenced by this document:</P>
 172 <UL>
 173 <LI>CUPS-CMP-1.2: CUPS Configuration Management Plan</LI>
 174 <LI>CUPS-IDD-1.2: CUPS System Interface Design Description</LI>
 175 <LI>CUPS-IPP-1.2: CUPS Implementation of IPP</LI>
 176 <LI>CUPS-SAM-1.2.x: CUPS Software Administrators Manual</LI>
 177 <LI>CUPS-SDD-1.2: CUPS Software Design Description</LI>
 178 <LI>CUPS-SPM-1.2.x: CUPS Software Programming Manual</LI>
 179 <LI>CUPS-SSR-1.2: CUPS Software Security Report</LI>
 180 <LI>CUPS-STP-1.2: CUPS Software Test Plan</LI>
 181 <LI>CUPS-SUM-1.2.x: CUPS Software Users Manual</LI>
 182 <LI>CUPS-SVD-1.2: CUPS Software Version Description</LI>
 183 </UL>
 184 <H2><A NAME="2_2">2.2 Other Documents</A></H2>
 185 <P>The following non-CUPS documents are referenced by this document:</P>
 186 <UL>
 187 <LI><A HREF="http://partners.adobe.com/asn/developer/PDFS/TN/5003.PPD_Spec_v4.3.pdf">
 188 Adobe PostScript Printer Description File Format Specification, Version
 189  4.3.</A></LI>
 190 <LI><A HREF="http://partners.adobe.com/asn/developer/PDFS/TN/PLRM.pdf">
 191 Adobe PostScript Language Reference, Third Edition.</A></LI>
 192 <LI>IPP: Job and Printer Set Operations</LI>
 193 <LI>IPP/1.1: Encoding and Transport</LI>
 194 <LI>IPP/1.1: Implementers Guide</LI>
 195 <LI>IPP/1.1: Model and Semantics</LI>
 196 <LI><A HREF="http://www.ietf.org/rfc/rfc1179.txt">RFC 1179, Line Printer
 197  Daemon Protocol</A></LI>
 198 <LI><A HREF="http://www.ietf.org/rfc/rfc2567.txt">RFC 2567, Design Goals
 199  for an Internet Printing Protocol</A></LI>
 200 <LI><A HREF="http://www.ietf.org/rfc/rfc2568.txt">RFC 2568, Rationale
 201  for the Structure of the Model and Protocol for the Internet Printing
 202  Protocol</A></LI>
 203 <LI><A HREF="http://www.ietf.org/rfc/rfc2569.txt">RFC 2569, Mapping
 204  between LPD and IPP Protocols</A></LI>
 205 <LI><A HREF="http://www.ietf.org/rfc/rfc2616.txt">RFC 2616, Hypertext
 206  Transfer Protocol -- HTTP/1.1</A></LI>
 207 <LI><A HREF="http://www.ietf.org/rfc/rfc2617.txt">RFC 2617, HTTP
 208  Authentication: Basic and Digest Access</A> Authentication</LI>
 209 </UL>
 210 <H1><A NAME="3">3 Design Overview</A></H1>
 211  CUPS is composed of 9 software sub-systems that operate together to
 212  perform common printing tasks:
 213 <UL>
 214 <LI>Backends</LI>
 215 <LI>Berkeley Commands</LI>
 216 <LI>CGI</LI>
 217 <LI>CUPS Application Programmers Interface</LI>
 218 <LI>CUPS Imaging Library</LI>
 219 <LI>Daemons</LI>
 220 <LI>Filters</LI>
 221 <LI>Scheduler</LI>
 222 <LI>System V Commands</LI>
 223 </UL>
 224 <H2><A NAME="3_1">3.1 Backends</A></H2>
 225  The backends implement communications over a number of different
 226  interfaces. All backends are called with a common set of arguments:
 227 <UL>
 228 <LI>Device URI - the Uniform Resource Identifier for the output device
 229  (e.g. <CODE>parallel:/dev/plp</CODE>, <CODE>ipp://hostname/resource</CODE>
 230 ).</LI>
 231 <LI>Job Identifier - the job identifier for this job (integer).</LI>
 232 <LI>User Name - the user associated with this job (name string).</LI>
 233 <LI>Title - the title/job-name associated with this job (name string).</LI>
 234 <LI>Copies - the number of copies required (integer).</LI>
 235 <LI>Options - the options associated with this job (space separated
 236  option strings).</LI>
 237 <LI>Filename (optional) - the file to print; if this option is not
 238  specified, the backend must read the print file from the standard
 239  input.</LI>
 240 </UL>
 241 <P>Backends are named using the scheme of the URI, so a URI of
 242  &quot;ipp://hostname/resource&quot; would be processed by the &quot;ipp&quot; backend.</P>
 243 <H3><A NAME="3_1_1">3.1.1 ipp</A></H3>
 244 <P>The ipp backend sends the specified job to a network printer or host
