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341 "$Id: api-filter.header 8627 2009-05-13 21:39:17Z mike $"
343 Filter and backend programming header for the Common UNIX Printing System
346 Copyright 2008-2009 by Apple Inc.
348 These coded instructions, statements, and computer programs are the
349 property of Apple Inc. and are protected by Federal copyright
350 law. Distribution and use rights are outlined in the file "LICENSE.txt"
351 which should have been included with this file. If this file is
352 file is missing or damaged, see the license at "http://www.cups.org/".
355 <h1 class='title'
>Filter and Backend Programming
</h1>
357 <div class='summary'
><table summary='General Information'
>
361 <th>cups/backend.h
<br>
362 cups/sidechannel.h
</th>
372 <td>Programming:
<a href='api-overview.html' target='_top'
>Introduction to CUPS Programming
</a><br>
373 Programming:
<a href='api-cups.html' target='_top'
>CUPS API
</a><br>
374 Programming:
<a href='api-ppd.html' target='_top'
>PPD API
</a><br>
375 Programming:
<a href='api-raster.html' target='_top'
>Raster API
</a><br>
376 Specifications:
<a href='spec-design' target='_top'
>CUPS Design Description
</a></td>
380 <h2 class=
"title">Contents
</h2>
381 <ul class=
"contents">
382 <ul class=
"subcontents">
383 <li><a href=
"#OVERVIEW">Overview
</a><ul class=
"subcontents">
384 <li><a href=
"#SECURITY">Security Considerations
</a></li>
385 <li><a href=
"#PERMISSIONS">File Permissions
</a></li>
386 <li><a href=
"#TEMPFILES">Temporary Files
</a></li>
387 <li><a href=
"#COPIES">Copy Generation
</a></li>
388 <li><a href=
"#EXITCODES">Exit Codes
</a></li>
389 <li><a href=
"#ENVIRONMENT">Environment Variables
</a></li>
390 <li><a href=
"#MESSAGES">Communicating with the Scheduler
</a></li>
391 <li><a href=
"#COMMUNICATING_BACKEND">Communicating with the Backend
</a></li>
392 <li><a href=
"#COMMUNICATING_FILTER">Communicating with Filters
</a></li>
393 <li><a href=
"#SNMP">Doing SNMP Queries with Network Printers
</a></li>
395 <li><a href=
"#FUNCTIONS">Functions
</a><ul class=
"code">
396 <li><a href=
"#cupsBackChannelRead" title=
"Read data from the backchannel.">cupsBackChannelRead
</a></li>
397 <li><a href=
"#cupsBackChannelWrite" title=
"Write data to the backchannel.">cupsBackChannelWrite
</a></li>
398 <li><a href=
"#cupsBackendDeviceURI" title=
"Get the device URI for a backend.">cupsBackendDeviceURI
</a></li>
399 <li><a href=
"#cupsBackendReport" title=
"Write a device line from a backend.">cupsBackendReport
</a></li>
400 <li><a href=
"#cupsSideChannelDoRequest" title=
"Send a side-channel command to a backend and wait for a response.">cupsSideChannelDoRequest
</a></li>
401 <li><a href=
"#cupsSideChannelRead" title=
"Read a side-channel message.">cupsSideChannelRead
</a></li>
402 <li><a href=
"#cupsSideChannelSNMPGet" title=
"Query a SNMP OID's value.">cupsSideChannelSNMPGet
</a></li>
403 <li><a href=
"#cupsSideChannelSNMPWalk" title=
"Query multiple SNMP OID values.">cupsSideChannelSNMPWalk
</a></li>
404 <li><a href=
"#cupsSideChannelWrite" title=
"Write a side-channel message.">cupsSideChannelWrite
</a></li>
406 <li><a href=
"#TYPES">Data Types
</a><ul class=
"code">
407 <li><a href=
"#cups_backend_t" title=
"Backend exit codes">cups_backend_t
</a></li>
408 <li><a href=
"#cups_sc_bidi_t" title=
"Bidirectional capabilities">cups_sc_bidi_t
</a></li>
409 <li><a href=
"#cups_sc_command_t" title=
"Request command codes">cups_sc_command_t
</a></li>
410 <li><a href=
"#cups_sc_state_t" title=
"Printer state bits">cups_sc_state_t
</a></li>
411 <li><a href=
"#cups_sc_status_t" title=
"Response status codes">cups_sc_status_t
</a></li>
412 <li><a href=
"#cups_sc_walk_func_t" title=
"SNMP walk callback">cups_sc_walk_func_t
</a></li>
414 <li><a href=
"#ENUMERATIONS">Constants
</a><ul class=
"code">
415 <li><a href=
"#cups_backend_e" title=
"Backend exit codes">cups_backend_e
</a></li>
416 <li><a href=
"#cups_sc_bidi_e" title=
"Bidirectional capability values">cups_sc_bidi_e
</a></li>
417 <li><a href=
"#cups_sc_command_e" title=
"Request command codes">cups_sc_command_e
</a></li>
418 <li><a href=
"#cups_sc_state_e" title=
"Printer state bits">cups_sc_state_e
</a></li>
419 <li><a href=
"#cups_sc_status_e" title=
"Response status codes">cups_sc_status_e
</a></li>
422 "$Id: api-filter.shtml 7962 2008-09-18 17:31:33Z mike $"
424 Filter and backend programming introduction for the Common UNIX Printing
427 Copyright 2007-2009 by Apple Inc.
428 Copyright 1997-2006 by Easy Software Products, all rights reserved.
430 These coded instructions, statements, and computer programs are the
431 property of Apple Inc. and are protected by Federal copyright
432 law. Distribution and use rights are outlined in the file "LICENSE.txt"
433 which should have been included with this file. If this file is
434 file is missing or damaged, see the license at "http://www.cups.org/".
