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+ </head>
+ <body>
<!--
- "$Id: api-filter.header 8087 2008-10-27 21:37:05Z mike $"
+ Filter and backend programming header for CUPS.
- Filter and backend programming header for the Common UNIX Printing System
- (CUPS).
+ Copyright © 2008-2016 by Apple Inc.
- Copyright 2008 by Apple Inc.
-
- These coded instructions, statements, and computer programs are the
- property of Apple Inc. and are protected by Federal copyright
- law. Distribution and use rights are outlined in the file "LICENSE.txt"
- which should have been included with this file. If this file is
- file is missing or damaged, see the license at "http://www.cups.org/".
+ Licensed under Apache License v2.0. See the file "LICENSE" for more
+ information.
-->
+<h1 class='title'>Filter and Backend Programming</h1>
+
<div class='summary'><table summary='General Information'>
<thead>
<tr>
<th>Headers</th>
<th>cups/backend.h<br>
+ cups/ppd.h<br>
cups/sidechannel.h</th>
</tr>
</thead>
Programming: <a href='api-cups.html' target='_top'>CUPS API</a><br>
Programming: <a href='api-ppd.html' target='_top'>PPD API</a><br>
Programming: <a href='api-raster.html' target='_top'>Raster API</a><br>
- Specifications: <a href='spec-design' target='_top'>CUPS Design Description</a></td>
+ Programming: <a href='postscript-driver.html' target='_top'>Developing PostScript Printer Drivers</a><br>
+ Programming: <a href='raster-driver.html' target='_top'>Developing Raster Printer Drivers</a><br>
+ Specifications: <a href='spec-design.html' target='_top'>CUPS Design Description</a></td>
</tr>
</tbody>
</table></div>
-<h2 class="title">Contents</h2>
-<ul class="contents">
-<ul class="subcontents">
-<li><a href="#OVERVIEW">Overview</a><ul class="subcontents">
-<li><a href="#SECURITY">Security Considerations</a></li>
-<li><a href="#TEMPFILES">Temporary Files</a></li>
-<li><a href="#COPIES">Copy Generation</a></li>
-<li><a href="#EXITCODES">Exit Codes</a></li>
-<li><a href="#ENVIRONMENT">Environment Variables</a></li>
-<li><a href="#MESSAGES">Communicating with the Scheduler</a></li>
-<li><a href="#COMMUNICATING_BACKEND">Communicating with the Backend</a></li>
-<li><a href="#COMMUNICATING_FILTER">Communicating with Filters</a></li>
-<li><a href="#SNMP">Doing SNMP Queries with Network Printers</a></li>
-</ul></li>
-<li><a href="#FUNCTIONS">Functions</a><ul class="code">
-<li><a href="#cupsBackChannelRead" title="Read data from the backchannel.">cupsBackChannelRead</a></li>
-<li><a href="#cupsBackChannelWrite" title="Write data to the backchannel.">cupsBackChannelWrite</a></li>
-<li><a href="#cupsBackendDeviceURI" title="Get the device URI for a backend.">cupsBackendDeviceURI</a></li>
-<li><a href="#cupsBackendReport" title="Write a device line from a backend.">cupsBackendReport</a></li>
-<li><a href="#cupsSideChannelDoRequest" title="Send a side-channel command to a backend and wait for a response.">cupsSideChannelDoRequest</a></li>
-<li><a href="#cupsSideChannelRead" title="Read a side-channel message.">cupsSideChannelRead</a></li>
-<li><a href="#cupsSideChannelSNMPGet" title="Query a SNMP OID's value.">cupsSideChannelSNMPGet</a></li>
-<li><a href="#cupsSideChannelSNMPWalk" title="Query multiple SNMP OID values.">cupsSideChannelSNMPWalk</a></li>
-<li><a href="#cupsSideChannelWrite" title="Write a side-channel message.">cupsSideChannelWrite</a></li>
-</ul></li>
-<li><a href="#TYPES">Data Types</a><ul class="code">
- <li><a href="#cups_backend_t" title="Backend exit codes">cups_backend_t</a></li>
- <li><a href="#cups_sc_bidi_t" title="Bidirectional capabilities">cups_sc_bidi_t</a></li>
- <li><a href="#cups_sc_command_t" title="Request command codes">cups_sc_command_t</a></li>
- <li><a href="#cups_sc_state_t" title="Printer state bits">cups_sc_state_t</a></li>
- <li><a href="#cups_sc_status_t" title="Response status codes">cups_sc_status_t</a></li>
- <li><a href="#cups_sc_walk_func_t" title="SNMP walk callback">cups_sc_walk_func_t</a></li>
-</ul></li>
-<li><a href="#ENUMERATIONS">Constants</a><ul class="code">
- <li><a href="#cups_backend_e" title="Backend exit codes">cups_backend_e</a></li>
- <li><a href="#cups_sc_bidi_e" title="Bidirectional capability values">cups_sc_bidi_e</a></li>
- <li><a href="#cups_sc_command_e" title="Request command codes">cups_sc_command_e</a></li>
- <li><a href="#cups_sc_state_e" title="Printer state bits">cups_sc_state_e</a></li>
- <li><a href="#cups_sc_status_e" title="Response status codes">cups_sc_status_e</a></li>
-</ul></li>
+ <div class="contents">
+ <h2 class="title">Contents</h2>
+ <ul class="contents">
+ <li><a href="#OVERVIEW">Overview</a><ul class="subcontents">
+ <li><a href="#SECURITY">Security Considerations</a></li>
+ <li><a href="#SIGNALS">Canceled Jobs and Signal Handling</a></li>
+ <li><a href="#PERMISSIONS">File Permissions</a></li>
+ <li><a href="#TEMPFILES">Temporary Files</a></li>
+ <li><a href="#COPIES">Copy Generation</a></li>
+ <li><a href="#EXITCODES">Exit Codes</a></li>
+ <li><a href="#ENVIRONMENT">Environment Variables</a></li>
+ <li><a href="#MESSAGES">Communicating with the Scheduler</a></li>
+ <li><a href="#COMMUNICATING_BACKEND">Communicating with the Backend</a></li>
+ <li><a href="#COMMUNICATING_FILTER">Communicating with Filters</a></li>
+ <li><a href="#SNMP">Doing SNMP Queries with Network Printers</a></li>
+ </ul></li>
+ <li><a href="#SANDBOXING">Sandboxing on macOS</a></li>
+ <li><a href="#FUNCTIONS">Functions</a><ul class="subcontents">
+ <li><a href="#cupsBackChannelRead">cupsBackChannelRead</a></li>
+ <li><a href="#cupsBackChannelWrite">cupsBackChannelWrite</a></li>
+ <li><a href="#cupsBackendDeviceURI">cupsBackendDeviceURI</a></li>
+ <li><a href="#cupsBackendReport">cupsBackendReport</a></li>
+ <li><a href="#cupsSideChannelDoRequest">cupsSideChannelDoRequest</a></li>
+ <li><a href="#cupsSideChannelRead">cupsSideChannelRead</a></li>
+ <li><a href="#cupsSideChannelSNMPGet">cupsSideChannelSNMPGet</a></li>
+ <li><a href="#cupsSideChannelSNMPWalk">cupsSideChannelSNMPWalk</a></li>
+ <li><a href="#cupsSideChannelWrite">cupsSideChannelWrite</a></li>
+ </ul></li>
+ <li><a href="#TYPES">Data Types</a><ul class="subcontents">
+ <li><a href="#cups_backend_t">cups_backend_t</a></li>
+ <li><a href="#cups_sc_bidi_t">cups_sc_bidi_t</a></li>
+ <li><a href="#cups_sc_command_t">cups_sc_command_t</a></li>
+ <li><a href="#cups_sc_connected_t">cups_sc_connected_t</a></li>
+ <li><a href="#cups_sc_state_t">cups_sc_state_t</a></li>
+ <li><a href="#cups_sc_status_t">cups_sc_status_t</a></li>
+ <li><a href="#cups_sc_walk_func_t">cups_sc_walk_func_t</a></li>
+ </ul></li>
+ <li><a href="#ENUMERATIONS">Enumerations</a><ul class="subcontents">
+ <li><a href="#cups_backend_e">cups_backend_e</a></li>
+ <li><a href="#cups_sc_bidi_e">cups_sc_bidi_e</a></li>
+ <li><a href="#cups_sc_command_e">cups_sc_command_e</a></li>
+ <li><a href="#cups_sc_connected_e">cups_sc_connected_e</a></li>
+ <li><a href="#cups_sc_state_e">cups_sc_state_e</a></li>
+ <li><a href="#cups_sc_status_e">cups_sc_status_e</a></li>
+ </ul></li>
+ </ul>
+ </div>
+ <div class="body">
<!--
- "$Id: api-filter.shtml 7962 2008-09-18 17:31:33Z mike $"
+ Filter and backend programming introduction for CUPS.
