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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><b>Main Menu</b></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 & 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><b>Related links</b></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://www.blastwave.org/packages.php/libxml2">Solaris binaries</a></li><li><a href="http://www.explain.com.au/oss/libxml2xslt.html">MacOsX binaries</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"><p>Table of Contents:</p><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><em>Licensing Terms for libxml</em>
<p>libxml2 is released under the <a href="http://www.opensource.org/licenses/mit-license.html">MITLicense</a>;see
the file Copyright in the distribution for the precisewording</p>
</li>
<li><em>Can I embed libxml2 in a proprietary application ?</em>
<p>Yes. The MIT License allows you to keep proprietary the changesyoumade
to libxml, but it would be graceful to send-back bug fixesandimprovements
as patches for possible incorporation in themaindevelopment tree.</p>
</li>
</ol><h3><a name="Installati" id="Installati">Installation</a></h3><ol><li><strong><span style="background-color: #FF0000">Do
NotUselibxml1</span></strong>, use libxml2</li>
<li><em>Where can I get libxml</em>?
<p>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></p>
<p>Most Linux and BSD distributions include libxml, this is
probablythesafer way for end-users to use libxml.</p>
<p>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></p>
</li>
<li><em>I see libxml and libxml2 releases, which one should I install ?</em>
<ul><li>If you are not constrained by backward compatibility
issueswithexisting applications, install libxml2 only</li>
<li>If you are not doing development, you can safely
installboth.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>arecompatible(this
is not the case for development packages).</li>
<li>If you are a developer and your system provides
separatepackagingfor shared libraries and the development components,
it ispossibleto 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>toofor
libxml2 >= 2.3.0</li>
<li>If you are developing a new application, please
developagainstlibxml2(-devel)</li>
</ul></li>
<li><em>I can't install the libxml package, it conflicts with libxml0</em>
<p>You probably have an old libxml0 package used to provide
thesharedlibrary for libxml.so.0, you can probably safely remove it.
Thelibxmlpackages provided on <a href="ftp://xmlsoft.org/libxml2/">xmlsoft.org</a>providelibxml.so.0</p>
</li>
<li><em>I can't install the libxml(2) RPM package due
tofaileddependencies</em>
<p>The most generic solution is to re-fetch the latest src.rpm
,andrebuild it locally with</p>
<p><code>rpm --rebuild libxml(2)-xxx.src.rpm</code>.</p>
<p>If everything goes well it will generate two binary rpm
packages(oneproviding the shared libs and xmllint, and the other one,
the-develpackage, providing includes, static libraries and scripts needed
tobuildapplications with libxml(2)) that you can install locally.</p>
</li>
</ol><h3><a name="Compilatio" id="Compilatio">Compilation</a></h3><ol><li><em>What is the process to compile libxml2 ?</em>
<p>As most UNIX libraries libxml2 follows the "standard":</p>
<p><code>gunzip -c xxx.tar.gz | tar xvf -</code></p>
<p><code>cd libxml-xxxx</code></p>
<p><code>./configure --help</code></p>
<p>to see the options, then the compilation/installation proper</p>
<p><code>./configure [possible options]</code></p>
<p><code>make</code></p>
<p><code>make install</code></p>
<p>At that point you may have to rerun ldconfig or a similar
utilitytoupdate your list of installed shared libs.</p>
</li>
<li><em>What other libraries are needed to compile/install libxml2 ?</em>
<p>Libxml2 does not require any other library, the normal C ANSIAPIshould
be sufficient (please report any violation to this rule youmayfind).</p>
<p>However if found at configuration time libxml2 will detect and
usethefollowing libs:</p>
<ul><li><a href="http://www.info-zip.org/pub/infozip/zlib/">libz</a>:ahighly
portable and available widely compression library.</li>
<li>iconv: a powerful character encoding conversion library.
Itisincluded by default in recent glibc libraries, so it doesn't
needtobe installed specifically on Linux. It now seems a <a href="http://www.opennc.org/onlinepubs/7908799/xsh/iconv.html">partofthe
official UNIX</a>specification. Here is one <a href="http://www.gnu.org/software/libiconv/">implementation
ofthelibrary</a>which source can be found <a href="ftp://ftp.ilog.fr/pub/Users/haible/gnu/">here</a>.</li>
</ul></li>
<li><em>Make check fails on some platforms</em>
<p>Sometimes the regression tests' results don't completely matchthevalue
produced by the parser, and the makefile uses diff to printthedelta. On
some platforms the diff return breaks the compilationprocess;if the diff
is small this is probably not a serious problem.</p>
<p>Sometimes (especially on Solaris) make checks fail due tolimitationsin
make. Try using GNU-make instead.</p>
</li>
<li><em>I use the CVS version and there is no configure script</em>
<p>The configure script (and other Makefiles) are generated.