 245  using the Internet Printing Protocol. The URI is as specified by the <CODE>
 246 printer-uri-supported</CODE> attribute from the printer or host.</P>
 247 <H3><A NAME="3_1_2">3.1.2 lpd</A></H3>
 248 <P>The lpd backend sends the specified job to a network printer or host
 249  using the Line Printer Daemon protocol. The URI is of the form:</P>
 250 <UL>
 251 <PRE>lpd://hostname/queue
 252 </PRE>
 253 </UL>
 254 <H3><A NAME="3_1_3">3.1.3 parallel</A></H3>
 255 <P>The parallel backend sends the specified job to a local printer
 256  connected via the specified parallel port device. The URI is of the
 257  form:</P>
 258 <UL>
 259 <PRE>parallel:/dev/file
 260 </PRE>
 261 </UL>
 262 <H3><A NAME="3_1_4">3.1.4 serial</A></H3>
 263 <P>The serial backend sends the specified job to a local printer
 264  connected via the specified serial port device. The URI is of the form:</P>
 265 <UL>
 266 <PRE>serial:/dev/file?option[+option+...]
 267 </PRE>
 268 </UL>
 269  The options can be any combination of the following:
 270 <UL>
 271 <LI><CODE>baud=<I>rate</I></CODE> - Sets the baud rate for the device.</LI>
 272 <LI><CODE>bits=<I>7 or 8</I></CODE> - Sets the number of data bits.</LI>
 273 <LI><CODE>parity=<I>even</I></CODE> - Sets even parity checking.</LI>
 274 <LI><CODE>parity=<I>odd</I></CODE> - Sets odd parity checking.</LI>
 275 <LI><CODE>parity=<I>none</I></CODE> - Turns parity checking off.</LI>
 276 <LI><CODE>flow=dtrdsr<I></I></CODE> - Turns DTR/DSR (hardware) flow
 277  control on.</LI>
 278 <LI><CODE>flow=hard<I></I></CODE> - Turns RTS/CTS (hardware) flow
 279  control on.</LI>
 280 <LI><CODE>flow=none<I></I></CODE> - Turns flow control off.</LI>
 281 <LI><CODE>flow=rtscts<I></I></CODE> - Turns RTS/CTS (hardware) flow
 282  control on.</LI>
 283 <LI><CODE>flow=xonxoff<I></I></CODE> - Turns XON/XOFF (software) flow
 284  control on.</LI>
 285 </UL>
 286 <H3><A NAME="3_1_5">3.1.5 socket</A></H3>
 287 <P>The socket backend sends the specified job to a network host using
 288  the AppSocket protocol commonly used by Hewlett-Packard and Tektronix
 289  printers. The URI is of the form:</P>
 290 <UL>
 291 <PRE>socket://hostname[:port]
 292 </PRE>
 293 </UL>
 294  The default port number is 9100.
 295 <H3><A NAME="3_1_6">3.1.6 usb</A></H3>
 296 <P>The usb backend sends the specified job to a local printer connected
 297  via the specified usb port device. The URI is of the form:</P>
 298 <UL>
 299 <PRE>usb:/dev/file
 300 </PRE>
 301 </UL>
 302 <H2><A NAME="3_2">3.2 Berkeley Commands</A></H2>
 303 <P>The Berkeley commands provide a simple command-line interface to CUPS
 304  to submit and control print jobs. It is provided for compatibility with
 305  existing software that is hardcoded to use the Berkeley commands.</P>
 306 <H3><A NAME="3_2_1">3.2.1 lpc</A></H3>
 307  The lpc command allows users and administrators to check the status and
 308  control print queues. The version provided with CUPS supports the
 309  following commands:
 310 <UL>
 311 <LI>quit - Quits the lpc command.</LI>
 312 <LI>status - Shows the status of printers and jobs in the queue.</LI>
 313 </UL>
 314 <H3><A NAME="3_2_2">3.2.2 lpq</A></H3>
 315 <P>The lpq command shows the current queue status.</P>
 316 <H3><A NAME="3_2_3">3.2.3 lpr</A></H3>
 317 <P>The lpr command submits a job for printing. The CUPS version of lpr
 318  silently ignores the &quot;i&quot;, &quot;t&quot;, &quot;m&quot;, &quot;h&quot;, and &quot;s&quot; options.</P>
 319 <H3><A NAME="3_2_4">3.2.4 lprm</A></H3>
 320 <P>The lprm removes one or more print jobs.</P>
 321 <H2><A NAME="3_3">3.3 CGI</A></H2>
 322 <P>The Common Gateway Interface (CGI) programs provide a web-based
 323  status interface to monitor the status of printers, classes, and jobs.