437 <h2 class='title'
><a name=
"OVERVIEW">Overview
</a></h2>
439 <p>Filters (which include printer drivers and port monitors) and backends
440 are used to convert job files to a printable format and send that data to the
441 printer itself. All of these programs use a common interface for processing
442 print jobs and communicating status information to the scheduler. Each is run
443 with a standard set of command-line arguments:
<p>
451 <dd>The user printing the job
</dd>
454 <dd>The job name/title
</dd>
457 <dd>The number of copies to print
</dd>
460 <dd>The options that were provided when the job was submitted
</dd>
463 <dd>The file to print (first program only)
</dd>
466 <p>The scheduler runs one or more of these programs to print any given job. The
467 first filter reads from the print file and writes to the standard output, while
468 the remaining filters read from the standard input and write to the standard
469 output. The backend is the last filter in the chain and writes to the
472 <p>Filters are always run as a non-privileged user, typically
"lp", with no
473 connection to the user's desktop. Backends are run either as a non-privileged
474 user or as root if the file permissions do not allow user or group execution.
475 The
<a href=
"#PERMISSIONS">file permissions
</a> section talks about this in
478 <h3><a name=
"SECURITY">Security Considerations
</a></h3>
480 <p>It is always important to use security programming practices. Filters and
481 most backends are run as a non-priviledged user, so the major security
482 consideration is resource utilization - filters should not depend on unlimited
483 amounts of CPU, memory, or disk space, and should protect against conditions
484 that could lead to excess usage of any resource like infinite loops and
485 unbounded recursion. In addition, filters must
<em>never
</em> allow the user to
486 specify an arbitrary file path to a separator page, template, or other file
487 used by the filter since that can lead to an unauthorized disclosure of
488 information.
<em>Always
</em> treat input as suspect and validate it!
</p>
490 <p>If you are developing a backend that runs as root , make sure to check for
491 potential buffer overflows, integer under/overflow conditions, and file
492 accesses since these can lead to privilege escalations. When writing files,
493 always validate the file path and
<em>never
</em> allow a user to determine
494 where to store a file.
</p>
496 <blockquote><b>Note:
</b>
498 <p><em>Never
</em> write files to a user's home directory. Aside from the
499 security implications, CUPS is a network print service and as such the network
500 user may not be the same as the local user and/or there may not be a local home
501 directory to write to.
</p>
503 <p>In addition, some operating systems provide additional security mechanisms
504 that further limit file system access, even for backends running as root. On
505 Mac OS X, for example, no backend may write to a user's home directory.
</p>
508 <h3><a name=
"PERMISSIONS">File Permissions
</a></h3>
510 <p>For security reasons, CUPS will only run filters and backends that are owned
511 by root and do not have world write permissions. The recommended permissions for
512 filters and backends are
0555 - read and execute but no write. Backends that
513 must run as root should use permissions of
0500 - read and execute by root, no
514 access for other users. Write permissions can be enabled for the root user
517 <p>To avoid a warning message, the directory containing your filter(s) must also
518 be owned by root and have world write disabled - permissions of
0755 or
0555 are
519 strongly encouraged.
</p>
521 <h3><a name=
"TEMPFILES">Temporary Files
</a></h3>
523 <p>Temporary files should be created in the directory specified by the
524 "TMPDIR" environment variable. The
525 <a href=
"#cupsTempFile2"><code>cupsTempFile2
</code></a> function can be
526 used to safely create temporary files in this directory.
</p>
528 <h3><a name=
"COPIES">Copy Generation
</a></h3>
530 <p>The
<code>argv[
4]
</code> argument specifies the number of copies to produce
531 of the input file. In general, you should only generate copies if the
532 <em>filename
</em> argument is supplied. The only exception to this are
533 filters that produce device-independent PostScript output, since the PostScript
534 filter
<var>pstops
</var> is responsible for generating copies of PostScript
537 <h3><a name=
"EXITCODES">Exit Codes
</a></h3>
539 <p>Filters must exit with status
0 when they successfully generate print data
540 or
1 when they encounter an error. Backends can return any of the
541 <a href=
"#cups_backend_t"><code>cups_backend_t
</code></a> constants.
</p>
543 <h3><a name=
"ENVIRONMENT">Environment Variables
</a></h3>
545 <p>The following environment variables are defined by the printing system
546 when running print filters and backends:
</p>
550 <dt>APPLE_LANGUAGES
</dt>
551 <dd>The Apple language identifier associated with the job
552 (Mac OS X only).
</dd>
555 <dd>The job character set, typically
"utf-8".
</dd>
558 <dd>When a job is submitted to a printer class, contains the name of
559 the destination printer class. Otherwise this environment
560 variable will not be set.
</dd>
562 <dt>CONTENT_TYPE
</dt>
563 <dd>The MIME type associated with the file (e.g.
564 application/postscript).
</dd>
566 <dt>CUPS_CACHEDIR
</dt>
567 <dd>The directory where cache files can be stored. Cache files can be
568 used to retain information between jobs or files in a job.
</dd>
570 <dt>CUPS_DATADIR
</dt>
571 <dd>The directory where (read-only) CUPS data files can be found.
</dd>
573 <dt>CUPS_FILETYPE
</dt>
574 <dd>The type of file being printed:
"job-sheet" for a banner page and
575 "document" for a regular print file.
</dd>
577 <dt>CUPS_SERVERROOT
</dt>
578 <dd>The root directory of the server.
</dd>
581 <dd>The device-uri associated with the printer.
</dd>
583 <dt>FINAL_CONTENT_TYPE
</dt>
584 <dd>The MIME type associated with the printer (e.g.
585 application/vnd.cups-postscript).