Usetheautogen.sh script to regenerate the configure script
andMakefiles,like:</p>
<p><code>./autogen.sh --prefix=/usr --disable-shared</code></p>
</li>
<li><em>I have troubles when running make tests with gcc-3.0</em>
<p>It seems the initial release of gcc-3.0 has a problem withtheoptimizer
which miscompiles the URI module. Please useanothercompiler.</p>
</li>
</ol><h3><a name="Developer" id="Developer">Developer</a>corner</h3><ol><li><em>Troubles compiling or linking programs using libxml2</em>
<p>Usually the problem comes from the fact that the compiler
doesn'tgetthe right compilation or linking flags. There is a small
shellscript<code>xml2-config</code>which is installed as part of
libxml2usualinstall process which provides those flags. Use</p>
<p><code>xml2-config --cflags</code></p>
<p>to get the compilation flags and</p>
<p><code>xml2-config --libs</code></p>
<p>to get the linker flags. Usually this is done directly fromtheMakefile
as:</p>
<p><code>CFLAGS=`xml2-config --cflags`</code></p>
<p><code>LIBS=`xml2-config --libs`</code></p>
</li>
<li><em>I want to install my own copy of libxml2 in my home
directoryandlink my programs against it, but it doesn't work</em>
<p>There are many different ways to accomplish this. Here is one waytodo
this under Linux. Suppose your home directory
is<code>/home/user.</code>Then:</p>
<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
subdirectoryin<code>/home/user/myxml</code>, e.g.
<p><code>./configure
--prefix/home/user/myxml/xmlinst</code>{otherconfiguration
options}</p>
</li>
<li>now run <code>make</code>followed by <code>make install</code></li>
<li>At this point, the installation subdirectory contains
thecomplete"private" include files, library files and binary
programfiles (e.g.xmllint), located in
<p><code>/home/user/myxml/xmlinst/lib,/home/user/myxml/xmlinst/include</code>and
<code>/home/user/myxml/xmlinst/bin</code></p>
respectively.</li>
<li>In order to use this "private" library, you should first add
ittothe beginning of your default PATH (so that your own
privateprogramfiles such as xmllint will be used instead of the
normalsystemones). To do this, the Bash command would be
<p><code>export PATH=/home/user/myxml/xmlinst/bin:$PATH</code></p>
</li>
<li>Now suppose you have a program <code>test1.c</code>that
youwouldlike to compile with your "private" library. Simply compile
itusingthe command
<p><code>gcc `xml2-config --cflags --libs` -o test test.c</code></p>
Note that, because your PATH has been set
with<code>/home/user/myxml/xmlinst/bin</code>at the beginning,
thexml2-configprogram which you just installed will be used instead
ofthe systemdefault one, and this will <em>automatically</em>get
thecorrectlibraries linked with your program.</li>
</ul></li>
<p></p>
<li><em>xmlDocDump() generates output on one line.</em>
<p>Libxml2 will not <strong>invent</strong>spaces in the content
ofadocument since <strong>all spaces in the content of a
documentaresignificant</strong>. If you build a tree from the API
andwantindentation:</p>
<ol><li>the correct way is to generate those yourself too.</li>
<li>the dangerous way is to ask libxml2 to add those blanks
toyourcontent <strong>modifying the content of your document
intheprocess</strong>. The result may not be what you expect.