- Filter and backend programming introduction for the Common UNIX Printing
- System (CUPS).
+ Copyright © 2007-2016 by Apple Inc.
+ Copyright © 1997-2006 by Easy Software Products, all rights reserved.
- Copyright 2007-2008 by Apple Inc.
- Copyright 1997-2006 by Easy Software Products, all rights reserved.
-
- These coded instructions, statements, and computer programs are the
- property of Apple Inc. and are protected by Federal copyright
- law. Distribution and use rights are outlined in the file "LICENSE.txt"
- which should have been included with this file. If this file is
- file is missing or damaged, see the license at "http://www.cups.org/".
+ Licensed under Apache License v2.0. See the file "LICENSE" for more
+ information.
-->
<h2 class='title'><a name="OVERVIEW">Overview</a></h2>
output. The backend is the last filter in the chain and writes to the
device.</p>
+<p>Filters are always run as a non-privileged user, typically "lp", with no
+connection to the user's desktop. Backends are run either as a non-privileged
+user or as root if the file permissions do not allow user or group execution.
+The <a href="#PERMISSIONS">file permissions</a> section talks about this in
+more detail.</p>
+
<h3><a name="SECURITY">Security Considerations</a></h3>
<p>It is always important to use security programming practices. Filters and
-most backends are run as a non-priviledged user, so the major security
+most backends are run as a non-privileged user, so the major security
consideration is resource utilization - filters should not depend on unlimited
amounts of CPU, memory, or disk space, and should protect against conditions
that could lead to excess usage of any resource like infinite loops and
directory to write to.</p>
<p>In addition, some operating systems provide additional security mechanisms
-that further limit file system access, even for backends running as root. On
-Mac OS X, for example, no backend may write to a user's home directory.</p>
+that further limit file system access, even for backends running as root. On
+macOS, for example, no backend may write to a user's home directory. See the <a href="#SANDBOXING">Sandboxing on macOS</a> section for more information.</p>
</blockquote>
+<h3><a name="SIGNALS">Canceled Jobs and Signal Handling</a></h3>
+
+<p>The scheduler sends <code>SIGTERM</code> when a printing job is canceled or
+held. Filters, backends, and port monitors <em>must</em> catch
+<code>SIGTERM</code> and perform any cleanup necessary to produce a valid output
+file or return the printer to a known good state. The recommended behavior is to
+end the output on the current page, preferably on the current line or object
+being printed.</p>
+
+<p>Filters and backends may also receive <code>SIGPIPE</code> when an upstream or downstream filter/backend exits with a non-zero status. Developers should generally ignore <code>SIGPIPE</code> at the beginning of <code>main()</code> with the following function call:</p>
+
+<pre class="example">
+#include <signal.h>
+
+...
+
+int
+main(int argc, char *argv[])
+{
+ signal(SIGPIPE, SIG_IGN);
+
+ ...
+}
+</pre>
+
+<h3><a name="PERMISSIONS">File Permissions</a></h3>
+
+<p>For security reasons, CUPS will only run filters and backends that are owned
+by root and do not have world or group write permissions. The recommended
+permissions for filters and backends are 0555 - read and execute but no write.
+Backends that must run as root should use permissions of 0500 - read and execute
+by root, no access for other users. Write permissions can be enabled for the
+root user only.</p>
+
+<p>To avoid a warning message, the directory containing your filter(s) must also
+be owned by root and have world and group write disabled - permissions of 0755
+or 0555 are strongly encouraged.</p>
+
<h3><a name="TEMPFILES">Temporary Files</a></h3>
<p>Temporary files should be created in the directory specified by the
<dl class="code">
- <dt>APPLE_LANGUAGES</dt>
+ <dt>APPLE_LANGUAGE</dt>
<dd>The Apple language identifier associated with the job
- (Mac OS X only).</dd>
+ (macOS only).</dd>
<dt>CHARSET</dt>
<dd>The job character set, typically "utf-8".</dd>
<dt>ATTR: attribute=value [attribute=value]</dt>
<dd>Sets the named printer or job attribute(s). Typically this is used
- to set the <code>marker-colors</code>, <code>marker-levels</code>,
+ to set the <code>marker-colors</code>, <code>marker-high-levels</code>,
+ <code>marker-levels</code>, <code>marker-low-levels</code>,
<code>marker-message</code>, <code>marker-names</code>,
<code>marker-types</code>, <code>printer-alert</code>, and
<code>printer-alert-description</code> printer attributes. Standard
<code>marker-types</code> values are listed in <a href='#TABLE1'>Table
- 1</a>.</dd>
+ 1</a>. String values need special handling - see <a href="#ATTR_STRINGS">Reporting Attribute String Values</a> below.</dd>
<dt>CRIT: message</dt>
<dd>Sets the printer-state-message attribute and adds the specified
this is used to update installable options or default media settings
based on the printer configuration.</dd>
- <dt>STATE: printer-state-reason [printer-state-reason ...]</dt>
<dt>STATE: + printer-state-reason [printer-state-reason ...]</dt>
<dt>STATE: - printer-state-reason [printer-state-reason ...]</dt>
- <dd>Sets, adds, or removes printer-state-reason keywords to the
- current queue. Typically this is used to indicate persistent media,
- ink, toner, and configuration conditions or errors on a printer.
- <a href='#TABLE2'>Table 2</a> lists the standard state keywords -
- use vendor-prefixed ("com.acme.foo") keywords for custom states.</dd>
+ <dd>Sets or clears printer-state-reason keywords for the current queue.
+ Typically this is used to indicate persistent media, ink, toner, and
+ configuration conditions or errors on a printer.
+ <a href='#TABLE2'>Table 2</a> lists some of the standard "printer-state-reasons" keywords from the <a href="http://www.iana.org/assignments/ipp-registrations/ipp-registrations.xhtml#ipp-registrations-4">IANA IPP Registry</a> -
+ use vendor-prefixed ("com.example.foo") keywords for custom states. See
+ <a href="#MANAGING_STATE">Managing Printer State in a Filter</a> for more
+ information.