</dd>
588 <dd>The language locale associated with the job.
</dd>
591 <dd>The full pathname of the PostScript Printer Description (PPD)
592 file for this printer.
</dd>
595 <dd>The queue name of the class or printer.
</dd>
598 <dd>The recommended amount of memory to use for Raster Image
599 Processors (RIPs).
</dd>
602 <dd>The directory where temporary files should be created.
</dd>
606 <h3><a name=
"MESSAGES">Communicating with the Scheduler
</a></h3>
608 <p>Filters and backends communicate with the scheduler by writing messages
609 to the standard error file. The scheduler reads messages from all filters in
610 a job and processes the message based on its prefix. For example, the following
611 code sets the current printer state message to
"Printing page 5":
</p>
613 <pre class=
"example">
616 fprintf(stderr,
"INFO: Printing page %d\n", page);
619 <p>Each message is a single line of text starting with one of the following
624 <dt>ALERT: message
</dt>
625 <dd>Sets the printer-state-message attribute and adds the specified
626 message to the current error log file using the
"alert" log level.
</dd>
628 <dt>ATTR: attribute=value [attribute=value]
</dt>
629 <dd>Sets the named printer or job attribute(s). Typically this is used
630 to set the
<code>marker-colors
</code>,
<code>marker-levels
</code>,
631 <code>marker-message
</code>,
<code>marker-names
</code>,
632 <code>marker-types
</code>,
<code>printer-alert
</code>, and
633 <code>printer-alert-description
</code> printer attributes. Standard
634 <code>marker-types
</code> values are listed in
<a href='#TABLE1'
>Table
637 <dt>CRIT: message
</dt>
638 <dd>Sets the printer-state-message attribute and adds the specified
639 message to the current error log file using the
"critical" log
642 <dt>DEBUG: message
</dt>
643 <dd>Sets the printer-state-message attribute and adds the specified
644 message to the current error log file using the
"debug" log level.
</dd>
646 <dt>DEBUG2: message
</dt>
647 <dd>Sets the printer-state-message attribute and adds the specified
648 message to the current error log file using the
"debug2" log level.
</dd>
650 <dt>EMERG: message
</dt>
651 <dd>Sets the printer-state-message attribute and adds the specified
652 message to the current error log file using the
"emergency" log
655 <dt>ERROR: message
</dt>
656 <dd>Sets the printer-state-message attribute and adds the specified
657 message to the current error log file using the
"error" log level.
658 Use
"ERROR:" messages for non-persistent processing errors.
</dd>
660 <dt>INFO: message
</dt>
661 <dd>Sets the printer-state-message attribute. If the current log level
662 is set to
"debug2", also adds the specified message to the current error
663 log file using the
"info" log level.
</dd>
665 <dt>NOTICE: message
</dt>
666 <dd>Sets the printer-state-message attribute and adds the specified
667 message to the current error log file using the
"notice" log level.
</dd>
669 <dt>PAGE: page-number #-copies
</dt>
670 <dt>PAGE: total #-pages
</dt>
671 <dd>Adds an entry to the current page log file. The first form adds
672 #-copies to the job-media-sheets-completed attribute. The second
673 form sets the job-media-sheets-completed attribute to #-pages.
</dd>
675 <dt>PPD: keyword=value [keyword=value ...]
</dt>
676 <dd>Changes or adds keywords to the printer's PPD file. Typically
677 this is used to update installable options or default media settings
678 based on the printer configuration.
</dd>
680 <dt>STATE: printer-state-reason [printer-state-reason ...]
</dt>
681 <dt>STATE: + printer-state-reason [printer-state-reason ...]
</dt>
682 <dt>STATE: - printer-state-reason [printer-state-reason ...]
</dt>
683 <dd>Sets, adds, or removes printer-state-reason keywords to the
684 current queue. Typically this is used to indicate persistent media,
685 ink, toner, and configuration conditions or errors on a printer.
686 <a href='#TABLE2'
>Table
2</a> lists the standard state keywords -
687 use vendor-prefixed (
"com.acme.foo") keywords for custom states.
</dd>
689 <dt>WARNING: message
</dt>
690 <dd>Sets the printer-state-message attribute and adds the specified
691 message to the current error log file using the
"warning" log
696 <p>Messages without one of these prefixes are treated as if they began with
697 the
"DEBUG:" prefix string.
</p>
700 <div class='table'
><table width='
80%' summary='Table
1: Standard marker-types Values'
>
701 <caption>Table
1:
<a name='TABLE1'
>Standard marker-types Values
</a></caption>
711 <td>Developer unit
</td>
718 <td>fuserCleaningPad
</td>
719 <td>Fuser cleaning pad
</td>
731 <td>Photo conductor
</td>
739 <td>Staple supply
</td>
743 <td>Toner supply
</td>
746 <td>transferUnit
</td>
747 <td>Transfer unit
</td>
751 <td>Waste ink tank
</td>
755 <td>Waste toner tank
</td>
759 <td>Waste wax tank
</td>
766 <div class='table'
><table width='
80%' summary='Table
2: Standard State Keywords'
>
767 <caption>Table
2:
<a name='TABLE2'
>Standard State Keywords
</a></caption>
776 <td>connecting-to-device
</td>
777 <td>Connecting to printer but not printing yet
</td>
781 <td>A cover is open on the printer
</td>
784 <td>input-tray-missing
</td>
785 <td>An input tray is missing from the printer
</td>
788 <td>marker-supply-empty
</td>
792 <td>marker-supply-low
</td>
796 <td>marker-waste-almost-full
</td>
797 <td>Waste tank almost full
</td>
800 <td>marker-waste-full
</td>
801 <td>Waste tank full
</td>
805 <td>Out of media
</td>
809 <td>Media is jammed in the printer
</td>
813 <td>Low on media
</td>
817 <td>Stop the printer
</td>
821 <td>Unable to connect to printer
</td>
825 <td>Out of toner
</td>
829 <td>Low on toner
</td>
834 <h3><a name=
"COMMUNICATING_BACKEND">Communicating with the Backend
</a></h3>
836 <p>Filters can communicate with the backend via the
837 <a href=
"#cupsBackChannelRead"><code>cupsBackChannelRead
</code></a> and
838 <a href=
"#cupsSideChannelDoRequest"><code>cupsSideChannelDoRequest
</code></a>
840 <a href=
"#cupsBackChannelRead"><code>cupsBackChannelRead
</code></a> function
841 reads data that has been sent back from the device and is typically used to
842 obtain status and configuration information. For example, the following code
843 polls the backend for back-channel data:
</p>
845 <pre class=
"example">
846 #include
<cups/cups.h
>
851 /* Use a timeout of
0.0 seconds to poll for back-channel data */
852 bytes = cupsBackChannelRead(buffer, sizeof(buffer),
0.0);
855 <p>Filters can also use
<code>select()
</code> or
<code>poll()
</code> on the
856 back-channel file descriptor (
3 or
<code>CUPS_BC_FD
</code>) to read data only
857 when it is available.
