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</style><title>FAQ</title></head><body bgcolor="#8b7765" text="#000000" link="#a06060" vlink="#000000"><table border="0" width="100%" cellpadding="5" cellspacing="0" align="center"><tr><td width="120"><a href="http://swpat.ffii.org/"><img src="epatents.png" alt="Action against software patents" /></a></td><td width="180"><a href="http://www.gnome.org/"><img src="gnome2.png" alt="Gnome2 Logo" /></a><a href="http://www.w3.org/Status"><img src="w3c.png" alt="W3C Logo" /></a><a href="http://www.redhat.com/"><img src="redhat.gif" alt="Red Hat Logo" /></a><div align="left"><a href="http://xmlsoft.org/"><img src="Libxml2-Logo-180x168.gif" alt="Made with Libxml2 Logo" /></a></div></td><td><table border="0" width="90%" cellpadding="2" cellspacing="0" align="center" bgcolor="#000000"><tr><td><table width="100%" border="0" cellspacing="1" cellpadding="3" bgcolor="#fffacd"><tr><td align="center"><h1>The XML C parser and toolkit of Gnome</h1><h2>FAQ</h2></td></tr></table></td></tr></table></td></tr></table><table border="0" cellpadding="4" cellspacing="0" width="100%" align="center"><tr><td bgcolor="#8b7765"><table border="0" cellspacing="0" cellpadding="2" width="100%"><tr><td valign="top" width="200" bgcolor="#8b7765"><table border="0" cellspacing="0" cellpadding="1" width="100%" bgcolor="#000000"><tr><td><table width="100%" border="0" cellspacing="1" cellpadding="3"><tr><td colspan="1" bgcolor="#eecfa1" align="center"><center>Main Menu</center></td></tr><tr><td bgcolor="#fffacd"><form action="search.php" enctype="application/x-www-form-urlencoded" method="get"><input name="query" type="text" size="20" value="" /><input name="submit" type="submit" value="Search ..." /></form><ul><li><a href="index.html">Home</a></li><li><a href="html/index.html">Reference Manual</a></li><li><a href="intro.html">Introduction</a></li><li><a href="FAQ.html">FAQ</a></li><li><a href="docs.html" style="font-weight:bold">Developer Menu</a></li><li><a href="bugs.html">Reporting bugs and getting help</a></li><li><a href="help.html">How to help</a></li><li><a href="downloads.html">Downloads</a></li><li><a href="news.html">Releases</a></li><li><a href="XMLinfo.html">XML</a></li><li><a href="XSLT.html">XSLT</a></li><li><a href="xmldtd.html">Validation &amp; DTDs</a></li><li><a href="encoding.html">Encodings support</a></li><li><a href="catalog.html">Catalog support</a></li><li><a href="namespaces.html">Namespaces</a></li><li><a href="contribs.html">Contributions</a></li><li><a href="examples/index.html" style="font-weight:bold">Code Examples</a></li><li><a href="html/index.html" style="font-weight:bold">API Menu</a></li><li><a href="guidelines.html">XML