<dt>WARNING: message</dt>
<dd>Sets the printer-state-message attribute and adds the specified
<p>Messages without one of these prefixes are treated as if they began with
the "DEBUG:" prefix string.</p>
-
<div class='table'><table width='80%' summary='Table 1: Standard marker-types Values'>
<caption>Table 1: <a name='TABLE1'>Standard marker-types Values</a></caption>
<thead>
<td>Fuser unit</td>
</tr>
<tr>
- <td>fuserCleaningPad</td>
+ <td>fuser-cleaning-pad</td>
<td>Fuser cleaning pad</td>
</tr>
<tr>
- <td>fuserOil</td>
+ <td>fuser-oil</td>
<td>Fuser oil</td>
</tr>
<tr>
<td>Photo conductor</td>
</tr>
<tr>
- <td>solidWax</td>
+ <td>solid-wax</td>
<td>Wax supply</td>
</tr>
<tr>
<td>Toner supply</td>
</tr>
<tr>
- <td>transferUnit</td>
+ <td>transfer-unit</td>
<td>Transfer unit</td>
</tr>
<tr>
- <td>wasteInk</td>
+ <td>waste-ink</td>
<td>Waste ink tank</td>
</tr>
<tr>
- <td>wasteToner</td>
+ <td>waste-toner</td>
<td>Waste toner tank</td>
</tr>
<tr>
- <td>wasteWax</td>
+ <td>waste-wax</td>
<td>Waste wax tank</td>
</tr>
</tbody>
<tbody>
<tr>
<td>connecting-to-device</td>
- <td>Connecting to printer but not printing yet</td>
+ <td>Connecting to printer but not printing yet.</td>
</tr>
<tr>
<td>cover-open</td>
- <td>A cover is open on the printer</td>
+ <td>The printer's cover is open.</td>
</tr>
<tr>
<td>input-tray-missing</td>
- <td>An input tray is missing from the printer</td>
+ <td>The paper tray is missing.</td>
</tr>
<tr>
<td>marker-supply-empty</td>
- <td>Out of ink</td>
+ <td>The printer is out of ink.</td>
</tr>
<tr>
<td>marker-supply-low</td>
- <td>Low on ink</td>
+ <td>The printer is almost out of ink.</td>
</tr>
<tr>
<td>marker-waste-almost-full</td>
- <td>Waste tank almost full</td>
+ <td>The printer's waste bin is almost full.</td>
</tr>
<tr>
<td>marker-waste-full</td>
- <td>Waste tank full</td>
+ <td>The printer's waste bin is full.</td>
</tr>
<tr>
<td>media-empty</td>
- <td>Out of media</td>
+ <td>The paper tray (any paper tray) is empty.</td>
</tr>
<tr>
<td>media-jam</td>
- <td>Media is jammed in the printer</td>
+ <td>There is a paper jam.</td>
</tr>
<tr>
<td>media-low</td>
- <td>Low on media</td>
+ <td>The paper tray (any paper tray) is almost empty.</td>
+</tr>
+<tr>
+ <td>media-needed</td>
+ <td>The paper tray needs to be filled (for a job that is printing).</td>
</tr>
<tr>
<td>paused</td>
- <td>Stop the printer</td>
+ <td>Stop the printer.</td>
</tr>
<tr>
<td>timed-out</td>
- <td>Unable to connect to printer</td>
+ <td>Unable to connect to printer.</td>
</tr>
<tr>
<td>toner-empty</td>
- <td>Out of toner</td>
+ <td>The printer is out of toner.</td>
</tr>
<tr>
<td>toner-low</td>
- <td>Low on toner</td>
+ <td>The printer is low on toner.</td>
+</tr>
+</tbody>
+</table></div>
+
+
+<h4><a name="ATTR_STRINGS">Reporting Attribute String Values</a></h4>
+
+<p>When reporting string values using "ATTR:" messages, a filter or backend must take special care to appropriately quote those values. The scheduler uses the CUPS option parsing code for attributes, so the general syntax is:</p>
+
+<pre class="example">
+name=simple
+name=simple,simple,...
+name='complex value'
+name="complex value"
+name='"complex value"','"complex value"',...
+</pre>
+
+<p>Simple values are strings that do not contain spaces, quotes, backslashes, or the comma and can be placed verbatim in the "ATTR:" message, for example:</p>
+
+<pre class="example">
+int levels[4] = { 40, 50, 60, 70 }; /* CMYK */
+
+fputs("ATTR: marker-colors=#00FFFF,#FF00FF,#FFFF00,#000000\n", stderr);
+fputs("ATTR: marker-high-levels=100,100,100,100\n", stderr);
+fprintf(stderr, "ATTR: marker-levels=%d,%d,%d,%d\n", levels[0], levels[1],
+ levels[2], levels[3], levels[4]);
+fputs("ATTR: marker-low-levels=5,5,5,5\n", stderr);
+fputs("ATTR: marker-types=toner,toner,toner,toner\n", stderr);
+</pre>
+
+<p>Complex values that contains spaces, quotes, backslashes, or the comma must be quoted. For a single value a single set of quotes is sufficient:</p>
+
+<pre class="example">
+fputs("ATTR: marker-message='Levels shown are approximate.'\n", stderr);
+</pre>
+
+<p>When multiple values are reported, each value must be enclosed by a set of single and double quotes:</p>
+
+<pre class="example">
+fputs("ATTR: marker-names='\"Cyan Toner\"','\"Magenta Toner\"',"
+ "'\"Yellow Toner\"','\"Black Toner\"'\n", stderr);
+</pre>
+
+<p>The IPP backend includes a <var>quote_string</var> function that may be used to properly quote a complex value in an "ATTR:" message:</p>
+
+<pre class="example">
+static const char * /* O - Quoted string */
+quote_string(const char *s, /* I - String */
+ char *q, /* I - Quoted string buffer */
+ size_t qsize) /* I - Size of quoted string buffer */
+{
+ char *qptr, /* Pointer into string buffer */
+ *qend; /* End of string buffer */
+
+
+ qptr = q;
+ qend = q + qsize - 5;
+
+ if (qend < q)
+ {
+ *q = '\0';
+ return (q);
+ }
+
+ *qptr++ = '\'';
+ *qptr++ = '\"';
+
+ while (*s && qptr < qend)
+ {
+ if (*s == '\\' || *s == '\"' || *s == '\'')
+ {
+ if (qptr < (qend - 4))
+ {
+ *qptr++ = '\\';
+ *qptr++ = '\\';
+ *qptr++ = '\\';
+ }
+ else
+ break;
+ }
+
+ *qptr++ = *s++;
+ }
+
+ *qptr++ = '\"';
+ *qptr++ = '\'';
+ *qptr = '\0';
+
+ return (q);
+}
+</pre>
+
+
+<h4><a name="MANAGING_STATE">Managing Printer State in a Filter</a></h4>
+
+<p>Filters are responsible for managing the state keywords they set using
+"STATE:" messages. Typically you will update <em>all</em> of the keywords that
+are used by the filter at startup, for example:</p>
+
+<pre class="example">
+if (foo_condition != 0)
+ fputs("STATE: +com.example.foo\n", stderr);
+else
+ fputs("STATE: -com.example.foo\n", stderr);
+
+if (bar_condition != 0)
+ fputs("STATE: +com.example.bar\n", stderr);
+else
+ fputs("STATE: -com.example.bar\n", stderr);
+</pre>
+
+<p>Then as conditions change, your filter sends "STATE: +keyword" or "STATE:
+-keyword" messages as necessary to set or clear the corresponding keyword,
+respectively.</p>
+
+<p>State keywords are often used to notify the user of issues that span across
+jobs, for example "media-empty-warning" that indicates one or more paper trays
+are empty. These keywords should not be cleared unless the corresponding issue
+no longer exists.</p>
+
+<p>Filters should clear job-related keywords on startup and exit so that they
+do not remain set between jobs. For example, "connecting-to-device" is a job
+sub-state and not an issue that applies when a job is not printing.</p>
+
+<blockquote><b>Note:</b>
+
+<p>"STATE:" messages often provide visible alerts to the user. For example,
+on macOS setting a printer-state-reason value with an "-error" or
+"-warning" suffix will cause the printer's dock item to bounce if the
+corresponding reason is localized with a cupsIPPReason keyword in the
+printer's PPD file.</p>
+
+<p>When providing a vendor-prefixed keyword, <em>always</em> provide the
+corresponding standard keyword (if any) to allow clients to respond to the
+condition correctly. For example, if you provide a vendor-prefixed keyword
+for a low cyan ink condition ("com.example.cyan-ink-low") you must also set the
+"marker-supply-low-warning" keyword. In such cases you should also refrain
+from localizing the vendor-prefixed keyword in the PPD file - otherwise both
+the generic and vendor-specific keyword will be shown in the user
+interface.</p>
+
+</blockquote>
+
+<h4><a name="REPORTING_SUPPLIES">Reporting Supply Levels</a></h4>
+
+<p>CUPS tracks several "marker-*" attributes for ink/toner supply level
+reporting. These attributes allow applications to display the current supply
+levels for a printer without printer-specific software. <a href="#TABLE3">Table 3</a> lists the marker attributes and what they represent.</p>
+
+<p>Filters set marker attributes by sending "ATTR:" messages to stderr. For
+example, a filter supporting an inkjet printer with black and tri-color ink
+cartridges would use the following to initialize the supply attributes:</p>
+
+<pre class="example">
+fputs("ATTR: marker-colors=#000000,#00FFFF#FF00FF#FFFF00\n", stderr);
+fputs("ATTR: marker-low-levels=5,10\n", stderr);
+fputs("ATTR: marker-names=Black,Tri-Color\n", stderr);
+fputs("ATTR: marker-types=ink,ink\n", stderr);
+</pre>
+
+<p>Then periodically the filter queries the printer for its current supply
+levels and updates them with a separate "ATTR:" message:</p>
+
+<pre class="example">
+int black_level, tri_level;
+...