</p>
860 <a href=
"#cupsSideChannelDoRequest"><code>cupsSideChannelDoRequest
</code></a>
861 function allows you to get out-of-band status information and do synchronization
862 with the device. For example, the following code gets the current IEEE-
1284
863 device ID string from the backend:
</p>
865 <pre class=
"example">
866 #include
<cups/sidechannel.h
>
870 <a href=
"#cups_sc_status_t">cups_sc_status_t
</a> status;
872 /* Tell cupsSideChannelDoRequest() how big our buffer is, less
1 byte for
873 nul-termination... */
874 datalen = sizeof(data) -
1;
876 /* Get the IEEE-
1284 device ID, waiting for up to
1 second */
877 status =
<a href=
"#cupsSideChannelDoRequest">cupsSideChannelDoRequest
</a>(CUPS_SC_CMD_GET_DEVICE_ID, data,
&datalen,
1.0);
879 /* Use the returned value if OK was returned and the length is non-zero */
880 if (status == CUPS_SC_STATUS_OK && datalen
> 0)
881 data[datalen] = '\
0';
886 <h3><a name=
"COMMUNICATING_FILTER">Communicating with Filters
</a></h3>
888 <p>Backends communicate with filters using the reciprocal functions
889 <a href=
"#cupsBackChannelWrite"><code>cupsBackChannelWrite
</code></a>,
890 <a href=
"#cupsSideChannelRead"><code>cupsSideChannelRead
</code></a>, and
891 <a href=
"#cupsSideChannelWrite"><code>cupsSideChannelWrite
</code></a>. We
892 recommend writing back-channel data using a timeout of
1.0 seconds:
</p>
894 <pre class=
"example">
895 #include
<cups/cups.h
>
900 /* Obtain data from printer/device */
903 /* Use a timeout of
1.0 seconds to give filters a chance to read */
904 cupsBackChannelWrite(buffer, bytes,
1.0);
907 <p>The
<a href=
"#cupsSideChannelRead"><code>cupsSideChannelRead
</code></a>
908 function reads a side-channel command from a filter, driver, or port monitor.
909 Backends can either poll for commands using a
<code>timeout
</code> of
0.0, wait
910 indefinitely for commands using a
<code>timeout
</code> of -
1.0 (probably in a
911 separate thread for that purpose), or use
<code>select
</code> or
912 <code>poll
</code> on the
<code>CUPS_SC_FD
</code> file descriptor (
4) to handle
913 input and output on several file descriptors at the same time.
</p>
915 <p>Once a command is processed, the backend uses the
916 <a href=
"#cupsSideChannelWrite"><code>cupsSideChannelWrite
</code></a> function
917 to send its response. For example, the following code shows how to poll for a
918 side-channel command and respond to it:
</p>
920 <pre class=
"example">
921 #include
<cups/sidechannel.h
>
923 <a href=
"#cups_sc_command_t">cups_sc_command_t
</a> command;
924 <a href=
"#cups_sc_status_t">cups_sc_status_t
</a> status;
926 int datalen = sizeof(data);
928 /* Poll for a command... */
929 if (!
<a href=
"#cupsSideChannelRead">cupsSideChannelRead
</a>(
&command,
&status, data,
&datalen,
0.0))
933 /* handle supported commands, fill data/datalen/status with values as needed */
936 status = CUPS_SC_STATUS_NOT_IMPLEMENTED;
941 /* Send a response... */
942 <a href=
"#cupsSideChannelWrite">cupsSideChannelWrite
</a>(command, status, data, datalen,
1.0);
946 <h3><a name=
"SNMP">Doing SNMP Queries with Network Printers
</a></h3>
948 <p>The Simple Network Management Protocol (SNMP) allows you to get the current
949 status, page counter, and supply levels from most network printers. Every
950 piece of information is associated with an Object Identifier (OID), and
951 every printer has a
<em>community
</em> name associated with it. OIDs can be
952 queried directly or by
"walking" over a range of OIDs with a common prefix.
</p>
954 <p>The two CUPS SNMP functions provide a simple API for querying network
955 printers through the side-channel interface. Each accepts a string containing
956 an OID like
".1.3.6.1.2.1.43.10.2.1.4.1.1" (the standard page counter OID)
957 along with a timeout for the query.