Guidelines</a></li><li><a href="ChangeLog.html">Recent Changes</a></li></ul></td></tr></table><table width="100%" border="0" cellspacing="1" cellpadding="3"><tr><td colspan="1" bgcolor="#eecfa1" align="center"><center>Related links</center></td></tr><tr><td bgcolor="#fffacd"><ul><li><a href="http://mail.gnome.org/archives/xml/">Mail archive</a></li><li><a href="http://xmlsoft.org/XSLT/">XSLT libxslt</a></li><li><a href="http://phd.cs.unibo.it/gdome2/">DOM gdome2</a></li><li><a href="http://www.aleksey.com/xmlsec/">XML-DSig xmlsec</a></li><li><a href="ftp://xmlsoft.org/">FTP</a></li><li><a href="http://www.zlatkovic.com/projects/libxml/">Windows binaries</a></li><li><a href="http://opencsw.org/packages/libxml2">Solaris binaries</a></li><li><a href="http://www.explain.com.au/oss/libxml2xslt.html">MacOsX binaries</a></li><li><a href="http://codespeak.net/lxml/">lxml Python bindings</a></li><li><a href="http://cpan.uwinnipeg.ca/dist/XML-LibXML">Perl bindings</a></li><li><a href="http://libxmlplusplus.sourceforge.net/">C++ bindings</a></li><li><a href="http://www.zend.com/php5/articles/php5-xmlphp.php#Heading4">PHP bindings</a></li><li><a href="http://sourceforge.net/projects/libxml2-pas/">Pascal bindings</a></li><li><a href="http://libxml.rubyforge.org/">Ruby bindings</a></li><li><a href="http://tclxml.sourceforge.net/">Tcl bindings</a></li><li><a href="http://bugzilla.gnome.org/buglist.cgi?product=libxml2">Bug Tracker</a></li></ul></td></tr></table></td></tr></table></td><td valign="top" bgcolor="#8b7765"><table border="0" cellspacing="0" cellpadding="1" width="100%"><tr><td><table border="0" cellspacing="0" cellpadding="1" width="100%" bgcolor="#000000"><tr><td><table border="0" cellpadding="3" cellspacing="1" width="100%"><tr><td bgcolor="#fffacd">Table of Contents:<ul><li><a href="FAQ.html#License">License(s)</a></li>
 <li><a href="FAQ.html#Installati">Installation</a></li>
 <li><a href="FAQ.html#Compilatio">Compilation</a></li>
 <li><a href="FAQ.html#Developer">Developer corner</a></li>
</ul><h3><a name="License" id="License">License</a>(s)</h3><ol><li>Licensing Terms for libxml
 libxml2 is released under the <a href="http://www.opensource.org/licenses/mit-license.html">MIT
 License</a>; see the file Copyright in the distribution for the precise
 wording
 </li>
 <li>Can I embed libxml2 in a proprietary application ?
 Yes. The MIT License allows you to keep proprietary the changes you
 made to libxml, but it would be graceful to send-back bug fixes and
 improvements as patches for possible incorporation in the main
 development tree.
 </li>
</ol><h3><a name="Installati" id="Installati">Installation</a></h3><ol><li>Do Not Use
 libxml1, use libxml2</li>
 