+fprintf(stderr, "ATTR: marker-levels=%d,%d\n", black_level, tri_level);
+</pre>
+
+<div class='table'><table width='80%' summary='Table 3: Supply Level Attributes'>
+<caption>Table 3: <a name='TABLE3'>Supply Level Attributes</a></caption>
+<thead>
+<tr>
+ <th>Attribute</th>
+ <th>Description</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+ <td>marker-colors</td>
+ <td>A list of comma-separated colors; each color is either "none" or one or
+ more hex-encoded sRGB colors of the form "#RRGGBB".</td>
+</tr>
+<tr>
+ <td>marker-high-levels</td>
+ <td>A list of comma-separated "almost full" level values from 0 to 100; a
+ value of 100 should be used for supplies that are consumed/emptied like ink
+ cartridges.</td>
+</tr>
+<tr>
+ <td>marker-levels</td>
+ <td>A list of comma-separated level values for each supply. A value of -1
+ indicates the level is unavailable, -2 indicates unknown, and -3 indicates
+ the level is unknown but has not yet reached capacity. Values from 0 to 100
+ indicate the corresponding percentage.</td>
+</tr>
+<tr>
+ <td>marker-low-levels</td>
+ <td>A list of comma-separated "almost empty" level values from 0 to 100; a
+ value of 0 should be used for supplies that are filled like waste ink
+ tanks.</td>
+</tr>
+<tr>
+ <td>marker-message</td>
+ <td>A human-readable supply status message for the user like "12 pages of
+ ink remaining."</td>
+</tr>
+<tr>
+ <td>marker-names</td>
+ <td>A list of comma-separated supply names like "Cyan Ink", "Fuser",
+ etc.</td>
+</tr>
+<tr>
+ <td>marker-types</td>
+ <td>A list of comma-separated supply types; the types are listed in
+ <a href="#TABLE1">Table 1</a>.</td>
</tr>
</tbody>
</table></div>
<p>Filters can communicate with the backend via the
<a href="#cupsBackChannelRead"><code>cupsBackChannelRead</code></a> and
<a href="#cupsSideChannelDoRequest"><code>cupsSideChannelDoRequest</code></a>
-functions. The
+functions. The
<a href="#cupsBackChannelRead"><code>cupsBackChannelRead</code></a> function
reads data that has been sent back from the device and is typically used to
obtain status and configuration information. For example, the following code
status = <a href="#cupsSideChannelDoRequest">cupsSideChannelDoRequest</a>(CUPS_SC_CMD_GET_DEVICE_ID, data, &datalen, 1.0);
/* Use the returned value if OK was returned and the length is non-zero */
-if (status == CUPS_SC_STATUS_OK && datalen > 0)
+if (status == CUPS_SC_STATUS_OK && datalen > 0)
data[datalen] = '\0';
else
data[0] = '\0';
</pre>
+<h4><a name="DRAIN_OUTPUT">Forcing All Output to a Printer</a></h4>
+
+<p>The
+<a href="#cupsSideChannelDoRequest"><code>cupsSideChannelDoRequest</code></a>
+function allows you to tell the backend to send all pending data to the printer.
+This is most often needed when sending query commands to the printer. For example:</p>
+
+<pre class="example">
+#include <cups/cups.h>
+#include <cups/sidechannel.h>
+
+char data[1024];
+int datalen = sizeof(data);
+<a href="#cups_sc_status_t">cups_sc_status_t</a> status;
+
+/* Flush pending output to stdout */
+fflush(stdout);
+
+/* Drain output to backend, waiting for up to 30 seconds */
+status = <a href="#cupsSideChannelDoRequest">cupsSideChannelDoRequest</a>(CUPS_SC_CMD_DRAIN_OUTPUT, data, &datalen, 30.0);
+
+/* Read the response if the output was sent */
+if (status == CUPS_SC_STATUS_OK)
+{
+ ssize_t bytes;
+
+ /* Wait up to 10.0 seconds for back-channel data */
+ bytes = cupsBackChannelRead(data, sizeof(data), 10.0);
+ /* do something with the data from the printer */
+}
+</pre>
+
<h3><a name="COMMUNICATING_FILTER">Communicating with Filters</a></h3>
<p>Backends communicate with filters using the reciprocal functions
<a href="#cupsSideChannelSNMPWalk">cupsSNMPSideChannelWalk</a>(".1.3.6.1.2.1.43", 5.0, my_callback, my_data);
</pre>
-<h2 class="title"><a name="FUNCTIONS">Functions</a></h2>
-<h3 class="function"><span class="info"> CUPS 1.2/Mac OS X 10.5 </span><a name="cupsBackChannelRead">cupsBackChannelRead</a></h3>
-<p class="description">Read data from the backchannel.</p>
+
+<h2><a name="SANDBOXING">Sandboxing on macOS</a></h2>
+
+<p>Starting with macOS 10.6, filters and backends are run inside a security "sandbox" which further limits (beyond the normal UNIX user/group permissions) what a filter or backend can do. This helps to both secure the printing system from malicious software and enforce the functional separation of components in the CUPS filter chain. What follows is a list of actions that are explicitly allowed for all filters and backends:</p>
+
+<ol>
+
+ <li>Reading of files: pursuant to normal UNIX file permissions, filters and backends can read files for the current job from the <var>/private/var/spool/cups</var> directory and other files on mounted filesystems <em>except</em> for user home directories under <var>/Users</var>.</li>
+
+ <li>Writing of files: pursuant to normal UNIX file permissions, filters and backends can read/write files to the cache directory specified by the <code>CUPS_CACHEDIR</code> environment variable, to the state directory specified by the <code>CUPS_STATEDIR</code> environment variable, to the temporary directory specified by the <code>TMPDIR</code> environment variable, and under the <var>/private/var/db</var>, <var>/private/var/folders</var>, <var>/private/var/lib</var>, <var>/private/var/mysql</var>, <var>/private/var/run</var>, <var>/private/var/spool</var> (except <var>/private/var/spool/cups</var>), <var>/Library/Application Support</var>, <var>/Library/Caches</var>, <var>/Library/Logs</var>, <var>/Library/Preferences</var>, <var>/Library/WebServer</var>, and <var>/Users/Shared</var> directories.</li>
+
+ <li>Execution of programs: pursuant to normal UNIX file permissions, filters and backends can execute any program not located under the <var>/Users</var> directory. Child processes inherit the sandbox and are subject to the same restrictions as the parent.</li>
+
+ <li>Bluetooth and USB: backends can access Bluetooth and USB printers through IOKit. <em>Filters cannot access Bluetooth and USB printers directly.</em></li>
+
+ <li>Network: filters and backends can access UNIX domain sockets under the <var>/private/tmp</var>, <var>/private/var/run</var>, and <var>/private/var/tmp</var> directories. Backends can also create IPv4 and IPv6 TCP (outgoing) and UDP (incoming and outgoing) socket, and bind to local source ports. <em>Filters cannot directly create IPv4 and IPv6 TCP or UDP sockets.</em></li>
+
+ <li>Notifications: filters and backends can send notifications via the Darwin <code>notify_post()</code> API.</li>
+
+</ol>
+
+<blockquote><b>Note:</b> The sandbox profile used in CUPS 2.0 still allows some actions that are not listed above - these privileges will be removed over time until the profile matches the list above.</blockquote>
+ <h2 class="title"><a id="FUNCTIONS">Functions</a></h2>
+<h3 class="function"><span class="info"> CUPS 1.2/macOS 10.5 </span><a id="cupsBackChannelRead">cupsBackChannelRead</a></h3>
+ <p class="description">Read data from the backchannel.</p>
<p class="code">
-ssize_t cupsBackChannelRead (<br>
- char *buffer,<br>
- size_t bytes,<br>
- double timeout<br>
-);</p>
+ssize_t cupsBackChannelRead(char *buffer, size_t bytes, double timeout);</p>
<h4 class="parameters">Parameters</h4>
-<dl>
-<dt>buffer</dt>
-<dd class="description">Buffer to read into</dd>
-<dt>bytes</dt>
-<dd class="description">Bytes to read</dd>
-<dt>timeout</dt>
-<dd class="description">Timeout in seconds, typically 0.0 to poll</dd>
-</dl>
+<table class="list"><tbody>
+<tr><th>buffer</th>
+ <td class="description">Buffer to read into</td></tr>
+<tr><th>bytes</th>
+ <td class="description">Bytes to read</td></tr>
+<tr><th>timeout</th>
+ <td class="description">Timeout in seconds, typically 0.0 to poll</td></tr>
+</tbody></table>
<h4 class="returnvalue">Return Value</h4>
-<p class="description">Bytes read or -1 on error</p>
+
<p class="description">Bytes read or -1 on error</p>
<h4 class="discussion">Discussion</h4>
-<p class="discussion">Reads up to "bytes" bytes from the backchannel/backend. The "timeout"
+
<p class="discussion">Reads up to "bytes" bytes from the backchannel/backend. The "timeout"
parameter controls how many seconds to wait for the data - use 0.0 to
return immediately if there is no data, -1.0 to wait for data indefinitely.
