]>
Commit | Line | Data |
---|---|---|
745129be | 1 | <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> |
ef416fc2 | 2 | <html> |
3 | <!-- SECTION: Programming --> | |
4 | <head> | |
5a738aea MS |
5 | <title>Filter and Backend Programming</title> |
6 | <meta name="keywords" content="Programming"> | |
8b450588 | 7 | <meta name="creator" content="Mini-XML v2.6"> |
5a738aea MS |
8 | <style type="text/css"><!-- |
9 | BODY { | |
10 | font-family: lucida grande, geneva, helvetica, arial, sans-serif; | |
11 | } | |
12 | ||
13 | H1, H2, H3, H4, H5, H6, P, TD, TH { | |
14 | font-family: lucida grande, geneva, helvetica, arial, sans-serif; | |
15 | } | |
16 | ||
17 | KBD { | |
18 | font-family: monaco, courier, monospace; | |
19 | font-weight: bold; | |
20 | } | |
21 | ||
22 | PRE { | |
23 | font-family: monaco, courier, monospace; | |
24 | } | |
25 | ||
26 | PRE.command { | |
10d09e33 | 27 | border: dotted thin #7f7f7f; |
5a738aea | 28 | margin-left: 36pt; |
10d09e33 | 29 | padding: 10px; |
5a738aea MS |
30 | } |
31 | ||
f11a948a MS |
32 | P.compact { |
33 | margin: 0; | |
34 | } | |
35 | ||
e4572d57 MS |
36 | P.example { |
37 | font-style: italic; | |
38 | margin-left: 36pt; | |
39 | } | |
40 | ||
5a738aea MS |
41 | PRE.example { |
42 | background: #eeeeee; | |
43 | border: dotted thin #999999; | |
44 | margin-left: 36pt; | |
178cb736 | 45 | padding: 10pt; |
5a738aea MS |
46 | } |
47 | ||
48 | PRE.command EM, PRE.example EM { | |
49 | font-family: lucida grande, geneva, helvetica, arial, sans-serif; | |
50 | } | |
51 | ||
52 | P.command { | |
53 | font-family: monaco, courier, monospace; | |
54 | margin-left: 36pt; | |
55 | } | |
56 | ||
57 | P.formula { | |
58 | font-style: italic; | |
59 | margin-left: 36pt; | |
60 | } | |
61 | ||
62 | BLOCKQUOTE { | |
178cb736 | 63 | background: #eeeeee; |
5a738aea MS |
64 | border: solid thin #999999; |
65 | padding: 10pt; | |
66 | } | |
67 | ||
e4572d57 MS |
68 | A IMG { |
69 | border: none; | |
70 | } | |
71 | ||
72 | A:link:hover IMG { | |
73 | background: #f0f0f0; | |
74 | border-radius: 10px; | |
75 | -moz-border-radius: 10px; | |
76 | } | |
77 | ||
5a738aea | 78 | A:link, A:visited { |
568fa3fa | 79 | font-weight: normal; |
5a738aea | 80 | text-decoration: none; |
5a738aea MS |
81 | } |
82 | ||
83 | A:link:hover, A:visited:hover, A:active { | |
84 | text-decoration: underline; | |
5a738aea MS |
85 | } |
86 | ||
87 | SUB, SUP { | |
88 | font-size: 50%; | |
89 | } | |
90 | ||
e4572d57 MS |
91 | TR.data, TD.data, TR.data TD { |
92 | margin-top: 10pt; | |
93 | padding: 5pt; | |
94 | border-bottom: solid 1pt #999999; | |
95 | } | |
96 | ||
97 | TR.data TH { | |
98 | border-bottom: solid 1pt #999999; | |
99 | padding-top: 10pt; | |
100 | padding-left: 5pt; | |
101 | text-align: left; | |
102 | } | |
103 | ||
5a738aea MS |
104 | DIV.table TABLE { |
105 | border: solid thin #999999; | |
106 | border-collapse: collapse; | |
107 | border-spacing: 0; | |
108 | margin-left: auto; | |
109 | margin-right: auto; | |
110 | } | |
111 | ||
112 | DIV.table CAPTION { | |
113 | caption-side: top; | |
114 | font-size: 120%; | |
115 | font-style: italic; | |
116 | font-weight: bold; | |
117 | margin-left: auto; | |
118 | margin-right: auto; | |
119 | } | |
120 | ||
121 | DIV.table TABLE TD { | |
122 | border: solid thin #cccccc; | |
123 | padding-top: 5pt; | |
124 | } | |
125 | ||
126 | DIV.table TABLE TH { | |
127 | background: #cccccc; | |
128 | border: none; | |
129 | border-bottom: solid thin #999999; | |
130 | } | |
131 | ||
132 | DIV.figure TABLE { | |
133 | margin-left: auto; | |
134 | margin-right: auto; | |
135 | } | |
136 | ||
137 | DIV.figure CAPTION { | |
138 | caption-side: bottom; | |
139 | font-size: 120%; | |
140 | font-style: italic; | |
141 | font-weight: bold; | |
142 | margin-left: auto; | |
143 | margin-right: auto; | |
144 | } | |
145 | ||
146 | TH.label { | |
5a738aea MS |
147 | text-align: right; |
148 | vertical-align: top; | |
149 | } | |
150 | ||
e4572d57 MS |
151 | TH.sublabel { |
152 | text-align: right; | |
153 | font-weight: normal; | |
154 | } | |
155 | ||
5a738aea MS |
156 | HR { |
157 | border: solid thin; | |
158 | } | |
159 | ||
160 | SPAN.info { | |
e4572d57 MS |
161 | background: black; |
162 | border: thin solid black; | |
163 | color: white; | |
5a738aea MS |
164 | font-size: 80%; |
165 | font-style: italic; | |
166 | font-weight: bold; | |
167 | white-space: nowrap; | |
168 | } | |
169 | ||
170 | H2 SPAN.info, H3 SPAN.info, H4 SPAN.info { | |
171 | float: right; | |
172 | font-size: 100%; | |
173 | } | |
174 | ||
178cb736 MS |
175 | H1.title { |
176 | } | |
177 | ||
5a738aea MS |
178 | H2.title, H3.title { |
179 | border-bottom: solid 2pt #000000; | |
180 | } | |
181 | ||
e4572d57 MS |
182 | DIV.indent, TABLE.indent { |
183 | margin-top: 2em; | |
184 | margin-left: auto; | |
185 | margin-right: auto; | |
186 | width: 90%; | |
187 | } | |
188 | ||
189 | TABLE.indent { | |
190 | border-collapse: collapse; | |
191 | } | |
192 | ||
193 | TABLE.indent TD, TABLE.indent TH { | |
194 | padding: 0; | |
195 | } | |
196 | ||
197 | TABLE.list { | |
198 | border-collapse: collapse; | |
199 | margin-left: auto; | |
200 | margin-right: auto; | |
201 | width: 90%; | |
202 | } | |
203 | ||
204 | TABLE.list TH { | |
205 | background: white; | |
206 | border-bottom: solid thin #cccccc; | |
207 | color: #444444; | |
208 | padding-top: 10pt; | |
209 | padding-left: 5pt; | |
210 | text-align: left; | |
211 | vertical-align: bottom; | |
212 | white-space: nowrap; | |
213 | } | |
214 | ||
215 | TABLE.list TH A { | |
216 | color: #4444cc; | |
217 | } | |
218 | ||
219 | TABLE.list TD { | |
220 | border-bottom: solid thin #eeeeee; | |
221 | padding-top: 5pt; | |
222 | padding-left: 5pt; | |
223 | } | |
224 | ||
225 | TABLE.list TR:nth-child(even) { | |
226 | background: #f8f8f8; | |
227 | } | |
228 | ||
229 | TABLE.list TR:nth-child(odd) { | |
230 | background: #f4f4f4; | |
231 | } | |
232 | ||
5a738aea MS |
233 | DT { |
234 | margin-left: 36pt; | |
235 | margin-top: 12pt; | |
236 | } | |
237 | ||
238 | DD { | |
239 | margin-left: 54pt; | |
240 | } | |
241 | ||
242 | DL.category DT { | |
243 | font-weight: bold; | |
244 | } | |
245 | ||
246 | P.summary { | |
247 | margin-left: 36pt; | |
248 | font-family: monaco, courier, monospace; | |
249 | } | |
250 | ||
5a738aea MS |
251 | DIV.summary TABLE { |
252 | border: solid thin #999999; | |
253 | border-collapse: collapse; | |
254 | border-spacing: 0; | |
255 | margin: 10px; | |
256 | } | |
257 | ||
258 | DIV.summary TABLE TD, DIV.summary TABLE TH { | |
259 | border: solid thin #999999; | |
260 | padding: 5px; | |
261 | text-align: left; | |
262 | vertical-align: top; | |
263 | } | |
264 | ||
265 | DIV.summary TABLE THEAD TH { | |
266 | background: #eeeeee; | |
267 | } | |
268 | ||
269 | /* API documentation styles... */ | |
270 | div.body h1 { | |
271 | margin: 0; | |
272 | } | |
273 | div.body h2 { | |
274 | margin-top: 1.5em; | |
275 | } | |
276 | div.body h3, div.body h4, div.body h5 { | |
277 | margin-bottom: 0.5em; | |
278 | margin-top: 1.5em; | |
279 | } | |
280 | .class, .enumeration, .function, .struct, .typedef, .union { | |
281 | border-bottom: solid thin #999999; | |
282 | margin-bottom: 0; | |
283 | margin-top: 2em; | |
284 | } | |
285 | .description { | |
286 | margin-top: 0.5em; | |
287 | } | |
288 | code, p.code, pre, ul.code li { | |
289 | font-family: monaco, courier, monospace; | |
290 | font-size: 90%; | |
291 | } | |
292 | ul.code, ul.contents, ul.subcontents { | |
293 | list-style-type: none; | |
294 | margin: 0; | |
295 | padding-left: 0; | |
296 | } | |
297 | ul.code li { | |
298 | margin: 0; | |
299 | } | |
300 | ul.contents > li { | |
301 | margin-top: 1em; | |
302 | } | |
303 | ul.contents li ul.code, ul.contents li ul.subcontents { | |
304 | padding-left: 2em; | |
305 | } | |
306 | div.body dl { | |