Thereis<strong>NO</strong>way to guarantee that such a
modificationwon'taffect 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:
<p><em>For a XML file as below:</em></p>
<pre><?xml version="1.0"?>
<PLAN xmlns="http://www.argus.ca/autotest/1.0/">
<NODE CommFlag="0"/>
<NODE CommFlag="1"/>
</PLAN></pre>
<p><em>after parsing it with
thefunctionpxmlDoc=xmlParseFile(...);</em></p>
<p><em>I want to the get the content of the first node (node
withtheCommFlag="0")</em></p>
<p><em>so I did it as following;</em></p>
<pre>xmlNodePtr pnode;
pnode=pxmlDoc->children->children;</pre>
<p><em>but it does not work. If I change it to</em></p>
<pre>pnode=pxmlDoc->children->children->next;</pre>
<p><em>then it works. Can someone explain it to me.</em></p>
<p></p>
<p>In XML all characters in the content of the document
aresignificant<strong>including blanks and formatting
linebreaks</strong>.</p>
<p>The extra nodes you are wondering about are just that, text
nodeswiththe formatting spaces which are part of the document but that
peopletendto forget. There is a function <a href="http://xmlsoft.org/html/libxml-parser.html">xmlKeepBlanksDefault()</a>toremove
those at parse time, but that's an heuristic, and itsuse should belimited
to cases where you are certain there is nomixed-content in
thedocument.</p>
</li>
<li><em>I get compilation errors of existing code like
whenaccessing<strong>root</strong>or <strong>child
fields</strong>ofnodes.</em>
<p>You are compiling code developed for libxml version 1 and
usingalibxml2 development environment. Either switch back to libxml v1
develoreven better fix the code to compile with libxml2 (or both) by <a href="upgrade.html">following the instructions</a>.</p>
</li>
<li><em>I get compilation errors about
nonexisting<strong>xmlRootNode</strong>or<strong>xmlChildrenNode</strong>fields.</em>
<p>The source code you are using has been <a href="upgrade.html">upgraded</a>to be able to compile with both
libxmlandlibxml2, but you need to install a more recent
version:libxml(-devel)>= 1.8.8 or libxml2(-devel) >= 2.1.0</p>
</li>
<li><em>XPath implementation looks seriously broken</em>
<p>XPath implementation prior to 2.3.0 was really incomplete. Upgrade
toarecent version, there are no known bugs in the current version.</p>
</li>
<li><em>The example provided in the web page does not compile.</em>
<p>It's hard to maintain the documentation in sync with
thecode<grin/> ...</p>
<p>Check the previous points 1/ and 2/ raised before, and
pleasesendpatches.</p>
</li>
<li><em>Where can I get more examples and information than provided
ontheweb page?</em>
<p>Ideally a libxml2 book would be nice. I have no such plan ...
Butyoucan:</p>
<ul><li>check more deeply the <a href="html/libxml-lib.html">existinggenerated doc</a></li>
<li>have a look at <a href="examples/index.html">the
setofexamples</a>.</li>
<li>look for examples of use for libxml2 function using the
Gnomecode.For example the following will query the full Gnome CVS
base fortheuse of the <strong>xmlAddChild()</strong>function:
<p><a href="http://cvs.gnome.org/lxr/search?string=xmlAddChild">http://cvs.gnome.org/lxr/search?string=xmlAddChild</a></p>
<p>This may be slow, a large hardware donation to the
gnomeprojectcould cure this :-)</p>
</li>
<li><a href="http://cvs.gnome.org/bonsai/rview.cgi?cvsroot=/cvs/gnome&dir=gnome-xml">Browsethelibxml2
source</a>, I try to write code as clean and documentedaspossible, so
looking at it may be helpful. In particular the codeofxmllint.c and
of the various testXXX.c test programs shouldprovidegood examples of
how to do things with the library.</li>
</ul></li>
<li>What about C++ ?
<p>libxml2 is written in pure C in order to allow easy reuse on anumberof
platforms, including embedded systems. I don't intend to converttoC++.</p>
<p>There is however a C++ wrapper which may fulfill your needs:</p>
<ul><li>by Ari Johnson <ari@btigate.com>:
<p>Website: <a href="http://libxmlplusplus.sourceforge.net/">http://libxmlplusplus.sourceforge.net/</a></p>
<p>Download: <a href="http://sourceforge.net/project/showfiles.php?group_id=12999">http://sourceforge.net/project/showfiles.php?group_id=12999</a></p>
</li>
<!-- Website is currently unavailable as of 2003-08-02
<li>by Peter Jones <pjones@pmade.org>
<p>Website: <a
href="http://pmade.org/pjones/software/xmlwrapp/">http://pmade.org/pjones/software/xmlwrapp/</a></p>
</li>
-->
</ul></li>
<li>How to validate a document a posteriori ?
<p>It is possible to validate documents which had not been
validatedatinitial parsing time or documents which have been built
fromscratchusing 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 existingdocument:</p>
<pre>xmlDocPtr doc; /* your existing document */
xmlDtdPtr dtd = xmlParseDTD(NULL, filename_of_dtd); /* parse the DTD */
dtd->name = xmlStrDup((xmlChar*)"root_name"); /* use the given root */
doc->intSubset = dtd;
if (doc->children == NULL) xmlAddChild((xmlNodePtr)doc, (xmlNodePtr)dtd);
else xmlAddPrevSibling(doc->children, (xmlNodePtr)dtd);
</pre>
</li>
<li>So what is this funky "xmlChar" used all the time?
<p>It is a null terminated sequence of utf-8 characters. And
onlyutf-8!You need to convert strings encoded in different ways to
utf-8beforepassing them to the API. This can be accomplished with the
iconvlibraryfor instance.</p>
</li>
<li>etc ...</li>
</ol><p></p><p><a href="bugs.html">Daniel Veillard</a></p></td></tr></table></td></tr></table></td></tr></table></td></tr></table></td></tr></table></body></html>
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