 324  Each of the CGIs utilize HTML template files that can be customized to
 325  provide alternate appearances.</P>
 326 <H3><A NAME="3_3_1">3.3.1 admin.cgi</A></H3>
 327 <P>The admin CGI provides administration interfaces for printers and
 328  classes. The user can add, modify, delete, start, stop, and configure
 329  printers and classes using &quot;wizard&quot; interfaces.</P>
 330 <H3><A NAME="3_3_2">3.3.2 classes.cgi</A></H3>
 331 <P>The classes CGI lists the available printer classes and any pending
 332  jobs for the class. The user can click on individual classes to limit
 333  the display and click on jobs to see the job status.</P>
 334 <H3><A NAME="3_3_3">3.3.3 jobs.cgi</A></H3>
 335 <P>The jobs CGI lists the queued print jobs in order of priority. The
 336  list can be limited by printer or job.</P>
 337 <H3><A NAME="3_3_4">3.3.4 printers.cgi</A></H3>
 338 <P>The printers CGI lists the available printer queues and any pending
 339  jobs for the printer. The user can click on individual printers to
 340  limit the display and click on jobs to see the job status.</P>
 341 <H2><A NAME="3_4">3.4 CUPS Application Programmers Interface</A></H2>
 342 <P>The CUPS Application Programmers Interface (&quot;API&quot;) provides common
 343  convenience, HTTP, IPP, language, and PPD functions used by the CUPS
 344  software.</P>
 345 <H3><A NAME="3_4_1">3.4.1 Convenience Functions</A></H3>
 346 <P>Convenience functions are provided to submit an IPP request, send a
 347  print file, cancel a job, get a list of available printers, get a list
 348  of available classes, get the default printer or class, get the default
 349  server name, get the local username, and get a password string.</P>
 350 <H3><A NAME="3_4_2">3.4.2 HTTP Functions</A></H3>
 351 <P>The HTTP functions provide functions to connect to HTTP servers,
 352  issue requests, read data from a server, and write data to a server.</P>
 353 <H3><A NAME="3_4_3">3.4.3 IPP Functions</A></H3>
 354 <P>The IPP function provide functions to manage IPP request data and
 355  attributes, read IPP responses from a server, and write IPP requests to
 356  a server.</P>
 357 <H3><A NAME="3_4_4">3.4.4 Language Functions</A></H3>
 358 <P>The language functions provide a standard interface for retrieving
 359  common textual messages for a particular locale and determining the
 360  correct encoding (e.g. US ASCII, UTF-8, ISO-8859-1, etc.)</P>
 361 <H3><A NAME="3_4_5">3.4.5 PPD Functions</A></H3>
 362 <P>The PostScript Printer Description functions manage PPD files, select
 363  options, check for option conflicts, and emit selected options in the
 364  correct order.</P>
 365 <H2><A NAME="3_5">3.5 CUPS Imaging Library</A></H2>
 366 <P>The CUPS imaging library provides colorspace conversion, color
 367  management, image management, scaling, image file, and raster functions
 368  used by the CUPS raster filters.</P>
 369 <H3><A NAME="3_5_1">3.5.1 Colorspace Conversion Functions</A></H3>
 370 <P>The colorspace conversion functions handle conversion of grayscale
 371  and RGB colors to grayscale, RGB, K, CMY, CMYK, and CMYKcm colorspaces.</P>
 372 <H3><A NAME="3_5_2">3.5.2 Color Management Functions</A></H3>
 373 <P>The color management functions handle gamut mapping and density
 374  correction. These are integrated with the colorspace conversion
 375  functions so that colorspace conversion and color management are
 376  processed in a single step.</P>
 377 <H3><A NAME="3_5_3">3.5.3 Image Management Functions</A></H3>
 378 <P>The image management functions manage a tiled image database that is
 379  swapped to/from disk as needed.</P>
 380 <H3><A NAME="3_5_4">3.5.4 Scaling Functions</A></H3>
 381 <P>The scaling functions provide image scaling services using
 382  nearest-neighbor sampling and bilinear interpolation as appropriate.</P>
 383 <H3><A NAME="3_5_5">3.5.5 Image File Functions</A></H3>
 384 <P>The image file functions handle loading of all image file formats.</P>
 385 <H3><A NAME="3_5_6">3.5.6 Raster Functions</A></H3>
 386 <P>The raster functions manage streams of CUPS raster data (described in
 387  the Interface Design Document) used by non-PostScript printer drivers
 388  and raster filters.</P>
 389 <H2><A NAME="3_6">3.6 Daemons</A></H2>
 390 <P>The daemons provide additional network functions for the scheduler.