307 | margin-left: 0; | |
308 | margin-top: 0; | |
309 | } | |
310 | div.body dt { | |
311 | font-style: italic; | |
312 | margin-left: 0; | |
313 | margin-top: 0; | |
314 | } | |
315 | div.body dd { | |
316 | margin-bottom: 0.5em; | |
317 | } | |
318 | ||
319 | /* This is just for the HTML files generated with the framedhelp target */ | |
320 | div.contents { | |
321 | background: #e8e8e8; | |
322 | border: solid thin black; | |
323 | padding: 10px; | |
324 | } | |
325 | div.contents h1 { | |
326 | font-size: 110%; | |
327 | } | |
328 | div.contents h2 { | |
329 | font-size: 100%; | |
330 | } | |
331 | div.contents ul.contents { | |
332 | font-size: 80%; | |
333 | } | |
ac884b6a MS |
334 | div.contents ul.subcontents li { |
335 | margin-left: 1em; | |
336 | text-indent: -1em; | |
337 | } | |
5a738aea | 338 | --></style> |
ef416fc2 | 339 | </head> |
340 | <body> | |
5a738aea | 341 | <div class='body'> |
ef416fc2 | 342 | <!-- |
68b10830 | 343 | "$Id$" |
ef416fc2 | 344 | |
5a738aea MS |
345 | Filter and backend programming header for the Common UNIX Printing System |
346 | (CUPS). | |
ef416fc2 | 347 | |
178cb736 | 348 | Copyright 2008-2009 by Apple Inc. |
ef416fc2 | 349 | |
350 | These coded instructions, statements, and computer programs are the | |
bc44d920 | 351 | property of Apple Inc. and are protected by Federal copyright |
352 | law. Distribution and use rights are outlined in the file "LICENSE.txt" | |
353 | which should have been included with this file. If this file is | |
354 | file is missing or damaged, see the license at "http://www.cups.org/". | |
ef416fc2 | 355 | --> |
356 | ||
178cb736 MS |
357 | <h1 class='title'>Filter and Backend Programming</h1> |
358 | ||
5a738aea MS |
359 | <div class='summary'><table summary='General Information'> |
360 | <thead> | |
361 | <tr> | |
ac884b6a | 362 | <th>Headers</th> |
5a738aea | 363 | <th>cups/backend.h<br> |
79e1d494 | 364 | cups/sidechannel.h</th> |
5a738aea MS |
365 | </tr> |
366 | </thead> | |
367 | <tbody> | |
368 | <tr> | |
369 | <th>Library</th> | |
370 | <td>-lcups</td> | |
371 | </tr> | |
372 | <tr> | |
373 | <th>See Also</th> | |
374 | <td>Programming: <a href='api-overview.html' target='_top'>Introduction to CUPS Programming</a><br> | |
375 | Programming: <a href='api-cups.html' target='_top'>CUPS API</a><br> | |
376 | Programming: <a href='api-ppd.html' target='_top'>PPD API</a><br> | |
79e1d494 | 377 | Programming: <a href='api-raster.html' target='_top'>Raster API</a><br> |
b0f6947b MS |
378 | Programming: <a href='postscript-driver.html' target='_top'>Developing PostScript Printer Drivers</a><br> |
379 | Programming: <a href='raster-driver.html' target='_top'>Developing Raster Printer Drivers</a><br> | |
10d09e33 | 380 | Specifications: <a href='spec-design.html' target='_top'>CUPS Design Description</a></td> |
5a738aea MS |
381 | </tr> |
382 | </tbody> | |
383 | </table></div> | |
384 | <h2 class="title">Contents</h2> | |
385 | <ul class="contents"> | |
426c6a59 | 386 | <ul class="subcontents"> |
5a738aea | 387 | <li><a href="#OVERVIEW">Overview</a><ul class="subcontents"> |
ac884b6a | 388 | <li><a href="#SECURITY">Security Considerations</a></li> |
178cb736 | 389 | <li><a href="#PERMISSIONS">File Permissions</a></li> |
ac884b6a MS |
390 | <li><a href="#TEMPFILES">Temporary Files</a></li> |
391 | <li><a href="#COPIES">Copy Generation</a></li> | |
5a738aea MS |
392 | <li><a href="#EXITCODES">Exit Codes</a></li> |
393 | <li><a href="#ENVIRONMENT">Environment Variables</a></li> | |
394 | <li><a href="#MESSAGES">Communicating with the Scheduler</a></li> | |
20fbc903 MS |
395 | <li><a href="#COMMUNICATING_BACKEND">Communicating with the Backend</a></li> |
396 | <li><a href="#COMMUNICATING_FILTER">Communicating with Filters</a></li> | |
ac884b6a | 397 | <li><a href="#SNMP">Doing SNMP Queries with Network Printers</a></li> |
5a738aea MS |
398 | </ul></li> |
399 | <li><a href="#FUNCTIONS">Functions</a><ul class="code"> | |
400 | <li><a href="#cupsBackChannelRead" title="Read data from the backchannel.">cupsBackChannelRead</a></li> | |
401 | <li><a href="#cupsBackChannelWrite" title="Write data to the backchannel.">cupsBackChannelWrite</a></li> | |
ac884b6a | 402 | <li><a href="#cupsBackendDeviceURI" title="Get the device URI for a backend.">cupsBackendDeviceURI</a></li> |
06d4e77b | 403 | <li><a href="#cupsBackendReport" title="Write a device line from a backend.">cupsBackendReport</a></li> |
5a738aea MS |
404 | <li><a href="#cupsSideChannelDoRequest" title="Send a side-channel command to a backend and wait for a response.">cupsSideChannelDoRequest</a></li> |
405 | <li><a href="#cupsSideChannelRead" title="Read a side-channel message.">cupsSideChannelRead</a></li> | |
20fbc903 MS |
406 | <li><a href="#cupsSideChannelSNMPGet" title="Query a SNMP OID's value.">cupsSideChannelSNMPGet</a></li> |
407 | <li><a href="#cupsSideChannelSNMPWalk" title="Query multiple SNMP OID values.">cupsSideChannelSNMPWalk</a></li> | |
5a738aea | 408 | <li><a href="#cupsSideChannelWrite" title="Write a side-channel message.">cupsSideChannelWrite</a></li> |
8b450588 | 409 | </ul></li> |
5a738aea MS |
410 | <li><a href="#TYPES">Data Types</a><ul class="code"> |
411 | <li><a href="#cups_backend_t" title="Backend exit codes">cups_backend_t</a></li> | |
412 | <li><a href="#cups_sc_bidi_t" title="Bidirectional capabilities">cups_sc_bidi_t</a></li> | |
413 | <li><a href="#cups_sc_command_t" title="Request command codes">cups_sc_command_t</a></li> | |
414 | <li><a href="#cups_sc_state_t" title="Printer state bits">cups_sc_state_t</a></li> | |
415 | <li><a href="#cups_sc_status_t" title="Response status codes">cups_sc_status_t</a></li> | |
20fbc903 | 416 | <li><a href="#cups_sc_walk_func_t" title="SNMP walk callback">cups_sc_walk_func_t</a></li> |
5a738aea MS |
417 | </ul></li> |
418 | <li><a href="#ENUMERATIONS">Constants</a><ul class="code"> | |
419 | <li><a href="#cups_backend_e" title="Backend exit codes">cups_backend_e</a></li> | |
79e1d494 | 420 | <li><a href="#cups_sc_bidi_e" title="Bidirectional capability values">cups_sc_bidi_e</a></li> |
5a738aea MS |
421 | <li><a href="#cups_sc_command_e" title="Request command codes">cups_sc_command_e</a></li> |
422 | <li><a href="#cups_sc_state_e" title="Printer state bits">cups_sc_state_e</a></li> | |
423 | <li><a href="#cups_sc_status_e" title="Response status codes">cups_sc_status_e</a></li> | |
424 | </ul></li> | |
5a738aea | 425 | <!-- |
68b10830 | 426 | "$Id$" |
ef416fc2 | 427 | |
5a738aea MS |
428 | Filter and backend programming introduction for the Common UNIX Printing |
429 | System (CUPS). | |
ef416fc2 | 430 | |
178cb736 | 431 | Copyright 2007-2009 by Apple Inc. |
5a738aea | 432 | Copyright 1997-2006 by Easy Software Products, all rights reserved. |
ef416fc2 | 433 | |
5a738aea MS |
434 | These coded instructions, statements, and computer programs are the |
435 | property of Apple Inc. and are protected by Federal copyright | |
436 | law. Distribution and use rights are outlined in the file "LICENSE.txt" | |
437 | which should have been included with this file. If this file is | |
438 | file is missing or damaged, see the license at "http://www.cups.org/". | |
439 | --> | |
f7deaa1a | 440 | |
5a738aea | 441 | <h2 class='title'><a name="OVERVIEW">Overview</a></h2> |
ef416fc2 | 442 | |
79e1d494 MS |
443 | <p>Filters (which include printer drivers and port monitors) and backends |
444 | are used to convert job files to a printable format and send that data to the | |
445 | printer itself. All of these programs use a common interface for processing | |
446 | print jobs and communicating status information to the scheduler. Each is run | |
447 | with a standard set of command-line arguments:<p> | |
ef416fc2 | 448 | |
5a738aea | 449 | <dl class="code"> |
f7deaa1a | 450 | |
5a738aea MS |
451 | <dt>argv[1]</dt> |