</p>
-<h3 class="function"><span class="info"> CUPS 1.2/Mac OS X 10.5 </span><a name="cupsBackChannelWrite">cupsBackChannelWrite</a></h3>
-<p class="description">Write data to the backchannel.</p>
+<h3 class="function"><span class="info"> CUPS 1.2/macOS 10.5 </span><a id="cupsBackChannelWrite">cupsBackChannelWrite</a></h3>
+
<p class="description">Write data to the backchannel.</p>
<p class="code">
-ssize_t cupsBackChannelWrite (<br>
- const char *buffer,<br>
- size_t bytes,<br>
- double timeout<br>
-);</p>
+ssize_t cupsBackChannelWrite(const char *buffer, size_t bytes, double timeout);</p>
<h4 class="parameters">Parameters</h4>
-<dl>
-<dt>buffer</dt>
-<dd class="description">Buffer to write</dd>
-<dt>bytes</dt>
-<dd class="description">Bytes to write</dd>
-<dt>timeout</dt>
-<dd class="description">Timeout in seconds, typically 1.0</dd>
-</dl>
+<table class="list"><tbody>
+<tr><th>buffer</th>
+ <td class="description">Buffer to write</td></tr>
+<tr><th>bytes</th>
+ <td class="description">Bytes to write</td></tr>
+<tr><th>timeout</th>
+ <td class="description">Timeout in seconds, typically 1.0</td></tr>
+</tbody></table>
<h4 class="returnvalue">Return Value</h4>
-<p class="description">Bytes written or -1 on error</p>
+
<p class="description">Bytes written or -1 on error</p>
<h4 class="discussion">Discussion</h4>
-<p class="discussion">Writes "bytes" bytes to the backchannel/filter. The "timeout" parameter
+
<p class="discussion">Writes "bytes" bytes to the backchannel/filter. The "timeout" parameter
controls how many seconds to wait for the data to be written - use
0.0 to return immediately if the data cannot be written, -1.0 to wait
indefinitely.
</p>
-<h3 class="function"><span class="info"> CUPS 1.2/Mac OS X 10.5 </span><a name="cupsBackendDeviceURI">cupsBackendDeviceURI</a></h3>
-<p class="description">Get the device URI for a backend.</p>
+<h3 class="function"><span class="info"> CUPS 1.2/macOS 10.5 </span><a id="cupsBackendDeviceURI">cupsBackendDeviceURI</a></h3>
+
<p class="description">Get the device URI for a backend.</p>
<p class="code">
-const char *cupsBackendDeviceURI (<br>
- char **argv<br>
-);</p>
+const char *cupsBackendDeviceURI(char **argv);</p>
<h4 class="parameters">Parameters</h4>
-<dl>
-<dt>argv</dt>
-<dd class="description">Command-line arguments</dd>
-</dl>
+<table class="list"><tbody>
+<tr><th>argv</th>
+ <td class="description">Command-line arguments</td></tr>
+</tbody></table>
<h4 class="returnvalue">Return Value</h4>
-<p class="description">Device URI or <code>NULL</code></p>
+
<p class="description">Device URI or <code>NULL</code></p>
<h4 class="discussion">Discussion</h4>
-<p class="discussion">The "argv" argument is the argv argument passed to main(). This
+
<p class="discussion">The "argv" argument is the argv argument passed to main(). This
function returns the device URI passed in the DEVICE_URI environment
variable or the device URI passed in argv[0], whichever is found
first.
</p>
-<h3 class="function"><span class="info"> CUPS 1.4 </span><a name="cupsBackendReport">cupsBackendReport</a></h3>
-<p class="description">Write a device line from a backend.</p>
+<h3 class="function"><span class="info"> CUPS 1.4/macOS 10.6 </span><a id="cupsBackendReport">cupsBackendReport</a></h3>
+
<p class="description">Write a device line from a backend.</p>
<p class="code">
-void cupsBackendReport (<br>
- const char *device_scheme,<br>
- const char *device_uri,<br>
- const char *device_make_and_model,<br>
- const char *device_info,<br>
- const char *device_id,<br>
- const char *device_location<br>
-);</p>
+void cupsBackendReport(const char *device_scheme, const char *device_uri, const char *device_make_and_model, const char *device_info, const char *device_id, const char *device_location);</p>
<h4 class="parameters">Parameters</h4>
-<dl>
-<dt>device_scheme</dt>
-<dd class="description">device-scheme string</dd>
-<dt>device_uri</dt>
-<dd class="description">device-uri string</dd>
-<dt>device_make_and_model</dt>
-<dd class="description">device-make-and-model string or <code>NULL</code></dd>
-<dt>device_info</dt>
-<dd class="description">device-info string or <code>NULL</code></dd>
-<dt>device_id</dt>
-<dd class="description">device-id string or <code>NULL</code></dd>
-<dt>device_location</dt>
-<dd class="description">device-location string or <code>NULL</code></dd>
-</dl>
+<table class="list"><tbody>
+<tr><th>device_scheme</th>
+ <td class="description">device-scheme string</td></tr>
+<tr><th>device_uri</th>
+ <td class="description">device-uri string</td></tr>
+<tr><th>device_make_and_model</th>
+ <td class="description">device-make-and-model string or <code>NULL</code></td></tr>
+<tr><th>device_info</th>
+ <td class="description">device-info string or <code>NULL</code></td></tr>
+<tr><th>device_id</th>
+ <td class="description">device-id string or <code>NULL</code></td></tr>
+<tr><th>device_location</th>
+ <td class="description">device-location string or <code>NULL</code></td></tr>
+</tbody></table>
<h4 class="discussion">Discussion</h4>
-<p class="discussion">This function writes a single device line to stdout for a backend.
+
<p class="discussion">This function writes a single device line to stdout for a backend.
It handles quoting of special characters in the device-make-and-model,
device-info, device-id, and device-location strings.
</p>
-<h3 class="function"><span class="info"> CUPS 1.3/Mac OS X 10.5 </span><a name="cupsSideChannelDoRequest">cupsSideChannelDoRequest</a></h3>
-<p class="description">Send a side-channel command to a backend and wait for a response.</p>
+<h3 class="function"><span class="info"> CUPS 1.3/macOS 10.5 </span><a id="cupsSideChannelDoRequest">cupsSideChannelDoRequest</a></h3>
+
<p class="description">Send a side-channel command to a backend and wait for a response.</p>
<p class="code">
-<a href="#cups_sc_status_t">cups_sc_status_t</a> cupsSideChannelDoRequest (<br>
- <a href="#cups_sc_command_t">cups_sc_command_t</a> command,<br>
- char *data,<br>
- int *datalen,<br>
- double timeout<br>
-);</p>
+<a href="#cups_sc_status_t">cups_sc_status_t</a> cupsSideChannelDoRequest(<a href="#cups_sc_command_t">cups_sc_command_t</a> command, char *data, int *datalen, double timeout);</p>
<h4 class="parameters">Parameters</h4>
-<dl>
-<dt>command</dt>
-<dd class="description">Command to send</dd>
-<dt>data</dt>
-<dd class="description">Response data buffer pointer</dd>
-<dt>datalen</dt>
-<dd class="description">Size of data buffer on entry, number of bytes in buffer on return</dd>
-<dt>timeout</dt>
-<dd class="description">Timeout in seconds</dd>
-</dl>
+<table class="list"><tbody>
+<tr><th>command</th>
+ <td class="description">Command to send</td></tr>
+<tr><th>data</th>
+ <td class="description">Response data buffer pointer</td></tr>
+<tr><th>datalen</th>
+ <td class="description">Size of data buffer on entry, number of bytes in buffer on return</td></tr>
+<tr><th>timeout</th>
+ <td class="description">Timeout in seconds</td></tr>
+</tbody></table>
<h4 class="returnvalue">Return Value</h4>
-<p class="description">Status of command</p>
+
<p class="description">Status of command</p>
<h4 class="discussion">Discussion</h4>
-<p class="discussion">This function is normally only called by filters, drivers, or port
+
<p class="discussion">This function is normally only called by filters, drivers, or port
monitors in order to communicate with the backend used by the current
printer. Programs must be prepared to handle timeout or "not
implemented" status codes, which indicate that the backend or device
update the value to contain the number of data bytes in the buffer.