 <li>Where can I get libxml ?
 The original distribution comes from <a href="ftp://xmlsoft.org/libxml2/">xmlsoft.org</a> or <a href="ftp://ftp.gnome.org/pub/GNOME/sources/libxml2/2.6/">gnome.org</a>
 Most Linux and BSD distributions include libxml, this is probably the
 safer way for end-users to use libxml.
 David Doolin provides precompiled Windows versions at <a href="http://www.ce.berkeley.edu/~doolin/code/libxmlwin32/ ">http://www.ce.berkeley.edu/~doolin/code/libxmlwin32/</a>
 </li>
 
 <li>I see libxml and libxml2 releases, which one should I install ?
 <ul><li>If you are not constrained by backward compatibility issues with
 existing applications, install libxml2 only</li>
 <li>If you are not doing development, you can safely install both.
 Usually the packages <a href="http://rpmfind.net/linux/RPM/libxml.html">libxml</a> and <a href="http://rpmfind.net/linux/RPM/libxml2.html">libxml2</a> are
 compatible (this is not the case for development packages).</li>
 <li>If you are a developer and your system provides separate packaging
 for shared libraries and the development components, it is possible
 to install libxml and libxml2, and also <a href="http://rpmfind.net/linux/RPM/libxml-devel.html">libxml-devel</a>
 and <a href="http://rpmfind.net/linux/RPM/libxml2-devel.html">libxml2-devel</a>
 too for libxml2 &gt;= 2.3.0</li>
 <li>If you are developing a new application, please develop against
 libxml2(-devel)</li>
 </ul></li>
 <li>I can't install the libxml package, it conflicts with libxml0
 You probably have an old libxml0 package used to provide the shared
 library for libxml.so.0, you can probably safely remove it. The libxml
 packages provided on <a href="ftp://xmlsoft.org/libxml2/">xmlsoft.org</a> provide
 libxml.so.0
 </li>
 <li>I can't install the libxml(2) RPM package due to failed
 dependencies
 The most generic solution is to re-fetch the latest src.rpm , and
 rebuild it locally with
 <code>rpm --rebuild libxml(2)-xxx.src.rpm</code>.
 If everything goes well it will generate two binary rpm packages (one
 providing the shared libs and xmllint, and the other one, the -devel
 package, providing includes, static libraries and scripts needed to build
 applications with libxml(2)) that you can install locally.
 </li>
</ol><h3><a name="Compilatio" id="Compilatio">Compilation</a></h3><ol><li>What is the process to compile libxml2 ?
 As most UNIX libraries libxml2 follows the "standard":
 <code>gunzip -c xxx.tar.gz | tar xvf -</code>
 <code>cd libxml-xxxx</code>
 <code>./configure --help</code>
 to see the options, then the compilation/installation proper
 <code>./configure [possible options]</code>
 <code>make</code>
 <code>make install</code>
 At that point you may have to rerun ldconfig or a similar utility to
 update your list of installed shared libs.
 </li>
 <li>What other libraries are needed to compile/install libxml2 ?
 Libxml2 does not require any other library, the normal C ANSI API
 should be sufficient (please report any violation to this rule you may
 find).
 However if found at configuration time libxml2 will detect and use the
 following libs:
 <ul><li><a href="http://www.info-zip.org/pub/infozip/zlib/">libz</a> : a
 highly portable and available widely compression library.</li>
 <li>iconv: a powerful character encoding conversion library. It is
 included by default in recent glibc libraries, so it doesn't need to
 be installed specifically on Linux. It now seems a <a href="http://www.opennc.org/onlinepubs/7908799/xsh/iconv.html">part
 of the official UNIX</a> specification. Here is one <a href="http://www.gnu.org/software/libiconv/">implementation of the
 library</a> which source can be found <a href="ftp://ftp.ilog.fr/pub/Users/haible/gnu/">here</a>.</li>
 </ul></li>
 