452 | <dd>The job ID</dd> | |
ef416fc2 | 453 | |
5a738aea MS |
454 | <dt>argv[2]</dt> |
455 | <dd>The user printing the job</dd> | |
f7deaa1a | 456 | |
5a738aea MS |
457 | <dt>argv[3]</dt> |
458 | <dd>The job name/title</dd> | |
f7deaa1a | 459 | |
5a738aea MS |
460 | <dt>argv[4]</dt> |
461 | <dd>The number of copies to print</dd> | |
f7deaa1a | 462 | |
5a738aea MS |
463 | <dt>argv[5]</dt> |
464 | <dd>The options that were provided when the job was submitted</dd> | |
f7deaa1a | 465 | |
5a738aea | 466 | <dt>argv[6]</dt> |
79e1d494 | 467 | <dd>The file to print (first program only)</dd> |
5a738aea | 468 | </dl> |
f7deaa1a | 469 | |
5a738aea MS |
470 | <p>The scheduler runs one or more of these programs to print any given job. The |
471 | first filter reads from the print file and writes to the standard output, while | |
472 | the remaining filters read from the standard input and write to the standard | |
473 | output. The backend is the last filter in the chain and writes to the | |
474 | device.</p> | |
f7deaa1a | 475 | |
178cb736 MS |
476 | <p>Filters are always run as a non-privileged user, typically "lp", with no |
477 | connection to the user's desktop. Backends are run either as a non-privileged | |
478 | user or as root if the file permissions do not allow user or group execution. | |
479 | The <a href="#PERMISSIONS">file permissions</a> section talks about this in | |
480 | more detail.</p> | |
481 | ||
ac884b6a MS |
482 | <h3><a name="SECURITY">Security Considerations</a></h3> |
483 | ||
484 | <p>It is always important to use security programming practices. Filters and | |
485 | most backends are run as a non-priviledged user, so the major security | |
486 | consideration is resource utilization - filters should not depend on unlimited | |
487 | amounts of CPU, memory, or disk space, and should protect against conditions | |
488 | that could lead to excess usage of any resource like infinite loops and | |
489 | unbounded recursion. In addition, filters must <em>never</em> allow the user to | |
490 | specify an arbitrary file path to a separator page, template, or other file | |
491 | used by the filter since that can lead to an unauthorized disclosure of | |
492 | information. <em>Always</em> treat input as suspect and validate it!</p> | |
493 | ||
4d301e69 | 494 | <p>If you are developing a backend that runs as root, make sure to check for |
ac884b6a MS |
495 | potential buffer overflows, integer under/overflow conditions, and file |
496 | accesses since these can lead to privilege escalations. When writing files, | |
497 | always validate the file path and <em>never</em> allow a user to determine | |
498 | where to store a file.</p> | |
499 | ||
500 | <blockquote><b>Note:</b> | |
501 | ||
502 | <p><em>Never</em> write files to a user's home directory. Aside from the | |
503 | security implications, CUPS is a network print service and as such the network | |
504 | user may not be the same as the local user and/or there may not be a local home | |
505 | directory to write to.</p> | |
506 | ||
507 | <p>In addition, some operating systems provide additional security mechanisms | |
178cb736 | 508 | that further limit file system access, even for backends running as root. On |
ac884b6a MS |
509 | Mac OS X, for example, no backend may write to a user's home directory.</p> |
510 | </blockquote> | |
511 | ||
178cb736 MS |
512 | <h3><a name="PERMISSIONS">File Permissions</a></h3> |
513 | ||
514 | <p>For security reasons, CUPS will only run filters and backends that are owned | |
4d301e69 MS |
515 | by root and do not have world or group write permissions. The recommended |
516 | permissions for filters and backends are 0555 - read and execute but no write. | |
517 | Backends that must run as root should use permissions of 0500 - read and execute | |
518 | by root, no access for other users. Write permissions can be enabled for the | |
519 | root user only.</p> | |
178cb736 MS |
520 | |
521 | <p>To avoid a warning message, the directory containing your filter(s) must also | |
4d301e69 MS |
522 | be owned by root and have world and group write disabled - permissions of 0755 |
523 | or 0555 are strongly encouraged.</p> | |
178cb736 | 524 | |
ac884b6a MS |
525 | <h3><a name="TEMPFILES">Temporary Files</a></h3> |
526 | ||
527 | <p>Temporary files should be created in the directory specified by the | |
528 | "TMPDIR" environment variable. The | |
529 | <a href="#cupsTempFile2"><code>cupsTempFile2</code></a> function can be | |
530 | used to safely create temporary files in this directory.</p> | |
531 | ||
532 | <h3><a name="COPIES">Copy Generation</a></h3> | |
533 | ||
534 | <p>The <code>argv[4]</code> argument specifies the number of copies to produce | |
535 | of the input file. In general, you should only generate copies if the | |
536 | <em>filename</em> argument is supplied. The only exception to this are | |
537 | filters that produce device-independent PostScript output, since the PostScript | |
538 | filter <var>pstops</var> is responsible for generating copies of PostScript | |
539 | files.</p> | |
540 | ||
5a738aea | 541 | <h3><a name="EXITCODES">Exit Codes</a></h3> |
f7deaa1a | 542 | |
5a738aea MS |
543 | <p>Filters must exit with status 0 when they successfully generate print data |
544 | or 1 when they encounter an error. Backends can return any of the | |
545 | <a href="#cups_backend_t"><code>cups_backend_t</code></a> constants.</p> | |
f7deaa1a | 546 | |
5a738aea | 547 | <h3><a name="ENVIRONMENT">Environment Variables</a></h3> |
f7deaa1a | 548 | |
79e1d494 MS |
549 | <p>The following environment variables are defined by the printing system |
550 | when running print filters and backends:</p> | |
f7deaa1a | 551 | |
5a738aea | 552 | <dl class="code"> |
f7deaa1a | 553 | |
acb056cb | 554 | <dt>APPLE_LANGUAGE</dt> |
5a738aea MS |
555 | <dd>The Apple language identifier associated with the job |
556 | (Mac OS X only).</dd> | |
f7deaa1a | 557 | |
5a738aea MS |
558 | <dt>CHARSET</dt> |
559 | <dd>The job character set, typically "utf-8".</dd> | |
f7deaa1a | 560 | |
5a738aea MS |
561 | <dt>CLASS</dt> |
562 | <dd>When a job is submitted to a printer class, contains the name of | |
563 | the destination printer class. Otherwise this environment | |
564 | variable will not be set.</dd> | |
f7deaa1a | 565 | |
5a738aea MS |
566 | <dt>CONTENT_TYPE</dt> |
567 | <dd>The MIME type associated with the file (e.g. | |
568 | application/postscript).</dd> | |
f7deaa1a | 569 | |
5a738aea | 570 | <dt>CUPS_CACHEDIR</dt> |
79e1d494 MS |
571 | <dd>The directory where cache files can be stored. Cache files can be |
572 | used to retain information between jobs or files in a job.</dd> | |
f7deaa1a | 573 | |
5a738aea | 574 | <dt>CUPS_DATADIR</dt> |
79e1d494 | 575 | <dd>The directory where (read-only) CUPS data files can be found.</dd> |
f7deaa1a | 576 | |
758a062f MS |
577 | <dt>CUPS_FILETYPE</dt> |
578 | <dd>The type of file being printed: "job-sheet" for a banner page and | |
579 | "document" for a regular print file.</dd> | |
580 | ||
5a738aea MS |
581 | <dt>CUPS_SERVERROOT</dt> |
582 | <dd>The root directory of the server.</dd> | |
f7deaa1a | 583 | |
5a738aea MS |
584 | <dt>DEVICE_URI</dt> |
585 | <dd>The device-uri associated with the printer.</dd> | |
f7deaa1a | 586 | |
5a738aea MS |
587 | <dt>FINAL_CONTENT_TYPE</dt> |
588 | <dd>The MIME type associated with the printer (e.g. | |
589 | application/vnd.cups-postscript).</dd> | |
f7deaa1a | 590 | |
5a738aea MS |
591 | <dt>LANG</dt> |
592 | <dd>The language locale associated with the job.</dd> | |
f7deaa1a | 593 | |
5a738aea MS |
594 | <dt>PPD</dt> |
595 | <dd>The full pathname of the PostScript Printer Description (PPD) | |
596 | file for this printer.</dd> | |
f7deaa1a | 597 | |
5a738aea | 598 | <dt>PRINTER</dt> |
79e1d494 | 599 | <dd>The queue name of the class or printer.</dd> |
