<!DOCTYPE html PUBLIC “-//W3C//DTD XHTML 1.0 Transitional//EN” “www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd”> <html xmlns=“www.w3.org/1999/xhtml”> http-equiv=“Content-Type” content=“text/html; charset=UTF-8” /><link rel=“SHORTCUT ICON” href=“/favicon.ico” /><style type=“text/css”> TD {font-family: Verdana,Arial,Helvetica} BODY {font-family: Verdana,Arial,Helvetica; margin-top: 2em; margin-left: 0em; margin-right: 0em} H1 {font-family: Verdana,Arial,Helvetica} H2 {font-family: Verdana,Arial,Helvetica} H3 {font-family: Verdana,Arial,Helvetica} A:link, A:visited, A:active { text-decoration: underline } </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=“swpat.ffii.org/”> src=“epatents.png” alt=“Action against software patents” /></a></td><td width=“180”><a href=“www.gnome.org/”> src=“gnome2.png” alt=“Gnome2 Logo” /></a><a href=“www.w3.org/Status”> src=“w3c.png” alt=“W3C Logo” /></a><a href=“www.redhat.com/”> src=“redhat.gif” alt=“Red Hat Logo” /></a><div align=“left”><a href=“xmlsoft.org/”> 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=“Mail”>mail.gnome.org/archives/xml/“>Mail archive</a></li><li><a href=”XSLT“>xmlsoft.org/XSLT/”>XSLT libxslt</a></li><li><a href=“DOM”>phd.cs.unibo.it/gdome2/“>DOM gdome2</a></li><li><a href=”XML-DSig“>www.aleksey.com/xmlsec/”>XML-DSig xmlsec</a></li><li><a href=“FTP

  • xmlsoft.org/”>FTP
  • href=“Windows”>www.zlatkovic.com/projects/libxml/“>Windows binaries</a></li><li><a href=”Solaris“>opencsw.org/packages/libxml2”>Solaris binaries</a></li><li><a href=“MacOsX”>www.explain.com.au/oss/libxml2xslt.html“>MacOsX binaries</a></li><li><a href=”lxml“>lxml.de/”>lxml Python bindings</a></li><li><a href=“Perl”>cpan.uwinnipeg.ca/dist/XML-LibXML“>Perl bindings</a></li><li><a href=”C“>libxmlplusplus.sourceforge.net/”>C++ bindings</a></li><li><a href=“PHP”>www.zend.com/php5/articles/php5-xmlphp.php#Heading4“>PHP bindings</a></li><li><a href=”Pascal“>sourceforge.net/projects/libxml2-pas/”>Pascal bindings</a></li><li><a href=“Ruby”>libxml.rubyforge.org/“>Ruby bindings</a></li><li><a href=”Tcl“>tclxml.sourceforge.net/”>Tcl bindings</a></li><li><a href=“Bug”>gitlab.gnome.org/GNOME/libxml2/issues“>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">MIT
      License</a>; see the file Copyright in the distribution for the precise
      wording</p>
    </li>
    <li><em>Can I embed libxml2 in a proprietary application ?</em>
      <p>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.</p>
    </li>

    </ol><h3><a name=“Installati” id=“Installati”>Installation</a></h3><ol>

    <li><strong><span style="background-color: #FF0000">Do Not Use
      libxml1</span></strong>, use libxml2</li>
    <p></p>
    <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 probably the
      safer 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>
    <p></p>
    <li><em>I see libxml and libxml2 releases, which one should I install ?</em>
      <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><em>I can't install the libxml package, it conflicts with libxml0</em>
      <p>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</p>
    </li>
    <li><em>I can't install the libxml(2) RPM package due to failed
      dependencies</em>
      <p>The most generic solution is to re-fetch the latest src.rpm , and
      rebuild 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 (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.</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 utility to
      update 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 ANSI API
      should be sufficient (please report any violation to this rule you may
      find).</p>
      <p>However if found at configuration time libxml2 will detect and use the
      following libs:</p>
      <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>
    <p></p>
    <li><em>Make check fails on some platforms</em>
      <p>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.</p>
      <p>Sometimes (especially on Solaris) make checks fail due to limitations
      in make. Try using GNU-make instead.</p>
    </li>
    <li><em>I use the SVN version and there is no configure script</em>
      <p>The configure script (and other Makefiles) are generated. Use the
      autogen.sh script to regenerate the configure script and Makefiles,
      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 with the
      optimizer which miscompiles the URI module. Please use another
      compiler.</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'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</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 from the
      Makefile 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 directory and
      link my programs against it, but it doesn't work</em>
      <p>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:</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 subdirectory in
          <code>/home/user/myxml</code>, e.g.
          <p><code>./configure --prefix /home/user/myxml/xmlinst</code> {other
          configuration options}</p>
        </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
          <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 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
          <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 you would
          like to compile with your "private" library.  Simply compile it using
          the 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, the xml2-config
          program which you just installed will be used instead of the system
          default one, and this will <em>automatically</em> get the correct
          libraries 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 of a
      document since <strong>all spaces in the content of a document are
      significant</strong>. If you build a tree from the API and want
      indentation:</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 to your
          content <strong>modifying the content of your document in the
          process</strong>. The result may not be what you expect. There is
          <strong>NO</strong> 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>
    <p></p>
    <li><em>Extra nodes in the document:</em>
      <p><em>For an XML file as below:</em></p>
      <pre>&lt;?xml version="1.0"?&gt;

    &lt;PLAN xmlns=“www.argus.ca/autotest/1.0/”>; &lt;NODE CommFlag=“0”/&gt; &lt;NODE CommFlag=“1”/&gt; &lt;/PLAN&gt;</pre>

    <p><em>after parsing it with the function
    pxmlDoc=xmlParseFile(...);</em></p>
    <p><em>I want to the get the content of the first node (node with the
    CommFlag="0")</em></p>
    <p><em>so I did it as following;</em></p>
    <pre>xmlNodePtr pnode;

    pnode=pxmlDoc-&gt;children-&gt;children;</pre>

      <p><em>but it does not work. If I change it to</em></p>
      <pre>pnode=pxmlDoc-&gt;children-&gt;children-&gt;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 are significant
      <strong>including blanks and formatting line breaks</strong>.</p>
      <p>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.</p>
    </li>
    <li><em>I get compilation errors of existing code like when accessing
      <strong>root</strong> or <strong>child fields</strong> of nodes.</em>
      <p>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>.</p>
    </li>
    <li><em>I get compilation errors about non existing
      <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 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</p>
    </li>
    <li><em>Random crashes in threaded applications</em>
      <p>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.</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 the code
      &lt;grin/&gt; ...</p>
      <p>Check the previous points 1/ and 2/ raised before, and please send
      patches.</p>
    </li>
    <li><em>Where can I get more examples and information than provided on the
      web page?</em>
      <p>Ideally a libxml2 book would be nice. I have no such plan ... But you
      can:</p>
      <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>
    <p></p>
    <li><em>What about C++ ?</em>
      <p>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++.</p>
      <p>There is however a C++ wrapper which may fulfill your needs:</p>
      <ul>
        <li>by Ari Johnson &lt;ari@btigate.com&gt;:
          <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>
      </ul>
    </li>
    <li><em>How to validate a document a posteriori ?</em>
      <p>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:</p>
      <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><em>So what is this funky "xmlChar" used all the time?</em>
      <p>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.</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>