 391  Currently only two daemons are provided with CUPS.</P>
 392 <H3><A NAME="3_6_1">3.6.1 Line Printer Daemon</A></H3>
 393 <P>The line printer daemon provides remote LPD client support and is run
 394  by the <CODE>inetd(8)</CODE> daemon as needed.</P>
 395 <H3><A NAME="3_6_2">3.6.2 Polling Daemon</A></H3>
 396 <P>The polling daemon is used to poll a remote server for a list of
 397  available printers and provide it to the scheduler for addition. A
 398  separate polling daemon is run by the scheduler for every remote system
 399  listed for polling in the scheduler configuration file.</P>
 400 <H2><A NAME="3_7">3.7 Filters</A></H2>
 401 <P>The filters implement file conversion services for CUPS. All filters
 402  are called with a common set of arguments:</P>
 403 <UL>
 404 <LI>Printer name - the name of the destination printer (name string).</LI>
 405 <LI>Job Identifier - the job identifier for this job (integer).</LI>
 406 <LI>User Name - the user associated with this job (name string).</LI>
 407 <LI>Title - the title/job-name associated with this job (name string).</LI>
 408 <LI>Copies - the number of copies required (integer).</LI>
 409 <LI>Options - the options associated with this job (space separated
 410  option strings).</LI>
 411 <LI>Filename (optional) - the file to print; if this option is not
 412  specified, the filter must read the input file from the standard input.</LI>
 413 </UL>
 414 <P>Filters are added to the MIME conversion data file and implement all
 415  necessary conversions from one file type to another.</P>
 416 <H3><A NAME="3_7_1">3.7.1 hpgltops</A></H3>
 417 <P>The hpgltops filter converts HP-GL/2 files into PostScript.</P>
 418 <H3><A NAME="3_7_2">3.7.2 imagetops</A></H3>
 419 <P>The imagetops filter converts image files into PostScript.</P>
 420 <H3><A NAME="3_7_3">3.7.3 imagetoraster</A></H3>
 421 <P>The imagetoraster filter converts image files into CUPS raster data.</P>
 422 <H3><A NAME="3_7_4">3.7.4 pdftops</A></H3>
 423 <P>The pdftops filter converts PDF files into PostScript.</P>
 424 <H3><A NAME="3_7_5">3.7.5 pstops</A></H3>
 425 <P>The pstops filter inserts printer-specific commands from PPD files
 426  and performs page filtering as requested by the user.</P>
 427 <H3><A NAME="3_7_6">3.7.6 pstoraster</A></H3>
 428 <P>The pstoraster filter converts PostScript program data into CUPS
 429  raster data.</P>
 430 <H3><A NAME="3_7_7">3.7.7 rastertoepson</A></H3>
 431 <P>The rastertoepson filter handles converting CUPS raster data to ESC/P
 432  and supports both color and black-and-white printers.</P>
 433 <H3><A NAME="3_7_8">3.7.8 rastertohp</A></H3>
 434 <P>The rastertohp filter handles converting CUPS raster data to HP-PCL
 435  and supports both color and black-and-white printers.</P>
 436 <H3><A NAME="3_7_9">3.7.9 texttops</A></H3>
 437 <P>The texttops filter converts text files into PostScript.</P>
 438 <H2><A NAME="3_8">3.8 Scheduler</A></H2>
 439 <P>The scheduler is a fully-functional HTTP/1.1 and IPP/1.1 server that
 440  manages the printers, classes, and jobs in the system. It also handles
 441  a simple broadcast-based directory service so that remote print queues
 442  and classes can be accessed transparently from the local system.</P>
 443 <H3><A NAME="3_8_1">3.8.1 Authorization</A></H3>
 444 <P>The authorization module is responsible for performing access control
 445  and authentication for all HTTP and IPP requests entering the system.</P>
 446 <H3><A NAME="3_8_2">3.8.2 Classes</A></H3>
 447 <P>The classes module is responsible for managing printer classes in the
 448  system. Each class is a collection of local and/or remote printers. The
 449  classes module also reads and writes the classes configuration file.</P>
 450 <H3><A NAME="3_8_3">3.8.3 Client</A></H3>
 451 <P>The client module is responsible for all HTTP client communications.