f7deaa1a | 600 | |
5a738aea MS |
601 | <dt>RIP_CACHE</dt> |
602 | <dd>The recommended amount of memory to use for Raster Image | |
603 | Processors (RIPs).</dd> | |
f7deaa1a | 604 | |
79e1d494 MS |
605 | <dt>TMPDIR</dt> |
606 | <dd>The directory where temporary files should be created.</dd> | |
607 | ||
5a738aea | 608 | </dl> |
f7deaa1a | 609 | |
5a738aea | 610 | <h3><a name="MESSAGES">Communicating with the Scheduler</a></h3> |
f7deaa1a | 611 | |
79e1d494 MS |
612 | <p>Filters and backends communicate with the scheduler by writing messages |
613 | to the standard error file. The scheduler reads messages from all filters in | |
614 | a job and processes the message based on its prefix. For example, the following | |
615 | code sets the current printer state message to "Printing page 5":</p> | |
f7deaa1a | 616 | |
5a738aea MS |
617 | <pre class="example"> |
618 | int page = 5; | |
f7deaa1a | 619 | |
5a738aea | 620 | fprintf(stderr, "INFO: Printing page %d\n", page); |
f7deaa1a | 621 | </pre> |
622 | ||
5a738aea MS |
623 | <p>Each message is a single line of text starting with one of the following |
624 | prefix strings:</p> | |
625 | ||
626 | <dl class="code"> | |
627 | ||
628 | <dt>ALERT: message</dt> | |
629 | <dd>Sets the printer-state-message attribute and adds the specified | |
630 | message to the current error log file using the "alert" log level.</dd> | |
631 | ||
632 | <dt>ATTR: attribute=value [attribute=value]</dt> | |
633 | <dd>Sets the named printer or job attribute(s). Typically this is used | |
634 | to set the <code>marker-colors</code>, <code>marker-levels</code>, | |
75bd9771 MS |
635 | <code>marker-message</code>, <code>marker-names</code>, |
636 | <code>marker-types</code>, <code>printer-alert</code>, and | |
637 | <code>printer-alert-description</code> printer attributes. Standard | |
638 | <code>marker-types</code> values are listed in <a href='#TABLE1'>Table | |
639 | 1</a>.</dd> | |
5a738aea MS |
640 | |
641 | <dt>CRIT: message</dt> | |
642 | <dd>Sets the printer-state-message attribute and adds the specified | |
643 | message to the current error log file using the "critical" log | |
644 | level.</dd> | |
645 | ||
646 | <dt>DEBUG: message</dt> | |
647 | <dd>Sets the printer-state-message attribute and adds the specified | |
648 | message to the current error log file using the "debug" log level.</dd> | |
649 | ||
650 | <dt>DEBUG2: message</dt> | |
651 | <dd>Sets the printer-state-message attribute and adds the specified | |
652 | message to the current error log file using the "debug2" log level.</dd> | |
653 | ||
654 | <dt>EMERG: message</dt> | |
655 | <dd>Sets the printer-state-message attribute and adds the specified | |
656 | message to the current error log file using the "emergency" log | |
657 | level.</dd> | |
658 | ||
659 | <dt>ERROR: message</dt> | |
660 | <dd>Sets the printer-state-message attribute and adds the specified | |
79e1d494 MS |
661 | message to the current error log file using the "error" log level. |
662 | Use "ERROR:" messages for non-persistent processing errors.</dd> | |
5a738aea MS |
663 | |
664 | <dt>INFO: message</dt> | |
665 | <dd>Sets the printer-state-message attribute. If the current log level | |
666 | is set to "debug2", also adds the specified message to the current error | |
667 | log file using the "info" log level.</dd> | |
668 | ||
669 | <dt>NOTICE: message</dt> | |
670 | <dd>Sets the printer-state-message attribute and adds the specified | |
671 | message to the current error log file using the "notice" log level.</dd> | |
672 | ||
673 | <dt>PAGE: page-number #-copies</dt> | |
674 | <dt>PAGE: total #-pages</dt> | |
675 | <dd>Adds an entry to the current page log file. The first form adds | |
676 | #-copies to the job-media-sheets-completed attribute. The second | |
677 | form sets the job-media-sheets-completed attribute to #-pages.</dd> | |
678 | ||
20fbc903 MS |
679 | <dt>PPD: keyword=value [keyword=value ...]</dt> |
680 | <dd>Changes or adds keywords to the printer's PPD file. Typically | |
681 | this is used to update installable options or default media settings | |
682 | based on the printer configuration.</dd> | |
683 | ||
5a738aea MS |
684 | <dt>STATE: printer-state-reason [printer-state-reason ...]</dt> |
685 | <dt>STATE: + printer-state-reason [printer-state-reason ...]</dt> | |
686 | <dt>STATE: - printer-state-reason [printer-state-reason ...]</dt> | |
687 | <dd>Sets, adds, or removes printer-state-reason keywords to the | |
79e1d494 MS |
688 | current queue. Typically this is used to indicate persistent media, |
689 | ink, toner, and configuration conditions or errors on a printer. | |
690 | <a href='#TABLE2'>Table 2</a> lists the standard state keywords - | |
acb056cb MS |
691 | use vendor-prefixed ("com.acme.foo") keywords for custom states. |
692 | ||
693 | <blockquote><b>Note:</b> | |
694 | ||
695 | <p>"STATE:" messages often provide visible alerts to the user. For example, on | |
696 | Mac OS X setting a printer-state-reason value with an "-error" or "-warning" | |
697 | suffix will cause the printer's dock item to bounce if the corresponding reason | |
698 | is localized with a cupsIPPReason keyword in the printer's PPD file.</p> | |
699 | ||
700 | </blockquote></dd> | |
5a738aea MS |
701 | |
702 | <dt>WARNING: message</dt> | |
703 | <dd>Sets the printer-state-message attribute and adds the specified | |
704 | message to the current error log file using the "warning" log | |
705 | level.</dd> | |
706 | ||
707 | </dl> | |
708 | ||
709 | <p>Messages without one of these prefixes are treated as if they began with | |
710 | the "DEBUG:" prefix string.</p> | |
711 | ||
79e1d494 MS |
712 | <div class='table'><table width='80%' summary='Table 1: Standard marker-types Values'> |
713 | <caption>Table 1: <a name='TABLE1'>Standard marker-types Values</a></caption> | |
714 | <thead> | |
715 | <tr> | |
716 | <th>marker-type</th> | |
717 | <th>Description</th> | |
718 | </tr> | |
719 | </thead> | |
720 | <tbody> | |
721 | <tr> | |
722 | <td>developer</td> | |
723 | <td>Developer unit</td> | |
724 | </tr> | |
725 | <tr> | |
726 | <td>fuser</td> | |
727 | <td>Fuser unit</td> | |
728 | </tr> | |
729 | <tr> | |
730 | <td>fuserCleaningPad</td> | |
731 | <td>Fuser cleaning pad</td> | |
732 | </tr> | |
733 | <tr> | |
734 | <td>fuserOil</td> | |
735 | <td>Fuser oil</td> | |
736 | </tr> | |
737 | <tr> | |
738 | <td>ink</td> | |
739 | <td>Ink supply</td> | |
740 | </tr> | |
741 | <tr> | |
742 | <td>opc</td> | |
743 | <td>Photo conductor</td> | |
744 | </tr> | |
745 | <tr> | |
746 | <td>solidWax</td> | |
747 | <td>Wax supply</td> | |
748 | </tr> | |
749 | <tr> | |
750 | <td>staples</td> | |
751 | <td>Staple supply</td> | |
752 | </tr> | |
753 | <tr> | |
754 | <td>toner</td> | |
755 | <td>Toner supply</td> | |
756 | </tr> | |
757 | <tr> | |
758 | <td>transferUnit</td> | |
759 | <td>Transfer unit</td> | |
760 | </tr> | |
761 | <tr> | |
762 | <td>wasteInk</td> | |
763 | <td>Waste ink tank</td> | |
764 | </tr> | |
765 | <tr> | |
766 | <td>wasteToner</td> | |
767 | <td>Waste toner tank</td> | |
768 | </tr> | |
769 | <tr> | |
770 | <td>wasteWax</td> | |
771 | <td>Waste wax tank</td> | |
772 | </tr> | |
773 | </tbody> | |
774 | </table></div> | |
775 | ||
776 | <br> | |
777 | ||
778 | <div class='table'><table width='80%' summary='Table 2: Standard State Keywords'> | |
779 | <caption>Table 2: <a name='TABLE2'>Standard State Keywords</a></caption> | |
780 | <thead> | |
781 | <tr> | |
782 | <th>Keyword</th> | |
783 | <th>Description</th> | |
784 | </tr> | |
785 | </thead> | |
786 | <tbody> | |
787 | <tr> | |
788 | <td>connecting-to-device</td> | |
789 | <td>Connecting to printer but not printing yet</td> | |
790 | </tr> | |
791 | <tr> | |
792 | <td>cover-open</td> | |
793 | <td>A cover is open on the printer</td> | |