</p>
-<h3 class="function"><span class="info"> CUPS 1.3/Mac OS X 10.5 </span><a name="cupsSideChannelRead">cupsSideChannelRead</a></h3>
-<p class="description">Read a side-channel message.</p>
+<h3 class="function"><span class="info"> CUPS 1.3/macOS 10.5 </span><a id="cupsSideChannelRead">cupsSideChannelRead</a></h3>
+
<p class="description">Read a side-channel message.</p>
<p class="code">
-int cupsSideChannelRead (<br>
- <a href="#cups_sc_command_t">cups_sc_command_t</a> *command,<br>
- <a href="#cups_sc_status_t">cups_sc_status_t</a> *status,<br>
- char *data,<br>
- int *datalen,<br>
- double timeout<br>
-);</p>
+int cupsSideChannelRead(<a href="#cups_sc_command_t">cups_sc_command_t</a> *command, <a href="#cups_sc_status_t">cups_sc_status_t</a> *status, char *data, int *datalen, double timeout);</p>
<h4 class="parameters">Parameters</h4>
-<dl>
-<dt>command</dt>
-<dd class="description">Command code</dd>
-<dt>status</dt>
-<dd class="description">Status code</dd>
-<dt>data</dt>
-<dd class="description">Data buffer pointer</dd>
-<dt>datalen</dt>
-<dd class="description">Size of data buffer on entry, number of bytes in buffer on return</dd>
-<dt>timeout</dt>
-<dd class="description">Timeout in seconds</dd>
-</dl>
+<table class="list"><tbody>
+<tr><th>command</th>
+ <td class="description">Command code</td></tr>
+<tr><th>status</th>
+ <td class="description">Status code</td></tr>
+<tr><th>data</th>
+ <td class="description">Data buffer pointer</td></tr>
+<tr><th>datalen</th>
+ <td class="description">Size of data buffer on entry, number of bytes in buffer on return</td></tr>
+<tr><th>timeout</th>
+ <td class="description">Timeout in seconds</td></tr>
+</tbody></table>
<h4 class="returnvalue">Return Value</h4>
-<p class="description">0 on success, -1 on error</p>
+
<p class="description">0 on success, -1 on error</p>
<h4 class="discussion">Discussion</h4>
-<p class="discussion">This function is normally only called by backend programs to read
+
<p class="discussion">This function is normally only called by backend programs to read
commands from a filter, driver, or port monitor program. The
caller must be prepared to handle incomplete or invalid messages
and return the corresponding status codes.<br>
update the value to contain the number of data bytes in the buffer.
</p>
-<h3 class="function"><span class="info"> CUPS 1.4 </span><a name="cupsSideChannelSNMPGet">cupsSideChannelSNMPGet</a></h3>
-<p class="description">Query a SNMP OID's value.</p>
+<h3 class="function"><span class="info"> CUPS 1.4/macOS 10.6 </span><a id="cupsSideChannelSNMPGet">cupsSideChannelSNMPGet</a></h3>
+
<p class="description">Query a SNMP OID's value.</p>
<p class="code">
-<a href="#cups_sc_status_t">cups_sc_status_t</a> cupsSideChannelSNMPGet (<br>
- const char *oid,<br>
- char *data,<br>
- int *datalen,<br>
- double timeout<br>
-);</p>
+<a href="#cups_sc_status_t">cups_sc_status_t</a> cupsSideChannelSNMPGet(const char *oid, char *data, int *datalen, double timeout);</p>
<h4 class="parameters">Parameters</h4>
-<dl>
-<dt>oid</dt>
-<dd class="description">OID to query</dd>
-<dt>data</dt>
-<dd class="description">Buffer for OID value</dd>
-<dt>datalen</dt>
-<dd class="description">Size of OID buffer on entry, size of value on return</dd>
-<dt>timeout</dt>
-<dd class="description">Timeout in seconds</dd>
-</dl>
+<table class="list"><tbody>
+<tr><th>oid</th>
+ <td class="description">OID to query</td></tr>
+<tr><th>data</th>
+ <td class="description">Buffer for OID value</td></tr>
+<tr><th>datalen</th>
+ <td class="description">Size of OID buffer on entry, size of value on return</td></tr>
+<tr><th>timeout</th>
+ <td class="description">Timeout in seconds</td></tr>
+</tbody></table>
<h4 class="returnvalue">Return Value</h4>
-<p class="description">Query status</p>
+
<p class="description">Query status</p>
<h4 class="discussion">Discussion</h4>
-<p class="discussion">This function asks the backend to do a SNMP OID query on behalf of the
+
<p class="discussion">This function asks the backend to do a SNMP OID query on behalf of the
filter, port monitor, or backend using the default community name.<br>
<br>
"oid" contains a numeric OID consisting of integers separated by periods,
the printer does not respond to the SNMP query.
</p>
-<h3 class="function"><span class="info"> CUPS 1.4 </span><a name="cupsSideChannelSNMPWalk">cupsSideChannelSNMPWalk</a></h3>
-<p class="description">Query multiple SNMP OID values.</p>
+<h3 class="function"><span class="info"> CUPS 1.4/macOS 10.6 </span><a id="cupsSideChannelSNMPWalk">cupsSideChannelSNMPWalk</a></h3>
+
<p class="description">Query multiple SNMP OID values.</p>
<p class="code">
-<a href="#cups_sc_status_t">cups_sc_status_t</a> cupsSideChannelSNMPWalk (<br>
- const char *oid,<br>
- double timeout,<br>
- <a href="#cups_sc_walk_func_t">cups_sc_walk_func_t</a> cb,<br>
- void *context<br>
-);</p>
+<a href="#cups_sc_status_t">cups_sc_status_t</a> cupsSideChannelSNMPWalk(const char *oid, double timeout, <a href="#cups_sc_walk_func_t">cups_sc_walk_func_t</a> cb, void *context);</p>
<h4 class="parameters">Parameters</h4>
-<dl>
-<dt>oid</dt>
-<dd class="description">First numeric OID to query</dd>
-<dt>timeout</dt>
-<dd class="description">Timeout for each query in seconds</dd>
-<dt>cb</dt>
-<dd class="description">Function to call with each value</dd>
-<dt>context</dt>
-<dd class="description">Application-defined pointer to send to callback</dd>
-</dl>
+<table class="list"><tbody>
+<tr><th>oid</th>
+ <td class="description">First numeric OID to query</td></tr>
+<tr><th>timeout</th>
+ <td class="description">Timeout for each query in seconds</td></tr>
+<tr><th>cb</th>
+ <td class="description">Function to call with each value</td></tr>
+<tr><th>context</th>
+ <td class="description">Application-defined pointer to send to callback</td></tr>
+</tbody></table>
<h4 class="returnvalue">Return Value</h4>
-<p class="description">Status of first query of <code>CUPS_SC_STATUS_OK</code> on success</p>
+
<p class="description">Status of first query of <code>CUPS_SC_STATUS_OK</code> on success</p>
<h4 class="discussion">Discussion</h4>
-<p class="discussion">This function asks the backend to do multiple SNMP OID queries on behalf
+
<p class="discussion">This function asks the backend to do multiple SNMP OID queries on behalf
of the filter, port monitor, or backend using the default community name.
All OIDs under the "parent" OID are queried and the results are sent to
the callback function you provide.<br>
the printer does not respond to the first SNMP query.