 452  It handles listening on selected interfaces, accepting connections from
 453  prospective clients, processing incoming HTTP requests, and sending
 454  HTTP responses to those requests. The client module also is responsible
 455  for executing the external CGI programs as needed to support web-based
 456  printer, class, and job status monitoring and administration.</P>
 457 <P>Once authorized, all IPP requests are sent to the IPP module.</P>
 458 <H3><A NAME="3_8_4">3.8.4 Configuration</A></H3>
 459 <P>The configuration module is responsible for reading the CUPS
 460  configuration file and initializing the appropriate data structures and
 461  values. The configuration module also stops CUPS services before
 462  reading the configuration file and restarts them after the
 463  configuration file has been read.</P>
 464 <H3><A NAME="3_8_5">3.8.5 Devices</A></H3>
 465 <P>The devices module is responsible for managing the list of available
 466  devices for the CUPS-Get-Devices operation.</P>
 467 <H3><A NAME="3_8_6">3.8.6 Directory Services</A></H3>
 468 <P>The directory services module sends and recieves printer state
 469  information over a broadcast socket. Remote printers and classes are
 470  automatically added to or removed from the local printer and class
 471  lists as needed.</P>
 472 <P>The directory services module can only recieve printer state
 473  information over a single UDP port, however it can broadcast to
 474  multiple addresses and ports as needed.</P>
 475 <H3><A NAME="3_8_7">3.8.7 IPP</A></H3>
 476 <P>The IPP module handles IPP requests and acts accordingly. URI
 477  validation is also performed here, as a client can post IPP data to any
 478  URI on the server which might sidestep the access control or
 479  authentication of the HTTP server.</P>
 480 <H3><A NAME="3_8_8">3.8.8 Jobs</A></H3>
 481 <P>The jobs module manages print jobs, starts filter and backend
 482  processes for jobs to be printed, and monitors status messages from
 483  those filters and backends.</P>
 484 <H3><A NAME="3_8_9">3.8.9 Logging</A></H3>
 485 <P>The logging module manages the access, error, and page log files that
 486  are generated by the scheduler.</P>
 487 <H3><A NAME="3_8_10">3.8.10 Main</A></H3>
 488 <P>The main module is responsible for timing out and dispatching input
 489  and output for client connections. It also watches for incoming <CODE>
 490 SIGHUP</CODE> and <CODE>SIGCHLD</CODE> signals, reloads the server
 491  configuration files as needed, and handles child process errors and
 492  exits.</P>
 493 <H3><A NAME="3_8_11">3.8.11 MIME</A></H3>
 494 <P>The Multimedia Internet Mail Exchange module manages a MIME type and
 495  conversion database that supports file typing by extension and content
 496  and least-cost file filtering from a source to a destination file type.</P>
 497 <H3><A NAME="3_8_12">3.8.12 PPDs</A></H3>
 498 <P>The PPDs module is responsible for managing the list of available PPD
 499  files for the CUPS-Get-PPDs operation.</P>
 500 <H3><A NAME="3_8_13">3.8.13 Printers</A></H3>
 501 <P>The printers module is responsible for managing printers and PPD
 502  files in the system. The printers module also reads and writes the
 503  printers configuration file.</P>
 504 <H2><A NAME="3_9">3.9 System V Commands</A></H2>
 505 <P>The System V commands provide a robust command-line interface to CUPS
 506  to submit and control printers and jobs.</P>
 507 <H3><A NAME="3_9_1">3.9.1 accept</A></H3>
 508 <P>The accept command tells the scheduler to accept new jobs for