794 | </tr> | |
795 | <tr> | |
796 | <td>input-tray-missing</td> | |
797 | <td>An input tray is missing from the printer</td> | |
798 | </tr> | |
799 | <tr> | |
800 | <td>marker-supply-empty</td> | |
801 | <td>Out of ink</td> | |
802 | </tr> | |
803 | <tr> | |
804 | <td>marker-supply-low</td> | |
805 | <td>Low on ink</td> | |
806 | </tr> | |
807 | <tr> | |
808 | <td>marker-waste-almost-full</td> | |
809 | <td>Waste tank almost full</td> | |
810 | </tr> | |
811 | <tr> | |
812 | <td>marker-waste-full</td> | |
813 | <td>Waste tank full</td> | |
814 | </tr> | |
815 | <tr> | |
816 | <td>media-empty</td> | |
817 | <td>Out of media</td> | |
818 | </tr> | |
819 | <tr> | |
820 | <td>media-jam</td> | |
821 | <td>Media is jammed in the printer</td> | |
822 | </tr> | |
823 | <tr> | |
824 | <td>media-low</td> | |
825 | <td>Low on media</td> | |
826 | </tr> | |
827 | <tr> | |
828 | <td>paused</td> | |
829 | <td>Stop the printer</td> | |
830 | </tr> | |
831 | <tr> | |
832 | <td>timed-out</td> | |
833 | <td>Unable to connect to printer</td> | |
834 | </tr> | |
835 | <tr> | |
836 | <td>toner-empty</td> | |
837 | <td>Out of toner</td> | |
838 | </tr> | |
839 | <tr> | |
840 | <td>toner-low</td> | |
841 | <td>Low on toner</td> | |
842 | </tr> | |
843 | </tbody> | |
844 | </table></div> | |
845 | ||
20fbc903 | 846 | <h3><a name="COMMUNICATING_BACKEND">Communicating with the Backend</a></h3> |
5a738aea MS |
847 | |
848 | <p>Filters can communicate with the backend via the | |
849 | <a href="#cupsBackChannelRead"><code>cupsBackChannelRead</code></a> and | |
850 | <a href="#cupsSideChannelDoRequest"><code>cupsSideChannelDoRequest</code></a> | |
851 | functions. The | |
852 | <a href="#cupsBackChannelRead"><code>cupsBackChannelRead</code></a> function | |
853 | reads data that has been sent back from the device and is typically used to | |
854 | obtain status and configuration information. For example, the following code | |
855 | polls the backend for back-channel data:</p> | |
856 | ||
857 | <pre class="example"> | |
858 | #include <cups/cups.h> | |
859 | ||
860 | char buffer[8192]; | |
861 | ssize_t bytes; | |
862 | ||
863 | /* Use a timeout of 0.0 seconds to poll for back-channel data */ | |
864 | bytes = cupsBackChannelRead(buffer, sizeof(buffer), 0.0); | |
865 | </pre> | |
f7deaa1a | 866 | |
79e1d494 MS |
867 | <p>Filters can also use <code>select()</code> or <code>poll()</code> on the |
868 | back-channel file descriptor (3 or <code>CUPS_BC_FD</code>) to read data only | |
869 | when it is available.</p> | |
870 | ||
871 | <p>The | |
5a738aea MS |
872 | <a href="#cupsSideChannelDoRequest"><code>cupsSideChannelDoRequest</code></a> |
873 | function allows you to get out-of-band status information and do synchronization | |
874 | with the device. For example, the following code gets the current IEEE-1284 | |
875 | device ID string from the backend:</p> | |
876 | ||
877 | <pre class="example"> | |
f7deaa1a | 878 | #include <cups/sidechannel.h> |
879 | ||
880 | char data[2049]; | |
881 | int datalen; | |
5a738aea | 882 | <a href="#cups_sc_status_t">cups_sc_status_t</a> status; |
f7deaa1a | 883 | |
79e1d494 MS |
884 | /* Tell cupsSideChannelDoRequest() how big our buffer is, less 1 byte for |
885 | nul-termination... */ | |
f7deaa1a | 886 | datalen = sizeof(data) - 1; |
887 | ||
888 | /* Get the IEEE-1284 device ID, waiting for up to 1 second */ | |
5a738aea | 889 | status = <a href="#cupsSideChannelDoRequest">cupsSideChannelDoRequest</a>(CUPS_SC_CMD_GET_DEVICE_ID, data, &datalen, 1.0); |
f7deaa1a | 890 | |
891 | /* Use the returned value if OK was returned and the length is non-zero */ | |
892 | if (status == CUPS_SC_STATUS_OK && datalen > 0) | |
893 | data[datalen] = '\0'; | |
894 | else | |
895 | data[0] = '\0'; | |
896 | </pre> | |
897 | ||
20fbc903 MS |
898 | <h3><a name="COMMUNICATING_FILTER">Communicating with Filters</a></h3> |
899 | ||
5a738aea MS |
900 | <p>Backends communicate with filters using the reciprocal functions |
901 | <a href="#cupsBackChannelWrite"><code>cupsBackChannelWrite</code></a>, | |
902 | <a href="#cupsSideChannelRead"><code>cupsSideChannelRead</code></a>, and | |
903 | <a href="#cupsSideChannelWrite"><code>cupsSideChannelWrite</code></a>. We | |
904 | recommend writing back-channel data using a timeout of 1.0 seconds:</p> | |
f7deaa1a | 905 | |
5a738aea MS |
906 | <pre class="example"> |
907 | #include <cups/cups.h> | |
f7deaa1a | 908 | |
5a738aea MS |
909 | char buffer[8192]; |
910 | ssize_t bytes; | |
f7deaa1a | 911 | |
79e1d494 MS |
912 | /* Obtain data from printer/device */ |
913 | ... | |
914 | ||
5a738aea MS |
915 | /* Use a timeout of 1.0 seconds to give filters a chance to read */ |
916 | cupsBackChannelWrite(buffer, bytes, 1.0); | |
f7deaa1a | 917 | </pre> |
918 | ||
5a738aea MS |
919 | <p>The <a href="#cupsSideChannelRead"><code>cupsSideChannelRead</code></a> |
920 | function reads a side-channel command from a filter, driver, or port monitor. | |
921 | Backends can either poll for commands using a <code>timeout</code> of 0.0, wait | |
922 | indefinitely for commands using a <code>timeout</code> of -1.0 (probably in a | |
923 | separate thread for that purpose), or use <code>select</code> or | |
924 | <code>poll</code> on the <code>CUPS_SC_FD</code> file descriptor (4) to handle | |
20fbc903 | 925 | input and output on several file descriptors at the same time.</p> |
5a738aea MS |
926 | |
927 | <p>Once a command is processed, the backend uses the | |
928 | <a href="#cupsSideChannelWrite"><code>cupsSideChannelWrite</code></a> function | |
929 | to send its response. For example, the following code shows how to poll for a | |
930 | side-channel command and respond to it:</p> | |
931 | ||
932 | <pre class="example"> | |
f7deaa1a | 933 | #include <cups/sidechannel.h> |
934 | ||
5a738aea MS |
935 | <a href="#cups_sc_command_t">cups_sc_command_t</a> command; |
936 | <a href="#cups_sc_status_t">cups_sc_status_t</a> status; | |
20fbc903 MS |
937 | char data[2048]; |
938 | int datalen = sizeof(data); | |
f7deaa1a | 939 | |
940 | /* Poll for a command... */ | |
20fbc903 | 941 | if (!<a href="#cupsSideChannelRead">cupsSideChannelRead</a>(&command, &status, data, &datalen, 0.0)) |
f7deaa1a | 942 | { |
f7deaa1a | 943 | switch (command) |
944 | { | |
20fbc903 | 945 | /* handle supported commands, fill data/datalen/status with values as needed */ |
f7deaa1a | 946 | |
947 | default : | |
948 | status = CUPS_SC_STATUS_NOT_IMPLEMENTED; | |
949 | datalen = 0; | |
950 | break; | |
951 | } | |
952 | ||
953 | /* Send a response... */ | |
5a738aea | 954 | <a href="#cupsSideChannelWrite">cupsSideChannelWrite</a>(command, status, data, datalen, 1.0); |
f7deaa1a | 955 | } |
956 | </pre> | |
ac884b6a MS |
957 | |
958 | <h3><a name="SNMP">Doing SNMP Queries with Network Printers</a></h3> | |
959 | ||
960 | <p>The Simple Network Management Protocol (SNMP) allows you to get the current | |
961 | status, page counter, and supply levels from most network printers. Every | |
962 | piece of information is associated with an Object Identifier (OID), and | |
963 | every printer has a <em>community</em> name associated with it. OIDs can be | |
964 | queried directly or by "walking" over a range of OIDs with a common prefix.</p> | |
965 | ||
20fbc903 MS |
966 | <p>The two CUPS SNMP functions provide a simple API for querying network |
967 | printers through the side-channel interface. Each accepts a string containing | |
968 | an OID like ".1.3.6.1.2.1.43.10.2.1.4.1.1" (the standard page counter OID) | |
969 | along with a timeout for the query.</p> | |
ac884b6a | 970 | |
20fbc903 MS |
971 | <p>The <a href="#cupsSideChannelSNMPGet"><code>cupsSideChannelSNMPGet</code></a> |
972 | function queries a single OID and returns the value as a string in a buffer | |
973 | you supply:</p> | |
ac884b6a MS |
974 | |