</p>
-<h3 class="function"><span class="info"> CUPS 1.3/Mac OS X 10.5 </span><a name="cupsSideChannelWrite">cupsSideChannelWrite</a></h3>
-<p class="description">Write a side-channel message.</p>
+<h3 class="function"><span class="info"> CUPS 1.3/macOS 10.5 </span><a id="cupsSideChannelWrite">cupsSideChannelWrite</a></h3>
+
<p class="description">Write a side-channel message.</p>
<p class="code">
-int cupsSideChannelWrite (<br>
- <a href="#cups_sc_command_t">cups_sc_command_t</a> command,<br>
- <a href="#cups_sc_status_t">cups_sc_status_t</a> status,<br>
- const char *data,<br>
- int datalen,<br>
- double timeout<br>
-);</p>
+int cupsSideChannelWrite(<a href="#cups_sc_command_t">cups_sc_command_t</a> command, <a href="#cups_sc_status_t">cups_sc_status_t</a> status, const char *data, int datalen, double timeout);</p>
<h4 class="parameters">Parameters</h4>
-<dl>
-<dt>command</dt>
-<dd class="description">Command code</dd>
-<dt>status</dt>
-<dd class="description">Status code</dd>
-<dt>data</dt>
-<dd class="description">Data buffer pointer</dd>
-<dt>datalen</dt>
-<dd class="description">Number of bytes of data</dd>
-<dt>timeout</dt>
-<dd class="description">Timeout in seconds</dd>
-</dl>
+<table class="list"><tbody>
+<tr><th>command</th>
+ <td class="description">Command code</td></tr>
+<tr><th>status</th>
+ <td class="description">Status code</td></tr>
+<tr><th>data</th>
+ <td class="description">Data buffer pointer</td></tr>
+<tr><th>datalen</th>
+ <td class="description">Number of bytes of data</td></tr>
+<tr><th>timeout</th>
+ <td class="description">Timeout in seconds</td></tr>
+</tbody></table>
<h4 class="returnvalue">Return Value</h4>
-<p class="description">0 on success, -1 on error</p>
+
<p class="description">0 on success, -1 on error</p>
<h4 class="discussion">Discussion</h4>
-<p class="discussion">This function is normally only called by backend programs to send
+
<p class="discussion">This function is normally only called by backend programs to send
responses to a filter, driver, or port monitor program.
</p>
-<h2 class="title"><a name="TYPES">Data Types</a></h2>
-<h3 class="typedef"><a name="cups_backend_t">cups_backend_t</a></h3>
-<p class="description">Backend exit codes</p>
-<p class="code">
+ <h2 class="title"><a id="TYPES">Data Types</a></h2>
+ <h3 class="typedef"><a id="cups_backend_t">cups_backend_t</a></h3>
+
<p class="description">Backend exit codes</p>
typedef enum <a href="#cups_backend_e">cups_backend_e</a> cups_backend_t;
</p>
-<h3 class="typedef"><a name="cups_sc_bidi_t">cups_sc_bidi_t</a></h3>
-<p class="description">Bidirectional capabilities</p>
-<p class="code">
+ <h3 class="typedef"><a id="cups_sc_bidi_t">cups_sc_bidi_t</a></h3>
+
<p class="description">Bidirectional capabilities</p>
typedef enum <a href="#cups_sc_bidi_e">cups_sc_bidi_e</a> cups_sc_bidi_t;
</p>
-<h3 class="typedef"><a name="cups_sc_command_t">cups_sc_command_t</a></h3>
-<p class="description">Request command codes</p>
-<p class="code">
+ <h3 class="typedef"><a id="cups_sc_command_t">cups_sc_command_t</a></h3>
+
<p class="description">Request command codes</p>
typedef enum <a href="#cups_sc_command_e">cups_sc_command_e</a> cups_sc_command_t;
</p>
-<h3 class="typedef"><a name="cups_sc_state_t">cups_sc_state_t</a></h3>
-<p class="description">Printer state bits</p>
-<p class="code">
+ <h3 class="typedef"><a id="cups_sc_connected_t">cups_sc_connected_t</a></h3>
+ <p class="description">Connectivity values</p>
+ <p class="code">
+typedef enum <a href="#cups_sc_connected_e">cups_sc_connected_e</a> cups_sc_connected_t;
+</p>
+ <h3 class="typedef"><a id="cups_sc_state_t">cups_sc_state_t</a></h3>
+ <p class="description">Printer state bits</p>
+ <p class="code">
typedef enum <a href="#cups_sc_state_e">cups_sc_state_e</a> cups_sc_state_t;
</p>
-<h3 class="typedef"><a name="cups_sc_status_t">cups_sc_status_t</a></h3>
-<p class="description">Response status codes</p>
-<p class="code">
+ <h3 class="typedef"><a id="cups_sc_status_t">cups_sc_status_t</a></h3>
+
<p class="description">Response status codes</p>
typedef enum <a href="#cups_sc_status_e">cups_sc_status_e</a> cups_sc_status_t;
</p>
-<h3 class="typedef"><a name="cups_sc_walk_func_t">cups_sc_walk_func_t</a></h3>
-<p class="description">SNMP walk callback</p>
-<p class="code">
+ <h3 class="typedef"><a id="cups_sc_walk_func_t">cups_sc_walk_func_t</a></h3>
+
<p class="description">SNMP walk callback</p>
typedef void (*cups_sc_walk_func_t)(const char *oid, const char *data, int datalen, void *context);
</p>
-<h2 class="title"><a name="ENUMERATIONS">Constants</a></h2>
-<h3 class="enumeration"><a name="cups_backend_e">cups_backend_e</a></h3>
-<p class="description">Backend exit codes</p>
-<h4 class="constants">Constants</h4>
-<dl>
-<dt>CUPS_BACKEND_AUTH_REQUIRED </dt>
-<dd class="description">Job failed, authentication required</dd>
-<dt>CUPS_BACKEND_CANCEL </dt>
-<dd class="description">Job failed, cancel job</dd>
-<dt>CUPS_BACKEND_FAILED </dt>
-<dd class="description">Job failed, use error-policy</dd>
-<dt>CUPS_BACKEND_HOLD </dt>
-<dd class="description">Job failed, hold job</dd>
-<dt>CUPS_BACKEND_OK </dt>
-<dd class="description">Job completed successfully</dd>
-<dt>CUPS_BACKEND_STOP </dt>
-<dd class="description">Job failed, stop queue</dd>
-</dl>
-<h3 class="enumeration"><a name="cups_sc_bidi_e">cups_sc_bidi_e</a></h3>
-<p class="description">Bidirectional capability values</p>
-<h4 class="constants">Constants</h4>
-<dl>
-<dt>CUPS_SC_BIDI_NOT_SUPPORTED </dt>
-<dd class="description">Bidirectional I/O is not supported</dd>
-<dt>CUPS_SC_BIDI_SUPPORTED </dt>
-<dd class="description">Bidirectional I/O is supported</dd>
-</dl>
-<h3 class="enumeration"><a name="cups_sc_command_e">cups_sc_command_e</a></h3>
-<p class="description">Request command codes</p>
-<h4 class="constants">Constants</h4>
-<dl>
-<dt>CUPS_SC_CMD_DRAIN_OUTPUT </dt>
-<dd class="description">Drain all pending output</dd>
-<dt>CUPS_SC_CMD_GET_BIDI </dt>
-<dd class="description">Return bidirectional capabilities</dd>
-<dt>CUPS_SC_CMD_GET_DEVICE_ID </dt>
-<dd class="description">Return the IEEE-1284 device ID</dd>
-<dt>CUPS_SC_CMD_GET_STATE </dt>
-<dd class="description">Return the device state</dd>
-<dt>CUPS_SC_CMD_SNMP_GET <span class="info"> CUPS 1.4 </span></dt>
-<dd class="description">Query an SNMP OID </dd>
-<dt>CUPS_SC_CMD_SNMP_GET_NEXT <span class="info"> CUPS 1.4 </span></dt>
-<dd class="description">Query the next SNMP OID </dd>
-<dt>CUPS_SC_CMD_SOFT_RESET </dt>
-<dd class="description">Do a soft reset</dd>
-</dl>
-<h3 class="enumeration"><a name="cups_sc_state_e">cups_sc_state_e</a></h3>
-<p class="description">Printer state bits</p>
-<h4 class="constants">Constants</h4>
-<dl>