 509  specific printers.</P>
 510 <H3><A NAME="3_9_2">3.9.2 cancel</A></H3>
 511 <P>The cancel command tells the scheduler to cancel one or more jobs
 512  that are queued for printing.</P>
 513 <H3><A NAME="3_9_3">3.9.3 disable</A></H3>
 514 <P>The disable command tells the scheduler to stop printing jobs on the
 515  specified printers.</P>
 516 <H3><A NAME="3_9_4">3.9.4 enable</A></H3>
 517 <P>The enable command tells the scheduler to start printing jobs on the
 518  specified printers.</P>
 519 <H3><A NAME="3_9_5">3.9.5 lp</A></H3>
 520 <P>The lp command submits submits files for printing. Unlike the
 521  standard System V lp command, a single CUPS lp command will generate a
 522  separate job ID for each file that is printed. Also, the Solaris &quot;f&quot;,
 523  &quot;H&quot;, &quot;P&quot;, &quot;S&quot;, and &quot;y&quot; options are silently ignored.</P>
 524 <H3><A NAME="3_9_6">3.9.6 lpadmin</A></H3>
 525 <P>The lpadmin command manages printer queues and classes. The Solaris
 526  &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;,
 527  &quot;s&quot;, &quot;t&quot;, and &quot;u&quot; options are not supported, and new options &quot;P&quot; (PPD
 528  file) and &quot;E&quot; (enable and accept) are provided to configure
 529  CUPS-specific features.</P>
 530 <H3><A NAME="3_9_7">3.9.7 lpinfo</A></H3>
 531 <P>The lpinfo command lists the available PPD files or devices as
 532  selected by the user.</P>
 533 <H3><A NAME="3_9_8">3.9.8 lpmove</A></H3>
 534 <P>The lpmove command moves a print job to a new destination.</P>
 535 <H3><A NAME="3_9_9">3.9.9 lpoptions</A></H3>
 536 <P>The lpoptions command manages user-defined printers and options.</P>
 537 <H3><A NAME="3_9_10">3.9.10 lpstat</A></H3>
 538 <P>The lpstat command lists printers, classes, and jobs as requested by
 539  the user.</P>
 540 <H3><A NAME="3_9_11">3.9.11 reject</A></H3>
 541 <P>The reject command tells the scheduler not to accept new jobs for
 542  specific printers.</P>
 543 <H1 TYPE="A" VALUE="1"><A NAME="4">A Glossary</A></H1>
 544 <H2><A NAME="4_1">A.1 Terms</A></H2>
 545 <DL>
 546 <DT>C</DT>
 547 <DD>A computer language.</DD>
 548 <DT>parallel</DT>
 549 <DD>Sending or receiving data more than 1 bit at a time.</DD>
 550 <DT>pipe</DT>
 551 <DD>A one-way communications channel between two programs.</DD>
 552 <DT>serial</DT>
 553 <DD>Sending or receiving data 1 bit at a time.</DD>
 554 <DT>socket</DT>
 555 <DD>A two-way network communications channel.</DD>
 556 </DL>
 557 <H2><A NAME="4_2">A.2 Acronyms</A></H2>
 558 <DL>
 559 <DT>ASCII</DT>
 560 <DD>American Standard Code for Information Interchange</DD>
 561 <DT>CUPS</DT>
 562 <DD>Common UNIX Printing System</DD>
 563 <DT>ESC/P</DT>
 564 <DD>EPSON Standard Code for Printers</DD>
 565 <DT>FTP</DT>
 566 <DD>File Transfer Protocol</DD>
 567 <DT>HP-GL</DT>
 568 <DD>Hewlett-Packard Graphics Language</DD>
 569 <DT>HP-PCL</DT>
 570 <DD>Hewlett-Packard Page Control Language</DD>
 571 <DT>HP-PJL</DT>
 572 <DD>Hewlett-Packard Printer Job Language</DD>
 573 <DT>IETF</DT>
 574 <DD>Internet Engineering Task Force</DD>
 575 <DT>IPP</DT>
 576 <DD>Internet Printing Protocol</DD>
 577 <DT>ISO</DT>
 578 <DD>International Standards Organization</DD>
 579 <DT>LPD</DT>
 580 <DD>Line Printer Daemon</DD>
 581 <DT>MIME</DT>
 582 <DD>Multimedia Internet Mail Exchange</DD>
 583 <DT>PPD</DT>
 584 <DD>PostScript Printer Description</DD>
 585 <DT>SMB</DT>
 586 <DD>Server Message Block</DD>
 587 <DT>TFTP</DT>
 588 <DD>Trivial File Transfer Protocol</DD>
 589 </DL>
 590 </BODY>
 591 </HTML>