975 | <pre class="example"> | |
20fbc903 | 976 | #include <cups/sidechannel.h> |
ac884b6a | 977 | |
20fbc903 MS |
978 | char data[512]; |
979 | int datalen = sizeof(data); | |
ac884b6a | 980 | |
20fbc903 MS |
981 | if (<a href="#cupsSideChannelSNMPGet">cupsSideChannelSNMPGet</a>(".1.3.6.1.2.1.43.10.2.1.4.1.1", data, &datalen, 5.0) |
982 | == CUPS_SC_STATUS_OK) | |
ac884b6a MS |
983 | { |
984 | /* Do something with the value */ | |
20fbc903 | 985 | printf("Page counter is: %s\n", data); |
ac884b6a MS |
986 | } |
987 | </pre> | |
988 | ||
20fbc903 MS |
989 | <p>The |
990 | <a href="#cupsSideChannelSNMPWalk"><code>cupsSideChannelSNMPWalk</code></a> | |
991 | function allows you to query a whole group of OIDs, calling a function of your | |
992 | choice for each OID that is found:</p> | |
ac884b6a MS |
993 | |
994 | <pre class="example"> | |
20fbc903 | 995 | #include <cups/sidechannel.h> |
ac884b6a MS |
996 | |
997 | void | |
20fbc903 | 998 | my_callback(const char *oid, const char *data, int datalen, void *context) |
ac884b6a MS |
999 | { |
1000 | /* Do something with the value */ | |
20fbc903 | 1001 | printf("%s=%s\n", oid, data); |
ac884b6a MS |
1002 | } |
1003 | ||
20fbc903 MS |
1004 | ... |
1005 | ||
ac884b6a MS |
1006 | void *my_data; |
1007 | ||
20fbc903 | 1008 | <a href="#cupsSideChannelSNMPWalk">cupsSNMPSideChannelWalk</a>(".1.3.6.1.2.1.43", 5.0, my_callback, my_data); |
ac884b6a | 1009 | </pre> |
20fbc903 | 1010 | <h2 class="title"><a name="FUNCTIONS">Functions</a></h2> |
426c6a59 | 1011 | <h3 class="function"><span class="info"> CUPS 1.2/Mac OS X 10.5 </span><a name="cupsBackChannelRead">cupsBackChannelRead</a></h3> |
5a738aea MS |
1012 | <p class="description">Read data from the backchannel.</p> |
1013 | <p class="code"> | |
1014 | ssize_t cupsBackChannelRead (<br> | |
1015 | char *buffer,<br> | |
1016 | size_t bytes,<br> | |
1017 | double timeout<br> | |
1018 | );</p> | |
1019 | <h4 class="parameters">Parameters</h4> | |
1020 | <dl> | |
1021 | <dt>buffer</dt> | |
79e1d494 | 1022 | <dd class="description">Buffer to read into</dd> |
5a738aea MS |
1023 | <dt>bytes</dt> |
1024 | <dd class="description">Bytes to read</dd> | |
1025 | <dt>timeout</dt> | |
79e1d494 | 1026 | <dd class="description">Timeout in seconds, typically 0.0 to poll</dd> |
5a738aea MS |
1027 | </dl> |
1028 | <h4 class="returnvalue">Return Value</h4> | |
1029 | <p class="description">Bytes read or -1 on error</p> | |
1030 | <h4 class="discussion">Discussion</h4> | |
79e1d494 MS |
1031 | <p class="discussion">Reads up to "bytes" bytes from the backchannel/backend. The "timeout" |
1032 | parameter controls how many seconds to wait for the data - use 0.0 to | |
1033 | return immediately if there is no data, -1.0 to wait for data indefinitely. | |
ef416fc2 | 1034 | |
5a738aea | 1035 | </p> |
426c6a59 | 1036 | <h3 class="function"><span class="info"> CUPS 1.2/Mac OS X 10.5 </span><a name="cupsBackChannelWrite">cupsBackChannelWrite</a></h3> |
5a738aea MS |
1037 | <p class="description">Write data to the backchannel.</p> |
1038 | <p class="code"> | |
1039 | ssize_t cupsBackChannelWrite (<br> | |
1040 | const char *buffer,<br> | |
1041 | size_t bytes,<br> | |
1042 | double timeout<br> | |
1043 | );</p> | |
1044 | <h4 class="parameters">Parameters</h4> | |
1045 | <dl> | |
1046 | <dt>buffer</dt> | |
1047 | <dd class="description">Buffer to write</dd> | |
1048 | <dt>bytes</dt> | |
1049 | <dd class="description">Bytes to write</dd> | |
1050 | <dt>timeout</dt> | |
79e1d494 | 1051 | <dd class="description">Timeout in seconds, typically 1.0</dd> |
5a738aea MS |
1052 | </dl> |
1053 | <h4 class="returnvalue">Return Value</h4> | |
1054 | <p class="description">Bytes written or -1 on error</p> | |
1055 | <h4 class="discussion">Discussion</h4> | |
79e1d494 | 1056 | <p class="discussion">Writes "bytes" bytes to the backchannel/filter. The "timeout" parameter |
ef416fc2 | 1057 | controls how many seconds to wait for the data to be written - use |
1058 | 0.0 to return immediately if the data cannot be written, -1.0 to wait | |
1059 | indefinitely. | |
1060 | ||
ac884b6a | 1061 | </p> |
426c6a59 | 1062 | <h3 class="function"><span class="info"> CUPS 1.2/Mac OS X 10.5 </span><a name="cupsBackendDeviceURI">cupsBackendDeviceURI</a></h3> |
ac884b6a MS |
1063 | <p class="description">Get the device URI for a backend.</p> |
1064 | <p class="code"> | |
1065 | const char *cupsBackendDeviceURI (<br> | |
1066 | char **argv<br> | |
1067 | );</p> | |
1068 | <h4 class="parameters">Parameters</h4> | |
1069 | <dl> | |
1070 | <dt>argv</dt> | |
1071 | <dd class="description">Command-line arguments</dd> | |
1072 | </dl> | |
1073 | <h4 class="returnvalue">Return Value</h4> | |
1074 | <p class="description">Device URI or <code>NULL</code></p> | |
1075 | <h4 class="discussion">Discussion</h4> | |
1076 | <p class="discussion">The "argv" argument is the argv argument passed to main(). This | |
1077 | function returns the device URI passed in the DEVICE_URI environment | |
1078 | variable or the device URI passed in argv[0], whichever is found | |
426c6a59 MS |
1079 | first. |
1080 | ||
1081 | </p> | |
178cb736 | 1082 | <h3 class="function"><span class="info"> CUPS 1.4/Mac OS X 10.6 </span><a name="cupsBackendReport">cupsBackendReport</a></h3> |
06d4e77b MS |
1083 | <p class="description">Write a device line from a backend.</p> |
1084 | <p class="code"> | |
1085 | void cupsBackendReport (<br> | |
1086 | const char *device_scheme,<br> | |
1087 | const char *device_uri,<br> | |
1088 | const char *device_make_and_model,<br> | |
1089 | const char *device_info,<br> | |
1090 | const char *device_id,<br> | |
1091 | const char *device_location<br> | |
1092 | );</p> | |
1093 | <h4 class="parameters">Parameters</h4> | |
1094 | <dl> | |
1095 | <dt>device_scheme</dt> | |
1096 | <dd class="description">device-scheme string</dd> | |
1097 | <dt>device_uri</dt> | |
1098 | <dd class="description">device-uri string</dd> | |
1099 | <dt>device_make_and_model</dt> | |
1100 | <dd class="description">device-make-and-model string or <code>NULL</code></dd> | |
1101 | <dt>device_info</dt> | |
1102 | <dd class="description">device-info string or <code>NULL</code></dd> | |
1103 | <dt>device_id</dt> | |
1104 | <dd class="description">device-id string or <code>NULL</code></dd> | |
1105 | <dt>device_location</dt> | |
1106 | <dd class="description">device-location string or <code>NULL</code></dd> | |
1107 | </dl> | |
1108 | <h4 class="discussion">Discussion</h4> | |
1109 | <p class="discussion">This function writes a single device line to stdout for a backend. | |
1110 | It handles quoting of special characters in the device-make-and-model, | |
426c6a59 MS |
1111 | device-info, device-id, and device-location strings. |
1112 | ||
1113 | </p> | |
1114 | <h3 class="function"><span class="info"> CUPS 1.3/Mac OS X 10.5 </span><a name="cupsSideChannelDoRequest">cupsSideChannelDoRequest</a></h3> | |
5a738aea MS |
1115 | <p class="description">Send a side-channel command to a backend and wait for a response.</p> |
1116 | <p class="code"> | |
1117 | <a href="#cups_sc_status_t">cups_sc_status_t</a> cupsSideChannelDoRequest (<br> | |
1118 | <a href="#cups_sc_command_t">cups_sc_command_t</a> command,<br> | |
1119 | char *data,<br> | |
1120 | int *datalen,<br> | |
1121 | double timeout<br> | |
1122 | );</p> | |
1123 | <h4 class="parameters">Parameters</h4> | |
1124 | <dl> | |
1125 | <dt>command</dt> | |
1126 | <dd class="description">Command to send</dd> | |
1127 | <dt>data</dt> | |
1128 | <dd class="description">Response data buffer pointer</dd> | |
1129 | <dt>datalen</dt> | |
1130 | <dd class="description">Size of data buffer on entry, number of bytes in buffer on return</dd> | |
1131 | <dt>timeout</dt> | |
1132 | <dd class="description">Timeout in seconds</dd> | |
1133 | </dl> | |
1134 | <h4 class="returnvalue">Return Value</h4> | |
