FAQ.html revision 142fb21c10a61180422a51158683f3034268e7b9
1<?xml version="1.0" encoding="ISO-8859-1"?> 2<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> 3<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1" /><link rel="SHORTCUT ICON" href="/favicon.ico" /><style type="text/css"> 4TD {font-family: Verdana,Arial,Helvetica} 5BODY {font-family: Verdana,Arial,Helvetica; margin-top: 2em; margin-left: 0em; margin-right: 0em} 6H1 {font-family: Verdana,Arial,Helvetica} 7H2 {font-family: Verdana,Arial,Helvetica} 8H3 {font-family: Verdana,Arial,Helvetica} 9A:link, A:visited, A:active { text-decoration: underline } 10</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="http://xmlsoft.org/wiki">Wiki</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.zveno.com/open_source/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://rubyforge.org/projects/xml-tools/">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> 11 <li><a href="FAQ.html#Installati">Installation</a></li> 12 <li><a href="FAQ.html#Compilatio">Compilation</a></li> 13 <li><a href="FAQ.html#Developer">Developer corner</a></li> 14</ul><h3><a name="License" id="License">License</a>(s)</h3><ol><li><em>Licensing Terms for libxml</em> 15 <p>libxml2 is released under the <a href="http://www.opensource.org/licenses/mit-license.html">MIT 16 License</a>; see the file Copyright in the distribution for the precise 17 wording</p> 18 </li> 19 <li><em>Can I embed libxml2 in a proprietary application ?</em> 20 <p>Yes. The MIT License allows you to keep proprietary the changes you 21 made to libxml, but it would be graceful to send-back bug fixes and 22 improvements as patches for possible incorporation in the main 23 development tree.</p> 24 </li> 25</ol><h3><a name="Installati" id="Installati">Installation</a></h3><ol><li><strong><span style="background-color: #FF0000">Do Not Use 26 libxml1</span></strong>, use libxml2</li> 27 <li><em>Where can I get libxml</em> ? 28 <p>The original distribution comes from <a href="ftp://rpmfind.net/pub/libxml/">rpmfind.net</a> or <a href="ftp://ftp.gnome.org/pub/GNOME/sources/libxml2/2.6/">gnome.org</a></p> 29 <p>Most Linux and BSD distributions include libxml, this is probably the 30 safer way for end-users to use libxml.</p> 31 <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> 32 </li> 33 <li><em>I see libxml and libxml2 releases, which one should I install ?</em> 34 <ul><li>If you are not constrained by backward compatibility issues with 35 existing applications, install libxml2 only</li> 36 <li>If you are not doing development, you can safely install both. 37 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 38 compatible (this is not the case for development packages).</li> 39 <li>If you are a developer and your system provides separate packaging 40 for shared libraries and the development components, it is possible 41 to install libxml and libxml2, and also <a href="http://rpmfind.net/linux/RPM/libxml-devel.html">libxml-devel</a> 42 and <a href="http://rpmfind.net/linux/RPM/libxml2-devel.html">libxml2-devel</a> 43 too for libxml2 >= 2.3.0</li> 44 <li>If you are developing a new application, please develop against 45 libxml2(-devel)</li> 46 </ul></li> 47 <li><em>I can't install the libxml package, it conflicts with libxml0</em> 48 <p>You probably have an old libxml0 package used to provide the shared 49 library for libxml.so.0, you can probably safely remove it. The libxml 50 packages provided on <a href="ftp://rpmfind.net/pub/libxml/">rpmfind.net</a> provide 51 libxml.so.0</p> 52 </li> 53 <li><em>I can't install the libxml(2) RPM package due to failed 54 dependencies</em> 55 <p>The most generic solution is to re-fetch the latest src.rpm , and 56 rebuild it locally with</p> 57 <p><code>rpm --rebuild libxml(2)-xxx.src.rpm</code>.</p> 58 <p>If everything goes well it will generate two binary rpm packages (one 59 providing the shared libs and xmllint, and the other one, the -devel 60 package, providing includes, static libraries and scripts needed to build 61 applications with libxml(2)) that you can install locally.</p> 62 </li> 63</ol><h3><a name="Compilatio" id="Compilatio">Compilation</a></h3><ol><li><em>What is the process to compile libxml2 ?</em> 64 <p>As most UNIX libraries libxml2 follows the "standard":</p> 65 <p><code>gunzip -c xxx.tar.gz | tar xvf -</code></p> 66 <p><code>cd libxml-xxxx</code></p> 67 <p><code>/configure --help</code></p> 68 <p>to see the options, then the compilation/installation proper</p> 69 <p><code>/configure [possible options]</code></p> 70 <p><code>make</code></p> 71 <p><code>make install</code></p> 72 <p>At that point you may have to rerun ldconfig or a similar utility to 73 update your list of installed shared libs.</p> 74 </li> 75 <li><em>What other libraries are needed to compile/install libxml2 ?</em> 76 <p>Libxml2 does not require any other library, the normal C ANSI API 77 should be sufficient (please report any violation to this rule you may 78 find).</p> 79 <p>However if found at configuration time libxml2 will detect and use the 80 following libs:</p> 81 <ul><li><a href="http://www.info-zip.org/pub/infozip/zlib/">libz</a> : a 82 highly portable and available widely compression library.