</p>
959 <p>The
<a href=
"#cupsSideChannelSNMPGet"><code>cupsSideChannelSNMPGet
</code></a>
960 function queries a single OID and returns the value as a string in a buffer
963 <pre class=
"example">
964 #include
<cups/sidechannel.h
>
967 int datalen = sizeof(data);
969 if (
<a href=
"#cupsSideChannelSNMPGet">cupsSideChannelSNMPGet
</a>(
".1.3.6.1.2.1.43.10.2.1.4.1.1", data,
&datalen,
5.0)
970 == CUPS_SC_STATUS_OK)
972 /* Do something with the value */
973 printf(
"Page counter is: %s\n", data);
978 <a href=
"#cupsSideChannelSNMPWalk"><code>cupsSideChannelSNMPWalk
</code></a>
979 function allows you to query a whole group of OIDs, calling a function of your
980 choice for each OID that is found:
</p>
982 <pre class=
"example">
983 #include
<cups/sidechannel.h
>
986 my_callback(const char *oid, const char *data, int datalen, void *context)
988 /* Do something with the value */
989 printf(
"%s=%s\n", oid, data);
996 <a href=
"#cupsSideChannelSNMPWalk">cupsSNMPSideChannelWalk
</a>(
".1.3.6.1.2.1.43",
5.0, my_callback, my_data);
998 <h2 class=
"title"><a name=
"FUNCTIONS">Functions
</a></h2>
999 <h3 class=
"function"><span class=
"info"> CUPS
1.2/Mac OS X
10.5 </span><a name=
"cupsBackChannelRead">cupsBackChannelRead
</a></h3>
1000 <p class=
"description">Read data from the backchannel.
</p>
1002 ssize_t cupsBackChannelRead (
<br>
1003 char *buffer,
<br>
1004 size_t bytes,
<br>
1005 double timeout
<br>
1007 <h4 class=
"parameters">Parameters
</h4>
1010 <dd class=
"description">Buffer to read into
</dd>
1012 <dd class=
"description">Bytes to read
</dd>
1014 <dd class=
"description">Timeout in seconds, typically
0.0 to poll
</dd>
1016 <h4 class=
"returnvalue">Return Value
</h4>
1017 <p class=
"description">Bytes read or -
1 on error
</p>
1018 <h4 class=
"discussion">Discussion
</h4>
1019 <p class=
"discussion">Reads up to
"bytes
" bytes from the backchannel/backend. The
"timeout
"
1020 parameter controls how many seconds to wait for the data - use
0.0 to
1021 return immediately if there is no data, -
1.0 to wait for data indefinitely.
1024 <h3 class=
"function"><span class=
"info"> CUPS
1.2/Mac OS X
10.5 </span><a name=
"cupsBackChannelWrite">cupsBackChannelWrite
</a></h3>
1025 <p class=
"description">Write data to the backchannel.
</p>
1027 ssize_t cupsBackChannelWrite (
<br>
1028 const char *buffer,
<br>
1029 size_t bytes,
<br>
1030 double timeout
<br>
1032 <h4 class=
"parameters">Parameters
</h4>
1035 <dd class=
"description">Buffer to write
</dd>
1037 <dd class=
"description">Bytes to write
</dd>
1039 <dd class=
"description">Timeout in seconds, typically
1.0</dd>
1041 <h4 class=
"returnvalue">Return Value
</h4>
1042 <p class=
"description">Bytes written or -
1 on error
</p>
1043 <h4 class=
"discussion">Discussion
</h4>
1044 <p class=
"discussion">Writes
"bytes
" bytes to the backchannel/filter. The
"timeout
" parameter
1045 controls how many seconds to wait for the data to be written - use
1046 0.0 to return immediately if the data cannot be written, -
1.0 to wait
1050 <h3 class=
"function"><span class=
"info"> CUPS
1.2/Mac OS X
10.5 </span><a name=
"cupsBackendDeviceURI">cupsBackendDeviceURI
</a></h3>
1051 <p class=
"description">Get the device URI for a backend.
</p>
1053 const char *cupsBackendDeviceURI (
<br>
1054 char **argv
<br>
1056 <h4 class=
"parameters">Parameters
</h4>
1059 <dd class=
"description">Command-line arguments
</dd>
1061 <h4 class=
"returnvalue">Return Value
</h4>
1062 <p class=
"description">Device URI or
<code>NULL
</code></p>
1063 <h4 class=
"discussion">Discussion
</h4>
1064 <p class=
"discussion">The
"argv
" argument is the argv argument passed to main(). This
1065 function returns the device URI passed in the DEVICE_URI environment
1066 variable or the device URI passed in argv[
0], whichever is found
1070 <h3 class=
"function"><span class=
"info"> CUPS
1.4/Mac OS X
10.6 </span><a name=
"cupsBackendReport">cupsBackendReport
</a></h3>
1071 <p class=
"description">Write a device line from a backend.
</p>
1073 void cupsBackendReport (
<br>
1074 const char *device_scheme,
<br>
1075 const char *device_uri,
<br>
1076 const char *device_make_and_model,
<br>
1077 const char *device_info,
<br>
1078 const char *device_id,
<br>
1079 const char *device_location
<br>
1081 <h4 class=
"parameters">Parameters
</h4>
1083 <dt>device_scheme
</dt>
1084 <dd class=
"description">device-scheme string
</dd>
1086 <dd class=
"description">device-uri string
</dd>
1087 <dt>device_make_and_model
</dt>
1088 <dd class=
"description">device-make-and-model string or
<code>NULL
</code></dd>
1089 <dt>device_info
</dt>
1090 <dd class=
"description">device-info string or
<code>NULL
</code></dd>
1092 <dd class=
"description">device-id string or
<code>NULL
</code></dd>
1093 <dt>device_location
</dt>
1094 <dd class=
"description">device-location string or
<code>NULL
</code></dd>
1096 <h4 class=
"discussion">Discussion
</h4>
1097 <p class=
"discussion">This function writes a single device line to stdout for a backend.