1135 | <p class="description">Status of command</p> | |
1136 | <h4 class="discussion">Discussion</h4> | |
1137 | <p class="discussion">This function is normally only called by filters, drivers, or port | |
f7deaa1a | 1138 | monitors in order to communicate with the backend used by the current |
1139 | printer. Programs must be prepared to handle timeout or "not | |
1140 | implemented" status codes, which indicate that the backend or device | |
5a738aea MS |
1141 | do not support the specified side-channel command.<br> |
1142 | <br> | |
1143 | The "datalen" parameter must be initialized to the size of the buffer | |
f7deaa1a | 1144 | pointed to by the "data" parameter. cupsSideChannelDoRequest() will |
1145 | update the value to contain the number of data bytes in the buffer. | |
1146 | ||
5a738aea | 1147 | </p> |
426c6a59 | 1148 | <h3 class="function"><span class="info"> CUPS 1.3/Mac OS X 10.5 </span><a name="cupsSideChannelRead">cupsSideChannelRead</a></h3> |
5a738aea MS |
1149 | <p class="description">Read a side-channel message.</p> |
1150 | <p class="code"> | |
1151 | int cupsSideChannelRead (<br> | |
1152 | <a href="#cups_sc_command_t">cups_sc_command_t</a> *command,<br> | |
1153 | <a href="#cups_sc_status_t">cups_sc_status_t</a> *status,<br> | |
1154 | char *data,<br> | |
1155 | int *datalen,<br> | |
1156 | double timeout<br> | |
1157 | );</p> | |
1158 | <h4 class="parameters">Parameters</h4> | |
1159 | <dl> | |
1160 | <dt>command</dt> | |
1161 | <dd class="description">Command code</dd> | |
1162 | <dt>status</dt> | |
1163 | <dd class="description">Status code</dd> | |
1164 | <dt>data</dt> | |
1165 | <dd class="description">Data buffer pointer</dd> | |
1166 | <dt>datalen</dt> | |
1167 | <dd class="description">Size of data buffer on entry, number of bytes in buffer on return</dd> | |
1168 | <dt>timeout</dt> | |
1169 | <dd class="description">Timeout in seconds</dd> | |
1170 | </dl> | |
1171 | <h4 class="returnvalue">Return Value</h4> | |
1172 | <p class="description">0 on success, -1 on error</p> | |
1173 | <h4 class="discussion">Discussion</h4> | |
1174 | <p class="discussion">This function is normally only called by backend programs to read | |
f7deaa1a | 1175 | commands from a filter, driver, or port monitor program. The |
1176 | caller must be prepared to handle incomplete or invalid messages | |
5a738aea MS |
1177 | and return the corresponding status codes.<br> |
1178 | <br> | |
1179 | The "datalen" parameter must be initialized to the size of the buffer | |
f7deaa1a | 1180 | pointed to by the "data" parameter. cupsSideChannelDoRequest() will |
1181 | update the value to contain the number of data bytes in the buffer. | |
1182 | ||
20fbc903 | 1183 | </p> |
178cb736 | 1184 | <h3 class="function"><span class="info"> CUPS 1.4/Mac OS X 10.6 </span><a name="cupsSideChannelSNMPGet">cupsSideChannelSNMPGet</a></h3> |
20fbc903 MS |
1185 | <p class="description">Query a SNMP OID's value.</p> |
1186 | <p class="code"> | |
1187 | <a href="#cups_sc_status_t">cups_sc_status_t</a> cupsSideChannelSNMPGet (<br> | |
1188 | const char *oid,<br> | |
1189 | char *data,<br> | |
1190 | int *datalen,<br> | |
1191 | double timeout<br> | |
1192 | );</p> | |
1193 | <h4 class="parameters">Parameters</h4> | |
1194 | <dl> | |
1195 | <dt>oid</dt> | |
1196 | <dd class="description">OID to query</dd> | |
1197 | <dt>data</dt> | |
1198 | <dd class="description">Buffer for OID value</dd> | |
1199 | <dt>datalen</dt> | |
1200 | <dd class="description">Size of OID buffer on entry, size of value on return</dd> | |
1201 | <dt>timeout</dt> | |
1202 | <dd class="description">Timeout in seconds</dd> | |
1203 | </dl> | |
1204 | <h4 class="returnvalue">Return Value</h4> | |
1205 | <p class="description">Query status</p> | |
1206 | <h4 class="discussion">Discussion</h4> | |
1207 | <p class="discussion">This function asks the backend to do a SNMP OID query on behalf of the | |
1208 | filter, port monitor, or backend using the default community name.<br> | |
1209 | <br> | |
1210 | "oid" contains a numeric OID consisting of integers separated by periods, | |
1211 | for example ".1.3.6.1.2.1.43". Symbolic names from SNMP MIBs are not | |
1212 | supported and must be converted to their numeric forms.<br> | |
1213 | <br> | |
1214 | On input, "data" and "datalen" provide the location and size of the | |
1215 | buffer to hold the OID value as a string. HEX-String (binary) values are | |
1216 | converted to hexadecimal strings representing the binary data, while | |
1217 | NULL-Value and unknown OID types are returned as the empty string. | |
1218 | The returned "datalen" does not include the trailing nul. | |
1219 | ||
1220 | <code>CUPS_SC_STATUS_NOT_IMPLEMENTED</code> is returned by backends that do not | |
1221 | support SNMP queries. <code>CUPS_SC_STATUS_NO_RESPONSE</code> is returned when | |
1222 | the printer does not respond to the SNMP query. | |
1223 | ||
1224 | </p> | |
178cb736 | 1225 | <h3 class="function"><span class="info"> CUPS 1.4/Mac OS X 10.6 </span><a name="cupsSideChannelSNMPWalk">cupsSideChannelSNMPWalk</a></h3> |
20fbc903 MS |
1226 | <p class="description">Query multiple SNMP OID values.</p> |
1227 | <p class="code"> | |
1228 | <a href="#cups_sc_status_t">cups_sc_status_t</a> cupsSideChannelSNMPWalk (<br> | |
1229 | const char *oid,<br> | |
1230 | double timeout,<br> | |
1231 | <a href="#cups_sc_walk_func_t">cups_sc_walk_func_t</a> cb,<br> | |
1232 | void *context<br> | |
1233 | );</p> | |
1234 | <h4 class="parameters">Parameters</h4> | |
1235 | <dl> | |
1236 | <dt>oid</dt> | |
1237 | <dd class="description">First numeric OID to query</dd> | |
1238 | <dt>timeout</dt> | |
1239 | <dd class="description">Timeout for each query in seconds</dd> | |
1240 | <dt>cb</dt> | |
1241 | <dd class="description">Function to call with each value</dd> | |
1242 | <dt>context</dt> | |
1243 | <dd class="description">Application-defined pointer to send to callback</dd> | |
1244 | </dl> | |
1245 | <h4 class="returnvalue">Return Value</h4> | |
1246 | <p class="description">Status of first query of <code>CUPS_SC_STATUS_OK</code> on success</p> | |
1247 | <h4 class="discussion">Discussion</h4> | |
1248 | <p class="discussion">This function asks the backend to do multiple SNMP OID queries on behalf | |
1249 | of the filter, port monitor, or backend using the default community name. | |
1250 | All OIDs under the "parent" OID are queried and the results are sent to | |
1251 | the callback function you provide.<br> | |
1252 | <br> | |
1253 | "oid" contains a numeric OID consisting of integers separated by periods, | |
1254 | for example ".1.3.6.1.2.1.43". Symbolic names from SNMP MIBs are not | |
1255 | supported and must be converted to their numeric forms.<br> | |
1256 | <br> | |
1257 | "timeout" specifies the timeout for each OID query. The total amount of | |
1258 | time will depend on the number of OID values found and the time required | |
1259 | for each query.<br> | |
1260 | <br> | |
1261 | "cb" provides a function to call for every value that is found. "context" | |
1262 | is an application-defined pointer that is sent to the callback function | |
1263 | along with the OID and current data. The data passed to the callback is the | |
1264 | same as returned by <a href="#cupsSideChannelSNMPGet"><code>cupsSideChannelSNMPGet</code></a>. | |
1265 | ||
1266 | <code>CUPS_SC_STATUS_NOT_IMPLEMENTED</code> is returned by backends that do not | |
1267 | support SNMP queries. <code>CUPS_SC_STATUS_NO_RESPONSE</code> is returned when | |
1268 | the printer does not respond to the first SNMP query. | |
1269 | ||
5a738aea | 1270 | </p> |
426c6a59 | 1271 | <h3 class="function"><span class="info"> CUPS 1.3/Mac OS X 10.5 </span><a name="cupsSideChannelWrite">cupsSideChannelWrite</a></h3> |
5a738aea MS |