-<dt>CUPS_SC_STATE_BUSY </dt>
-<dd class="description">Device is busy</dd>
-<dt>CUPS_SC_STATE_ERROR </dt>
-<dd class="description">Other error condition</dd>
-<dt>CUPS_SC_STATE_MARKER_EMPTY </dt>
-<dd class="description">Toner/ink out condition</dd>
-<dt>CUPS_SC_STATE_MARKER_LOW </dt>
-<dd class="description">Toner/ink low condition</dd>
-<dt>CUPS_SC_STATE_MEDIA_EMPTY </dt>
-<dd class="description">Paper out condition</dd>
-<dt>CUPS_SC_STATE_MEDIA_LOW </dt>
-<dd class="description">Paper low condition</dd>
-<dt>CUPS_SC_STATE_OFFLINE </dt>
-<dd class="description">Device is offline</dd>
-<dt>CUPS_SC_STATE_ONLINE </dt>
-<dd class="description">Device is online</dd>
-</dl>
-<h3 class="enumeration"><a name="cups_sc_status_e">cups_sc_status_e</a></h3>
-<p class="description">Response status codes</p>
-<h4 class="constants">Constants</h4>
-<dl>
-<dt>CUPS_SC_STATUS_BAD_MESSAGE </dt>
-<dd class="description">The command/response message was invalid</dd>
-<dt>CUPS_SC_STATUS_IO_ERROR </dt>
-<dd class="description">An I/O error occurred</dd>
-<dt>CUPS_SC_STATUS_NONE </dt>
-<dd class="description">No status</dd>
-<dt>CUPS_SC_STATUS_NOT_IMPLEMENTED </dt>
-<dd class="description">Command not implemented</dd>
-<dt>CUPS_SC_STATUS_NO_RESPONSE </dt>
-<dd class="description">The device did not respond</dd>
-<dt>CUPS_SC_STATUS_OK </dt>
-<dd class="description">Operation succeeded</dd>
-<dt>CUPS_SC_STATUS_TIMEOUT </dt>
-<dd class="description">The backend did not respond</dd>
-<dt>CUPS_SC_STATUS_TOO_BIG </dt>
-<dd class="description">Response too big</dd>
-</dl>
-</div>
-</body>
+ <h2 class="title"><a id="ENUMERATIONS">Constants</a></h2>
+ <h3 class="enumeration"><a id="cups_backend_e">cups_backend_e</a></h3>
+ <p class="description">Backend exit codes</p>
+ <h4 class="constants">Constants</h4>
+ <table class="list"><tbody>
+ <tr><th>CUPS_BACKEND_AUTH_REQUIRED </th> <td class="description">Job failed, authentication required</td></tr>
+ <tr><th>CUPS_BACKEND_CANCEL </th> <td class="description">Job failed, cancel job</td></tr>
+ <tr><th>CUPS_BACKEND_FAILED </th> <td class="description">Job failed, use error-policy</td></tr>
+ <tr><th>CUPS_BACKEND_HOLD </th> <td class="description">Job failed, hold job</td></tr>
+ <tr><th>CUPS_BACKEND_OK </th> <td class="description">Job completed successfully</td></tr>
+ <tr><th>CUPS_BACKEND_RETRY </th> <td class="description">Job failed, retry this job later</td></tr>
+ <tr><th>CUPS_BACKEND_RETRY_CURRENT </th> <td class="description">Job failed, retry this job immediately</td></tr>
+ <tr><th>CUPS_BACKEND_STOP </th> <td class="description">Job failed, stop queue</td></tr>
+</tbody></table>
+ <h3 class="enumeration"><a id="cups_sc_bidi_e">cups_sc_bidi_e</a></h3>
+ <p class="description">Bidirectional capability values</p>
+ <h4 class="constants">Constants</h4>
+ <table class="list"><tbody>
+ <tr><th>CUPS_SC_BIDI_NOT_SUPPORTED </th> <td class="description">Bidirectional I/O is not supported</td></tr>
+ <tr><th>CUPS_SC_BIDI_SUPPORTED </th> <td class="description">Bidirectional I/O is supported</td></tr>
+</tbody></table>
+ <h3 class="enumeration"><a id="cups_sc_command_e">cups_sc_command_e</a></h3>
+ <p class="description">Request command codes</p>
+ <h4 class="constants">Constants</h4>
+ <table class="list"><tbody>
+ <tr><th>CUPS_SC_CMD_DRAIN_OUTPUT </th> <td class="description">Drain all pending output</td></tr>
+ <tr><th>CUPS_SC_CMD_GET_BIDI </th> <td class="description">Return bidirectional capabilities</td></tr>
+ <tr><th>CUPS_SC_CMD_GET_CONNECTED <span class="info"> CUPS 1.5/macOS 10.7 </span></th> <td class="description">Return whether the backend is "connected" to the printer </td></tr>
+ <tr><th>CUPS_SC_CMD_GET_DEVICE_ID </th> <td class="description">Return the IEEE-1284 device ID</td></tr>
+ <tr><th>CUPS_SC_CMD_GET_STATE </th> <td class="description">Return the device state</td></tr>
+ <tr><th>CUPS_SC_CMD_SNMP_GET <span class="info"> CUPS 1.4/macOS 10.6 </span></th> <td class="description">Query an SNMP OID </td></tr>
+ <tr><th>CUPS_SC_CMD_SNMP_GET_NEXT <span class="info"> CUPS 1.4/macOS 10.6 </span></th> <td class="description">Query the next SNMP OID </td></tr>
+ <tr><th>CUPS_SC_CMD_SOFT_RESET </th> <td class="description">Do a soft reset</td></tr>
+</tbody></table>
+ <h3 class="enumeration"><a id="cups_sc_connected_e">cups_sc_connected_e</a></h3>
+ <p class="description">Connectivity values</p>
+ <h4 class="constants">Constants</h4>
+ <table class="list"><tbody>
+ <tr><th>CUPS_SC_CONNECTED </th> <td class="description">Backend is "connected" to printer</td></tr>
+ <tr><th>CUPS_SC_NOT_CONNECTED </th> <td class="description">Backend is not "connected" to printer</td></tr>
+</tbody></table>
+ <h3 class="enumeration"><a id="cups_sc_state_e">cups_sc_state_e</a></h3>
+ <p class="description">Printer state bits</p>
+ <h4 class="constants">Constants</h4>
+ <table class="list"><tbody>
+ <tr><th>CUPS_SC_STATE_BUSY </th> <td class="description">Device is busy</td></tr>
+ <tr><th>CUPS_SC_STATE_ERROR </th> <td class="description">Other error condition</td></tr>
+ <tr><th>CUPS_SC_STATE_MARKER_EMPTY </th> <td class="description">Toner/ink out condition</td></tr>
+ <tr><th>CUPS_SC_STATE_MARKER_LOW </th> <td class="description">Toner/ink low condition</td></tr>
+ <tr><th>CUPS_SC_STATE_MEDIA_EMPTY </th> <td class="description">Paper out condition</td></tr>
+ <tr><th>CUPS_SC_STATE_MEDIA_LOW </th> <td class="description">Paper low condition</td></tr>
+ <tr><th>CUPS_SC_STATE_OFFLINE </th> <td class="description">Device is offline</td></tr>
+ <tr><th>CUPS_SC_STATE_ONLINE </th> <td class="description">Device is online</td></tr>
+</tbody></table>
+ <h3 class="enumeration"><a id="cups_sc_status_e">cups_sc_status_e</a></h3>
+ <p class="description">Response status codes</p>
+ <h4 class="constants">Constants</h4>
+ <table class="list"><tbody>
+ <tr><th>CUPS_SC_STATUS_BAD_MESSAGE </th> <td class="description">The command/response message was invalid</td></tr>
+ <tr><th>CUPS_SC_STATUS_IO_ERROR </th> <td class="description">An I/O error occurred</td></tr>
+ <tr><th>CUPS_SC_STATUS_NONE </th> <td class="description">No status</td></tr>
+ <tr><th>CUPS_SC_STATUS_NOT_IMPLEMENTED </th> <td class="description">Command not implemented</td></tr>
+ <tr><th>CUPS_SC_STATUS_NO_RESPONSE </th> <td class="description">The device did not respond</td></tr>
+ <tr><th>CUPS_SC_STATUS_OK </th> <td class="description">Operation succeeded</td></tr>
+ <tr><th>CUPS_SC_STATUS_TIMEOUT </th> <td class="description">The backend did not respond</td></tr>
+ <tr><th>CUPS_SC_STATUS_TOO_BIG </th> <td class="description">Response too big</td></tr>
+</tbody></table>
+ </div>
+ </body>
</html>
projects / thirdparty / cups.git / blobdiff