1098 It handles quoting of special characters in the device-make-and-model,
1099 device-info, device-id, and device-location strings.
1102 <h3 class=
"function"><span class=
"info"> CUPS
1.3/Mac OS X
10.5 </span><a name=
"cupsSideChannelDoRequest">cupsSideChannelDoRequest
</a></h3>
1103 <p class=
"description">Send a side-channel command to a backend and wait for a response.
</p>
1105 <a href=
"#cups_sc_status_t">cups_sc_status_t
</a> cupsSideChannelDoRequest (
<br>
1106 <a href=
"#cups_sc_command_t">cups_sc_command_t
</a> command,
<br>
1107 char *data,
<br>
1108 int *datalen,
<br>
1109 double timeout
<br>
1111 <h4 class=
"parameters">Parameters
</h4>
1114 <dd class=
"description">Command to send
</dd>
1116 <dd class=
"description">Response data buffer pointer
</dd>
1118 <dd class=
"description">Size of data buffer on entry, number of bytes in buffer on return
</dd>
1120 <dd class=
"description">Timeout in seconds
</dd>
1122 <h4 class=
"returnvalue">Return Value
</h4>
1123 <p class=
"description">Status of command
</p>
1124 <h4 class=
"discussion">Discussion
</h4>
1125 <p class=
"discussion">This function is normally only called by filters, drivers, or port
1126 monitors in order to communicate with the backend used by the current
1127 printer. Programs must be prepared to handle timeout or
"not
1128 implemented
" status codes, which indicate that the backend or device
1129 do not support the specified side-channel command.
<br>
1131 The
"datalen
" parameter must be initialized to the size of the buffer
1132 pointed to by the
"data
" parameter. cupsSideChannelDoRequest() will
1133 update the value to contain the number of data bytes in the buffer.
1136 <h3 class=
"function"><span class=
"info"> CUPS
1.3/Mac OS X
10.5 </span><a name=
"cupsSideChannelRead">cupsSideChannelRead
</a></h3>
1137 <p class=
"description">Read a side-channel message.
</p>
1139 int cupsSideChannelRead (
<br>
1140 <a href=
"#cups_sc_command_t">cups_sc_command_t
</a> *command,
<br>
1141 <a href=
"#cups_sc_status_t">cups_sc_status_t
</a> *status,
<br>
1142 char *data,
<br>
1143 int *datalen,
<br>
1144 double timeout
<br>
1146 <h4 class=
"parameters">Parameters
</h4>
1149 <dd class=
"description">Command code
</dd>
1151 <dd class=
"description">Status code
</dd>
1153 <dd class=
"description">Data buffer pointer
</dd>
1155 <dd class=
"description">Size of data buffer on entry, number of bytes in buffer on return
</dd>
1157 <dd class=
"description">Timeout in seconds
</dd>
1159 <h4 class=
"returnvalue">Return Value
</h4>
1160 <p class=
"description">0 on success, -
1 on error
</p>
1161 <h4 class=
"discussion">Discussion
</h4>
1162 <p class=
"discussion">This function is normally only called by backend programs to read
1163 commands from a filter, driver, or port monitor program. The
1164 caller must be prepared to handle incomplete or invalid messages
1165 and return the corresponding status codes.
<br>
1167 The
"datalen
" parameter must be initialized to the size of the buffer
1168 pointed to by the
"data
" parameter. cupsSideChannelDoRequest() will
1169 update the value to contain the number of data bytes in the buffer.
1172 <h3 class=
"function"><span class=
"info"> CUPS
1.4/Mac OS X
10.6 </span><a name=
"cupsSideChannelSNMPGet">cupsSideChannelSNMPGet
</a></h3>
1173 <p class=
"description">Query a SNMP OID's value.
</p>
1175 <a href=
"#cups_sc_status_t">cups_sc_status_t
</a> cupsSideChannelSNMPGet (
<br>
1176 const char *oid,
<br>
1177 char *data,
<br>
1178 int *datalen,
<br>
1179 double timeout
<br>
1181 <h4 class=
"parameters">Parameters
</h4>
1184 <dd class=
"description">OID to query
</dd>
1186 <dd class=
"description">Buffer for OID value
</dd>
1188 <dd class=
"description">Size of OID buffer on entry, size of value on return
</dd>
1190 <dd class=
"description">Timeout in seconds
</dd>
1192 <h4 class=
"returnvalue">Return Value
</h4>
1193 <p class=
"description">Query status
</p>
1194 <h4 class=
"discussion">Discussion
</h4>
1195 <p class=
"discussion">This function asks the backend to do a SNMP OID query on behalf of the
1196 filter, port monitor, or backend using the default community name.
<br>
1198 "oid
" contains a numeric OID consisting of integers separated by periods,
1199 for example
".1.3.6.1.2.1.43". Symbolic names from SNMP MIBs are not
1200 supported and must be converted to their numeric forms.
<br>
1202 On input,
"data
" and
"datalen
" provide the location and size of the
1203 buffer to hold the OID value as a string. HEX-String (binary) values are
1204 converted to hexadecimal strings representing the binary data, while
1205 NULL-Value and unknown OID types are returned as the empty string.
1206 The returned
"datalen
" does not include the trailing nul.
1208 <code>CUPS_SC_STATUS_NOT_IMPLEMENTED
</code> is returned by backends that do not
1209 support SNMP queries.
<code>CUPS_SC_STATUS_NO_RESPONSE
</code> is returned when
1210 the printer does not respond to the SNMP query.