1272 | <p class="description">Write a side-channel message.</p> |
1273 | <p class="code"> | |
1274 | int cupsSideChannelWrite (<br> | |
1275 | <a href="#cups_sc_command_t">cups_sc_command_t</a> command,<br> | |
1276 | <a href="#cups_sc_status_t">cups_sc_status_t</a> status,<br> | |
1277 | const char *data,<br> | |
1278 | int datalen,<br> | |
1279 | double timeout<br> | |
1280 | );</p> | |
1281 | <h4 class="parameters">Parameters</h4> | |
1282 | <dl> | |
1283 | <dt>command</dt> | |
1284 | <dd class="description">Command code</dd> | |
1285 | <dt>status</dt> | |
1286 | <dd class="description">Status code</dd> | |
1287 | <dt>data</dt> | |
1288 | <dd class="description">Data buffer pointer</dd> | |
1289 | <dt>datalen</dt> | |
1290 | <dd class="description">Number of bytes of data</dd> | |
1291 | <dt>timeout</dt> | |
1292 | <dd class="description">Timeout in seconds</dd> | |
1293 | </dl> | |
1294 | <h4 class="returnvalue">Return Value</h4> | |
1295 | <p class="description">0 on success, -1 on error</p> | |
1296 | <h4 class="discussion">Discussion</h4> | |
1297 | <p class="discussion">This function is normally only called by backend programs to send | |
f7deaa1a | 1298 | responses to a filter, driver, or port monitor program. |
1299 | ||
5a738aea MS |
1300 | </p> |
1301 | <h2 class="title"><a name="TYPES">Data Types</a></h2> | |
1302 | <h3 class="typedef"><a name="cups_backend_t">cups_backend_t</a></h3> | |
1303 | <p class="description">Backend exit codes</p> | |
1304 | <p class="code"> | |
1305 | typedef enum <a href="#cups_backend_e">cups_backend_e</a> cups_backend_t; | |
1306 | </p> | |
1307 | <h3 class="typedef"><a name="cups_sc_bidi_t">cups_sc_bidi_t</a></h3> | |
1308 | <p class="description">Bidirectional capabilities</p> | |
1309 | <p class="code"> | |
1310 | typedef enum <a href="#cups_sc_bidi_e">cups_sc_bidi_e</a> cups_sc_bidi_t; | |
1311 | </p> | |
1312 | <h3 class="typedef"><a name="cups_sc_command_t">cups_sc_command_t</a></h3> | |
1313 | <p class="description">Request command codes</p> | |
1314 | <p class="code"> | |
1315 | typedef enum <a href="#cups_sc_command_e">cups_sc_command_e</a> cups_sc_command_t; | |
1316 | </p> | |
1317 | <h3 class="typedef"><a name="cups_sc_state_t">cups_sc_state_t</a></h3> | |
1318 | <p class="description">Printer state bits</p> | |
1319 | <p class="code"> | |
1320 | typedef enum <a href="#cups_sc_state_e">cups_sc_state_e</a> cups_sc_state_t; | |
1321 | </p> | |
1322 | <h3 class="typedef"><a name="cups_sc_status_t">cups_sc_status_t</a></h3> | |
1323 | <p class="description">Response status codes</p> | |
1324 | <p class="code"> | |
1325 | typedef enum <a href="#cups_sc_status_e">cups_sc_status_e</a> cups_sc_status_t; | |
1326 | </p> | |
20fbc903 MS |
1327 | <h3 class="typedef"><a name="cups_sc_walk_func_t">cups_sc_walk_func_t</a></h3> |
1328 | <p class="description">SNMP walk callback</p> | |
1329 | <p class="code"> | |
1330 | typedef void (*cups_sc_walk_func_t)(const char *oid, const char *data, int datalen, void *context); | |
1331 | </p> | |
5a738aea MS |
1332 | <h2 class="title"><a name="ENUMERATIONS">Constants</a></h2> |
1333 | <h3 class="enumeration"><a name="cups_backend_e">cups_backend_e</a></h3> | |
1334 | <p class="description">Backend exit codes</p> | |
1335 | <h4 class="constants">Constants</h4> | |
1336 | <dl> | |
1337 | <dt>CUPS_BACKEND_AUTH_REQUIRED </dt> | |
1338 | <dd class="description">Job failed, authentication required</dd> | |
1339 | <dt>CUPS_BACKEND_CANCEL </dt> | |
1340 | <dd class="description">Job failed, cancel job</dd> | |
1341 | <dt>CUPS_BACKEND_FAILED </dt> | |
1342 | <dd class="description">Job failed, use error-policy</dd> | |
1343 | <dt>CUPS_BACKEND_HOLD </dt> | |
1344 | <dd class="description">Job failed, hold job</dd> | |
1345 | <dt>CUPS_BACKEND_OK </dt> | |
1346 | <dd class="description">Job completed successfully</dd> | |
1347 | <dt>CUPS_BACKEND_STOP </dt> | |
1348 | <dd class="description">Job failed, stop queue</dd> | |
1349 | </dl> | |
1350 | <h3 class="enumeration"><a name="cups_sc_bidi_e">cups_sc_bidi_e</a></h3> | |
79e1d494 | 1351 | <p class="description">Bidirectional capability values</p> |
5a738aea MS |
1352 | <h4 class="constants">Constants</h4> |
1353 | <dl> | |
1354 | <dt>CUPS_SC_BIDI_NOT_SUPPORTED </dt> | |
1355 | <dd class="description">Bidirectional I/O is not supported</dd> | |
1356 | <dt>CUPS_SC_BIDI_SUPPORTED </dt> | |
1357 | <dd class="description">Bidirectional I/O is supported</dd> | |
1358 | </dl> | |
1359 | <h3 class="enumeration"><a name="cups_sc_command_e">cups_sc_command_e</a></h3> | |
1360 | <p class="description">Request command codes</p> | |
1361 | <h4 class="constants">Constants</h4> | |
1362 | <dl> | |
1363 | <dt>CUPS_SC_CMD_DRAIN_OUTPUT </dt> | |
1364 | <dd class="description">Drain all pending output</dd> | |
1365 | <dt>CUPS_SC_CMD_GET_BIDI </dt> | |
1366 | <dd class="description">Return bidirectional capabilities</dd> | |
1367 | <dt>CUPS_SC_CMD_GET_DEVICE_ID </dt> | |
1368 | <dd class="description">Return the IEEE-1284 device ID</dd> | |
1369 | <dt>CUPS_SC_CMD_GET_STATE </dt> | |
1370 | <dd class="description">Return the device state</dd> | |
178cb736 | 1371 | <dt>CUPS_SC_CMD_SNMP_GET <span class="info"> CUPS 1.4/Mac OS X 10.6 </span></dt> |
20fbc903 | 1372 | <dd class="description">Query an SNMP OID </dd> |
178cb736 | 1373 | <dt>CUPS_SC_CMD_SNMP_GET_NEXT <span class="info"> CUPS 1.4/Mac OS X 10.6 </span></dt> |
20fbc903 | 1374 | <dd class="description">Query the next SNMP OID </dd> |
5a738aea MS |
1375 | <dt>CUPS_SC_CMD_SOFT_RESET </dt> |
1376 | <dd class="description">Do a soft reset</dd> | |
1377 | </dl> | |
1378 | <h3 class="enumeration"><a name="cups_sc_state_e">cups_sc_state_e</a></h3> | |
1379 | <p class="description">Printer state bits</p> | |
1380 | <h4 class="constants">Constants</h4> | |
1381 | <dl> | |
1382 | <dt>CUPS_SC_STATE_BUSY </dt> | |
1383 | <dd class="description">Device is busy</dd> | |
1384 | <dt>CUPS_SC_STATE_ERROR </dt> | |
1385 | <dd class="description">Other error condition</dd> | |
1386 | <dt>CUPS_SC_STATE_MARKER_EMPTY </dt> | |
1387 | <dd class="description">Toner/ink out condition</dd> | |
1388 | <dt>CUPS_SC_STATE_MARKER_LOW </dt> | |
1389 | <dd class="description">Toner/ink low condition</dd> | |
1390 | <dt>CUPS_SC_STATE_MEDIA_EMPTY </dt> | |
1391 | <dd class="description">Paper out condition</dd> | |
1392 | <dt>CUPS_SC_STATE_MEDIA_LOW </dt> | |
1393 | <dd class="description">Paper low condition</dd> | |
1394 | <dt>CUPS_SC_STATE_OFFLINE </dt> | |
79e1d494 | 1395 | <dd class="description">Device is offline</dd> |
5a738aea | 1396 | <dt>CUPS_SC_STATE_ONLINE </dt> |
79e1d494 | 1397 | <dd class="description">Device is online</dd> |
5a738aea MS |
1398 | </dl> |
1399 | <h3 class="enumeration"><a name="cups_sc_status_e">cups_sc_status_e</a></h3> | |
1400 | <p class="description">Response status codes</p> | |
1401 | <h4 class="constants">Constants</h4> | |
1402 | <dl> | |
1403 | <dt>CUPS_SC_STATUS_BAD_MESSAGE </dt> | |
1404 | <dd class="description">The command/response message was invalid</dd> | |
1405 | <dt>CUPS_SC_STATUS_IO_ERROR </dt> | |
1406 | <dd class="description">An I/O error occurred</dd> | |
1407 | <dt>CUPS_SC_STATUS_NONE </dt> | |
1408 | <dd class="description">No status</dd> | |
1409 | <dt>CUPS_SC_STATUS_NOT_IMPLEMENTED </dt> | |
1410 | <dd class="description">Command not implemented</dd> | |
1411 | <dt>CUPS_SC_STATUS_NO_RESPONSE </dt> | |
1412 | <dd class="description">The device did not respond</dd> | |
1413 | <dt>CUPS_SC_STATUS_OK </dt> | |
1414 | <dd class="description">Operation succeeded</dd> | |
1415 | <dt>CUPS_SC_STATUS_TIMEOUT </dt> | |
1416 | <dd class="description">The backend did not respond</dd> | |
1417 | <dt>CUPS_SC_STATUS_TOO_BIG </dt> | |
1418 | <dd class="description">Response too big</dd> | |
1419 | </dl> | |
1420 | </div> | |
ef416fc2 | 1421 | </body> |
1422 | </html> |