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<!--
- "$Id: api-filter.header 7616 2008-05-28 00:34:13Z mike $"
+ "$Id$"
Filter and backend programming header for the Common UNIX Printing System
(CUPS).
- Copyright 2008 by Apple Inc.
+ Copyright 2008-2009 by Apple Inc.
These coded instructions, statements, and computer programs are the
property of Apple Inc. and are protected by Federal copyright
file is missing or damaged, see the license at "http://www.cups.org/".
-->
-<h1 class="title">Filter and Backend Programming</h1>
+<h1 class='title'>Filter and Backend Programming</h1>
<div class='summary'><table summary='General Information'>
<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>
+ 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' target='_top'>CUPS Design Description</a></td>
</tr>
</tbody>
</table></div>
<h2 class="title">Contents</h2>
<ul class="contents">
-</li>
+<ul class="subcontents">
<li><a href="#OVERVIEW">Overview</a><ul class="subcontents">
<li><a href="#SECURITY">Security Considerations</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="#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>
+</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_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>
-</ul>
<!--
- "$Id: api-filter.shtml 7677 2008-06-19 23:22:19Z mike $"
+ "$Id$"
Filter and backend programming introduction for the Common UNIX Printing
System (CUPS).
- Copyright 2007-2008 by Apple Inc.
+ Copyright 2007-2009 by Apple Inc.
Copyright 1997-2006 by Easy Software Products, all rights reserved.
These coded instructions, statements, and computer programs are the
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
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
+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>
</blockquote>
+<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>
<dt>CUPS_DATADIR</dt>
<dd>The directory where (read-only) CUPS data files can be found.</dd>
+ <dt>CUPS_FILETYPE</dt>
+ <dd>The type of file being printed: "job-sheet" for a banner page and
+ "document" for a regular print file.</dd>
+
<dt>CUPS_SERVERROOT</dt>
<dd>The root directory of the server.</dd>
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>
+ use vendor-prefixed ("com.acme.foo") keywords for custom states.
+
+ <blockquote><b>Note:</b>
+
+ <p>"STATE:" messages often provide visible alerts to the user. For example, on
+ Mac OS X 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>
+
+ </blockquote></dd>
<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>
<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 </span><a name="cupsBackChannelRead">cupsBackChannelRead</a></h3>
+<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>
<p class="code">
ssize_t cupsBackChannelRead (<br>
return immediately if there is no data, -1.0 to wait for data indefinitely.
</p>
-<h3 class="function"><span class="info"> CUPS 1.2 </span><a name="cupsBackChannelWrite">cupsBackChannelWrite</a></h3>
+<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>
<p class="code">
ssize_t cupsBackChannelWrite (<br>
indefinitely.
</p>
-<h3 class="function"><a name="cupsBackendDeviceURI">cupsBackendDeviceURI</a></h3>
+<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>
<p class="code">
const char *cupsBackendDeviceURI (<br>
<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"><a name="cupsBackendReport">cupsBackendReport</a></h3>
+first.
+
+</p>
+<h3 class="function"><span class="info"> CUPS 1.4/Mac OS X 10.6 </span><a name="cupsBackendReport">cupsBackendReport</a></h3>
<p class="description">Write a device line from a backend.</p>
<p class="code">
void cupsBackendReport (<br>
<h4 class="discussion">Discussion</h4>
<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 </span><a name="cupsSideChannelDoRequest">cupsSideChannelDoRequest</a></h3>
+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>
<p class="code">
<a href="#cups_sc_status_t">cups_sc_status_t</a> cupsSideChannelDoRequest (<br>
update the value to contain the number of data bytes in the buffer.
</p>
-<h3 class="function"><span class="info"> CUPS 1.3 </span><a name="cupsSideChannelRead">cupsSideChannelRead</a></h3>
+<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>
<p class="code">
int cupsSideChannelRead (<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>
+<h3 class="function"><span class="info"> CUPS 1.4
/Mac OS X 10.6 </span><a name="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>
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>
+<h3 class="function"><span class="info"> CUPS 1.4
/Mac OS X 10.6 </span><a name="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>
the printer does not respond to the first SNMP query.
</p>
-<h3 class="function"><span class="info"> CUPS 1.3 </span><a name="cupsSideChannelWrite">cupsSideChannelWrite</a></h3>
+<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>
<p class="code">
int cupsSideChannelWrite (<br>
<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>
+<dt>CUPS_SC_CMD_SNMP_GET <span class="info"> CUPS 1.4/Mac OS X 10.6 </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>
+<dt>CUPS_SC_CMD_SNMP_GET_NEXT <span class="info"> CUPS 1.4/Mac OS X 10.6 </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>
projects / thirdparty / cups.git / blobdiff