1213 <h3 class=
"function"><span class=
"info"> CUPS
1.4/Mac OS X
10.6 </span><a name=
"cupsSideChannelSNMPWalk">cupsSideChannelSNMPWalk
</a></h3>
1214 <p class=
"description">Query multiple SNMP OID values.
</p>
1216 <a href=
"#cups_sc_status_t">cups_sc_status_t
</a> cupsSideChannelSNMPWalk (
<br>
1217 const char *oid,
<br>
1218 double timeout,
<br>
1219 <a href=
"#cups_sc_walk_func_t">cups_sc_walk_func_t
</a> cb,
<br>
1220 void *context
<br>
1222 <h4 class=
"parameters">Parameters
</h4>
1225 <dd class=
"description">First numeric OID to query
</dd>
1227 <dd class=
"description">Timeout for each query in seconds
</dd>
1229 <dd class=
"description">Function to call with each value
</dd>
1231 <dd class=
"description">Application-defined pointer to send to callback
</dd>
1233 <h4 class=
"returnvalue">Return Value
</h4>
1234 <p class=
"description">Status of first query of
<code>CUPS_SC_STATUS_OK
</code> on success
</p>
1235 <h4 class=
"discussion">Discussion
</h4>
1236 <p class=
"discussion">This function asks the backend to do multiple SNMP OID queries on behalf
1237 of the filter, port monitor, or backend using the default community name.
1238 All OIDs under the
"parent
" OID are queried and the results are sent to
1239 the callback function you provide.
<br>
1241 "oid
" contains a numeric OID consisting of integers separated by periods,
1242 for example
".1.3.6.1.2.1.43". Symbolic names from SNMP MIBs are not
1243 supported and must be converted to their numeric forms.
<br>
1245 "timeout
" specifies the timeout for each OID query. The total amount of
1246 time will depend on the number of OID values found and the time required
1249 "cb
" provides a function to call for every value that is found.
"context
"
1250 is an application-defined pointer that is sent to the callback function
1251 along with the OID and current data. The data passed to the callback is the
1252 same as returned by
<a href=
"#cupsSideChannelSNMPGet"><code>cupsSideChannelSNMPGet
</code></a>.
1254 <code>CUPS_SC_STATUS_NOT_IMPLEMENTED
</code> is returned by backends that do not
1255 support SNMP queries.
<code>CUPS_SC_STATUS_NO_RESPONSE
</code> is returned when
1256 the printer does not respond to the first SNMP query.
1259 <h3 class=
"function"><span class=
"info"> CUPS
1.3/Mac OS X
10.5 </span><a name=
"cupsSideChannelWrite">cupsSideChannelWrite
</a></h3>
1260 <p class=
"description">Write a side-channel message.
</p>
1262 int cupsSideChannelWrite (
<br>
1263 <a href=
"#cups_sc_command_t">cups_sc_command_t
</a> command,
<br>
1264 <a href=
"#cups_sc_status_t">cups_sc_status_t
</a> status,
<br>
1265 const char *data,
<br>
1266 int datalen,
<br>
1267 double timeout
<br>
1269 <h4 class=
"parameters">Parameters
</h4>
1272 <dd class=
"description">Command code
</dd>
1274 <dd class=
"description">Status code
</dd>
1276 <dd class=
"description">Data buffer pointer
</dd>
1278 <dd class=
"description">Number of bytes of data
</dd>
1280 <dd class=
"description">Timeout in seconds
</dd>
1282 <h4 class=
"returnvalue">Return Value
</h4>
1283 <p class=
"description">0 on success, -
1 on error
</p>
1284 <h4 class=
"discussion">Discussion
</h4>
1285 <p class=
"discussion">This function is normally only called by backend programs to send
1286 responses to a filter, driver, or port monitor program.
1289 <h2 class=
"title"><a name=
"TYPES">Data Types
</a></h2>
1290 <h3 class=
"typedef"><a name=
"cups_backend_t">cups_backend_t
</a></h3>
1291 <p class=
"description">Backend exit codes
</p>
1293 typedef enum
<a href=
"#cups_backend_e">cups_backend_e
</a> cups_backend_t;
1295 <h3 class=
"typedef"><a name=
"cups_sc_bidi_t">cups_sc_bidi_t
</a></h3>
1296 <p class=
"description">Bidirectional capabilities
</p>
1298 typedef enum
<a href=
"#cups_sc_bidi_e">cups_sc_bidi_e
</a> cups_sc_bidi_t;
1300 <h3 class=
"typedef"><a name=
"cups_sc_command_t">cups_sc_command_t
</a></h3>
1301 <p class=
"description">Request command codes
</p>
1303 typedef enum
<a href=
"#cups_sc_command_e">cups_sc_command_e
</a> cups_sc_command_t;
1305 <h3 class=
"typedef"><a name=
"cups_sc_state_t">cups_sc_state_t
</a></h3>
1306 <p class=
"description">Printer state bits
</p>
1308 typedef enum
<a href=
"#cups_sc_state_e">cups_sc_state_e
</a> cups_sc_state_t;
1310 <h3 class=
"typedef"><a name=
"cups_sc_status_t">cups_sc_status_t
</a></h3>
1311 <p class=
"description">Response status codes
</p>
1313 typedef enum
<a href=