 <li>Make check fails on some platforms
 Sometimes the regression tests' results don't completely match the
 value produced by the parser, and the makefile uses diff to print the
 delta. On some platforms the diff return breaks the compilation process;
 if the diff is small this is probably not a serious problem.
 Sometimes (especially on Solaris) make checks fail due to limitations
 in make. Try using GNU-make instead.
 </li>
 <li>I use the SVN version and there is no configure script
 The configure script (and other Makefiles) are generated. Use the
 autogen.sh script to regenerate the configure script and Makefiles,
 like:
 <code>./autogen.sh --prefix=/usr --disable-shared</code>
 </li>
 <li>I have troubles when running make tests with gcc-3.0
 It seems the initial release of gcc-3.0 has a problem with the
 optimizer which miscompiles the URI module. Please use another
 compiler.
 </li>
</ol><h3><a name="Developer" id="Developer">Developer</a> corner</h3><ol><li>Troubles compiling or linking programs using libxml2
 Usually the problem comes from the fact that the compiler doesn't get
 the right compilation or linking flags. There is a small shell script
 <code>xml2-config</code> which is installed as part of libxml2 usual
 install process which provides those flags. Use
 <code>xml2-config --cflags</code>
 to get the compilation flags and
 <code>xml2-config --libs</code>
 to get the linker flags. Usually this is done directly from the
 Makefile as:
 <code>CFLAGS=`xml2-config --cflags`</code>
 <code>LIBS=`xml2-config --libs`</code>
 </li>
 <li>I want to install my own copy of libxml2 in my home directory and
 link my programs against it, but it doesn't work
 There are many different ways to accomplish this. Here is one way to
 do this under Linux. Suppose your home directory is <code>/home/user.
 </code>Then:
 <ul><li>Create a subdirectory, let's call it <code>myxml</code></li>
 <li>unpack the libxml2 distribution into that subdirectory</li>
 <li>chdir into the unpacked distribution
 (<code>/home/user/myxml/libxml2 </code>)</li>
 <li>configure the library using the "<code>--prefix</code>" switch,
 specifying an installation subdirectory in
 <code>/home/user/myxml</code>, e.g.
 <code>./configure --prefix /home/user/myxml/xmlinst</code> {other
 configuration options}
 </li>
 <li>now run <code>make</code> followed by <code>make install</code></li>
 <li>At this point, the installation subdirectory contains the complete
 "private" include files, library files and binary program files (e.g.
 xmllint), located in
 <code>/home/user/myxml/xmlinst/lib,
 /home/user/myxml/xmlinst/include </code> and <code>
 /home/user/myxml/xmlinst/bin</code>
 respectively.</li>
 <li>In order to use this "private" library, you should first add it to
 the beginning of your default PATH (so that your own private program
 files such as xmllint will be used instead of the normal system
 ones). To do this, the Bash command would be
 <code>export PATH=/home/user/myxml/xmlinst/bin:$PATH</code>
 </li>
 <li>Now suppose you have a program <code>test1.c</code> that you would
 like to compile with your "private" library. Simply compile it using
 the command
 <code>gcc `xml2-config --cflags --libs` -o test test.c</code>
 Note that, because your PATH has been set with <code>
 /home/user/myxml/xmlinst/bin</code> at the beginning, the xml2-config
 program which you just installed will be used instead of the system
 default one, and this will automatically get the correct
 libraries linked with your program.</li>
 </ul></li>

<li>xmlDocDump() generates output on one line.
 Libxml2 will not invent spaces in the content of a
 document since all spaces in the content of a document are
 significant. If you build a tree from the API and want
 indentation:
 <ol><li>the correct way is to generate those yourself too.</li>
 <li>the dangerous way is to ask libxml2 to add those blanks to your
 content modifying the content of your document in the
 process. The result may not be what you expect. There is
 NO way to guarantee that such a modification won't
 affect other parts of the content of your document. See <a href="http://xmlsoft.org/html/libxml-parser.html#xmlKeepBlanksDefault">xmlKeepBlanksDefault
 ()</a> and <a href="http://xmlsoft.org/html/libxml-tree.html#xmlSaveFormatFile">xmlSaveFormatFile
 ()</a></li>
 </ol></li>
 
 <li>Extra nodes in the document:
 For an XML file as below:
 <pre>&lt;?xml version="1.0"?&gt;
&lt;PLAN xmlns="http://www.argus.ca/autotest/1.0/"&gt;
&lt;NODE CommFlag="0"/&gt;
&lt;NODE CommFlag="1"/&gt;
&lt;/PLAN&gt;</pre>
 after parsing it with the function
 pxmlDoc=xmlParseFile(...);
 I want to the get the content of the first node (node with the
 CommFlag="0")
 so I did it as following;
 <pre>xmlNodePtr pnode;
pnode=pxmlDoc-&gt;children-&gt;children;</pre>
 but it does not work. If I change it to
 <pre>pnode=pxmlDoc-&gt;children-&gt;children-&gt;next;</pre>
 then it works. Can someone explain it to me.
 
 In XML all characters in the content of the document are significant
 including blanks and formatting line breaks.
 The extra nodes you are wondering about are just that, text nodes with
 the formatting spaces which are part of the document but that people tend
 to forget. There is a function <a href="http://xmlsoft.org/html/libxml-parser.html">xmlKeepBlanksDefault
 ()</a> to remove those at parse time, but that's an heuristic, and its
 use should be limited to cases where you are certain there is no
 mixed-content in the document.
 </li>
 <li>I get compilation errors of existing code like when accessing
 root or child fields of nodes.
 You are compiling code developed for libxml version 1 and using a
 libxml2 development environment. Either switch back to libxml v1 devel or
 even better fix the code to compile with libxml2 (or both) by <a href="upgrade.html">following the instructions</a>.
 </li>
 <li>I get compilation errors about non existing
 xmlRootNode or xmlChildrenNode
 fields.
 The source code you are using has been <a href="upgrade.html">upgraded</a> to be able to compile with both libxml
 and libxml2, but you need to install a more recent version:
 libxml(-devel) &gt;= 1.8.8 or libxml2(-devel) &gt;= 2.1.0
 </li>
 <li>Random crashes in threaded applications
 Read and follow all advices on the <a href="threads.html">thread
 safety</a> page, and make 100% sure you never call xmlCleanupParser()
 while the library or an XML document might still be in use by another
 thread.
 </li>
 <li>The example provided in the web page does not compile.
 It's hard to maintain the documentation in sync with the code
 &lt;grin/&gt; ...
 Check the previous points 1/ and 2/ raised before, and please send
 patches.
 </li>
 <li>Where can I get more examples and information than provided on the
 web page?
 Ideally a libxml2 book would be nice. I have no such plan ... But you
 can:
 <ul><li>check more deeply the <a href="html/libxml-lib.html">existing
 generated doc</a></li>
 <li>have a look at <a href="examples/index.html">the set of
 examples</a>.</li>
 <li>look for examples of use for libxml2 function using the Gnome code
 or by asking on Google.</li>
 <li><a href="http://svn.gnome.org/viewvc/libxml2/trunk/">Browse
 the libxml2 source</a> , I try to write code as clean and documented
 as possible, so looking at it may be helpful. In particular the code
 of <a href="http://svn.gnome.org/viewvc/libxml2/trunk/xmllint.c?view=markup">xmllint.c</a> and of the various testXXX.c test programs should
 provide good examples of how to do things with the library.</li>
 </ul></li>
 
 <li>What about C++ ?
 libxml2 is written in pure C in order to allow easy reuse on a number
 of platforms, including embedded systems. I don't intend to convert to
 C++.
 There is however a C++ wrapper which may fulfill your needs:
 <ul><li>by Ari Johnson &lt;ari@btigate.com&gt;:
 Website: <a href="http://libxmlplusplus.sourceforge.net/">http://libxmlplusplus.sourceforge.net/</a>
 Download: <a href="http://sourceforge.net/project/showfiles.php?group_id=12999">http://sourceforge.net/project/showfiles.php?group_id=12999</a>
 </li>
 </ul></li>
 <li>How to validate a document a posteriori ?
 It is possible to validate documents which had not been validated at
 initial parsing time or documents which have been built from scratch
 using the API. Use the <a href="http://xmlsoft.org/html/libxml-valid.html#xmlValidateDtd">xmlValidateDtd()</a>
 function. It is also possible to simply add a DTD to an existing
 document:
 <pre>xmlDocPtr doc; /* your existing document */
xmlDtdPtr dtd = xmlParseDTD(NULL, filename_of_dtd); /* parse the DTD */

dtd-&gt;name = xmlStrDup((xmlChar*)"root_name"); /* use the given root */

doc-&gt;intSubset = dtd;
 if (doc-&gt;children == NULL) xmlAddChild((xmlNodePtr)doc, (xmlNodePtr)dtd);
 else xmlAddPrevSibling(doc-&gt;children, (xmlNodePtr)dtd);
 </pre>
 </li>
 <li>So what is this funky "xmlChar" used all the time?
 It is a null terminated sequence of utf-8 characters. And only utf-8!
 You need to convert strings encoded in different ways to utf-8 before
 passing them to the API. This can be accomplished with the iconv library
 for instance.
 </li>
 <li>etc ...</li>
</ol><a href="bugs.html">Daniel Veillard</a></td></tr></table></td></tr></table></td></tr></table></td></tr></table></td></tr></table></body></html>