"#cups_sc_status_e">cups_sc_status_e
</a> cups_sc_status_t;
1315 <h3 class=
"typedef"><a name=
"cups_sc_walk_func_t">cups_sc_walk_func_t
</a></h3>
1316 <p class=
"description">SNMP walk callback
</p>
1318 typedef void (*cups_sc_walk_func_t)(const char *oid, const char *data, int datalen, void *context);
1320 <h2 class=
"title"><a name=
"ENUMERATIONS">Constants
</a></h2>
1321 <h3 class=
"enumeration"><a name=
"cups_backend_e">cups_backend_e
</a></h3>
1322 <p class=
"description">Backend exit codes
</p>
1323 <h4 class=
"constants">Constants
</h4>
1325 <dt>CUPS_BACKEND_AUTH_REQUIRED
</dt>
1326 <dd class=
"description">Job failed, authentication required
</dd>
1327 <dt>CUPS_BACKEND_CANCEL
</dt>
1328 <dd class=
"description">Job failed, cancel job
</dd>
1329 <dt>CUPS_BACKEND_FAILED
</dt>
1330 <dd class=
"description">Job failed, use error-policy
</dd>
1331 <dt>CUPS_BACKEND_HOLD
</dt>
1332 <dd class=
"description">Job failed, hold job
</dd>
1333 <dt>CUPS_BACKEND_OK
</dt>
1334 <dd class=
"description">Job completed successfully
</dd>
1335 <dt>CUPS_BACKEND_STOP
</dt>
1336 <dd class=
"description">Job failed, stop queue
</dd>
1338 <h3 class=
"enumeration"><a name=
"cups_sc_bidi_e">cups_sc_bidi_e
</a></h3>
1339 <p class=
"description">Bidirectional capability values
</p>
1340 <h4 class=
"constants">Constants
</h4>
1342 <dt>CUPS_SC_BIDI_NOT_SUPPORTED
</dt>
1343 <dd class=
"description">Bidirectional I/O is not supported
</dd>
1344 <dt>CUPS_SC_BIDI_SUPPORTED
</dt>
1345 <dd class=
"description">Bidirectional I/O is supported
</dd>
1347 <h3 class=
"enumeration"><a name=
"cups_sc_command_e">cups_sc_command_e
</a></h3>
1348 <p class=
"description">Request command codes
</p>
1349 <h4 class=
"constants">Constants
</h4>
1351 <dt>CUPS_SC_CMD_DRAIN_OUTPUT
</dt>
1352 <dd class=
"description">Drain all pending output
</dd>
1353 <dt>CUPS_SC_CMD_GET_BIDI
</dt>
1354 <dd class=
"description">Return bidirectional capabilities
</dd>
1355 <dt>CUPS_SC_CMD_GET_DEVICE_ID
</dt>
1356 <dd class=
"description">Return the IEEE-
1284 device ID
</dd>
1357 <dt>CUPS_SC_CMD_GET_STATE
</dt>
1358 <dd class=
"description">Return the device state
</dd>
1359 <dt>CUPS_SC_CMD_SNMP_GET
<span class=
"info"> CUPS
1.4/Mac OS X
10.6 </span></dt>
1360 <dd class=
"description">Query an SNMP OID
</dd>
1361 <dt>CUPS_SC_CMD_SNMP_GET_NEXT
<span class=
"info"> CUPS
1.4/Mac OS X
10.6 </span></dt>
1362 <dd class=
"description">Query the next SNMP OID
</dd>
1363 <dt>CUPS_SC_CMD_SOFT_RESET
</dt>
1364 <dd class=
"description">Do a soft reset
</dd>
1366 <h3 class=
"enumeration"><a name=
"cups_sc_state_e">cups_sc_state_e
</a></h3>
1367 <p class=
"description">Printer state bits
</p>
1368 <h4 class=
"constants">Constants
</h4>
1370 <dt>CUPS_SC_STATE_BUSY
</dt>
1371 <dd class=
"description">Device is busy
</dd>
1372 <dt>CUPS_SC_STATE_ERROR
</dt>
1373 <dd class=
"description">Other error condition
</dd>
1374 <dt>CUPS_SC_STATE_MARKER_EMPTY
</dt>
1375 <dd class=
"description">Toner/ink out condition
</dd>
1376 <dt>CUPS_SC_STATE_MARKER_LOW
</dt>
1377 <dd class=
"description">Toner/ink low condition
</dd>
1378 <dt>CUPS_SC_STATE_MEDIA_EMPTY
</dt>
1379 <dd class=
"description">Paper out condition
</dd>
1380 <dt>CUPS_SC_STATE_MEDIA_LOW
</dt>
1381 <dd class=
"description">Paper low condition
</dd>
1382 <dt>CUPS_SC_STATE_OFFLINE
</dt>
1383 <dd class=
"description">Device is offline
</dd>
1384 <dt>CUPS_SC_STATE_ONLINE
</dt>
1385 <dd class=
"description">Device is online
</dd>
1387 <h3 class=
"enumeration"><a name=
"cups_sc_status_e">cups_sc_status_e
</a></h3>
1388 <p class=
"description">Response status codes
</p>
1389 <h4 class=
"constants">Constants
</h4>
1391 <dt>CUPS_SC_STATUS_BAD_MESSAGE
</dt>
1392 <dd class=
"description">The command/response message was invalid
</dd>
1393 <dt>CUPS_SC_STATUS_IO_ERROR
</dt>
1394 <dd class=
"description">An I/O error occurred
</dd>
1395 <dt>CUPS_SC_STATUS_NONE
</dt>
1396 <dd class=
"description">No status
</dd>
1397 <dt>CUPS_SC_STATUS_NOT_IMPLEMENTED
</dt>
1398 <dd class=
"description">Command not implemented
</dd>
1399 <dt>CUPS_SC_STATUS_NO_RESPONSE
</dt>
1400 <dd class=
"description">The device did not respond
</dd>
1401 <dt>CUPS_SC_STATUS_OK
</dt>
1402 <dd class=
"description">Operation succeeded
</dd>
1403 <dt>CUPS_SC_STATUS_TIMEOUT
</dt>
1404 <dd class=
"description">The backend did not respond
</dd>
1405 <dt>CUPS_SC_STATUS_TOO_BIG
</dt>
1406 <dd class=
"description">Response too big
</dd>