</li> 83 <li>iconv: a powerful character encoding conversion library. It is 84 included by default in recent glibc libraries, so it doesn't need to 85 be installed specifically on Linux. It now seems a <a href="http://www.opennc.org/onlinepubs/7908799/xsh/iconv.html">part 86 of the official UNIX</a> specification. Here is one <a href="http://www.gnu.org/software/libiconv/">implementation of the 87 library</a> which source can be found <a href="ftp://ftp.ilog.fr/pub/Users/haible/gnu/">here</a>.</li> 88 </ul></li> 89 <li><em>Make check fails on some platforms</em> 90 <p>Sometimes the regression tests' results don't completely match the 91 value produced by the parser, and the makefile uses diff to print the 92 delta. On some platforms the diff return breaks the compilation process; 93 if the diff is small this is probably not a serious problem.</p> 94 <p>Sometimes (especially on Solaris) make checks fail due to limitations 95 in make. Try using GNU-make instead.</p> 96 </li> 97 <li><em>I use the CVS version and there is no configure script</em> 98 <p>The configure script (and other Makefiles) are generated. Use the 99 autogen.sh script to regenerate the configure script and Makefiles, 100 like:</p> 101 <p><code>/autogen.sh --prefix=/usr --disable-shared</code></p> 102 </li> 103 <li><em>I have troubles when running make tests with gcc-3.0</em> 104 <p>It seems the initial release of gcc-3.0 has a problem with the 105 optimizer which miscompiles the URI module. Please use another 106 compiler.</p> 107 </li> 108</ol><h3><a name="Developer" id="Developer">Developer</a> corner</h3><ol><li><em>Troubles compiling or linking programs using libxml2</em> 109 <p>Usually the problem comes from the fact that the compiler doesn't get 110 the right compilation or linking flags. There is a small shell script 111 <code>xml2-config</code> which is installed as part of libxml2 usual 112 install process which provides those flags. Use</p> 113 <p><code>xml2-config --cflags</code></p> 114 <p>to get the compilation flags and</p> 115 <p><code>xml2-config --libs</code></p> 116 <p>to get the linker flags. Usually this is done directly from the 117 Makefile as:</p> 118 <p><code>CFLAGS=`xml2-config --cflags`</code></p> 119 <p><code>LIBS=`xml2-config --libs`</code></p> 120 </li> 121 <li><em>I want to install my own copy of libxml2 in my home directory and link 122 my programs against it, but it doesn't work</em> 123 <p>There are many different ways to accomplish this. Here is one way to 124 do this under Linux. Suppose your home directory is <code>/home/user. 125 </code>Then:</p> 126 <ul><li>Create a subdirectory, let's call it <code>myxml</code></li> 127 <li>unpack the libxml2 distribution into that subdirectory</li> 128 <li>chdir into the unpacked distribution (<code>/home/user/myxml/libxml2 129 </code>)</li> 130 <li>configure the library using the "<code>--prefix</code>" switch, 131 specifying an installation subdirectory in <code>/home/user/myxml</code>, 132 e.g. 133 <p><code>/configure --prefix /home/user/myxml/xmlinst</code> {other 134 configuration options}</p></li> 135 <li>now run <code>make</code> followed by <code>make install</code></li> 136 <li>At this point, the installation subdirectory contains the complete 137 "private" include files, library files and binary program files (e.g. 138 xmllint), located in 139 <p> <code>/home/user/myxml/xmlinst/lib, /home/user/myxml/xmlinst/include 140 </code> and <code> /home/user/myxml/xmlinst/bin</code></p> 141 respectively.</li> 142 <li>In order to use this "private" library, you should first add it 143 to the beginning of your default PATH (so that your own private 144 program files such as xmllint will be used instead of the normal 145 system ones). To do this, the Bash command would be 146 <p><code>export PATH=/home/user/myxml/xmlinst/bin:$PATH</code></p></li> 147 <li>Now suppose you have a program <code>test1.c</code> that you would 148 like to compile with your "private" library. Simply compile it 149 using the command <p><code>gcc `xml2-config --cflags --libs` -o test 150 test.c</code></p> Note that, because your PATH has been set with <code> 151 /home/user/myxml/xmlinst/bin</code> at the beginning, the 152 xml2-config program which you just installed will be used instead of 153 the system default one, and this will <em>automatically</em> get the 154 correct libraries linked with your program.</li></ul></li><p></p> 155 <li><em>xmlDocDump() generates output on one line.</em> 156 <p>Libxml2 will not <strong>invent</strong> spaces in the content of a 157 document since <strong>all spaces in the content of a document are 158 significant</strong>. If you build a tree from the API and want 159 indentation:</p> 160 <ol><li>the correct way is to generate those yourself too.</li> 161 <li>the dangerous way is to ask libxml2 to add those blanks to your 162 content <strong>modifying the content of your document in the 163 process</strong>. The result may not be what you expect. There is 164 <strong>NO</strong> way to guarantee that such a modification won't 165 affect other parts of the content of your document. See <a href="http://xmlsoft.org/html/libxml-parser.html#xmlKeepBlanksDefault">xmlKeepBlanksDefault 166 ()</a> and <a href="http://xmlsoft.org/html/libxml-tree.html#xmlSaveFormatFile">xmlSaveFormatFile 167 ()</a></li> 168 </ol></li> 169 <li>Extra nodes in the document: 170 <p><em>For a XML file as below:</em></p> 171 <pre><?xml version="1.0"?> 172<PLAN xmlns="http://www.argus.ca/autotest/1.0/"> 173<NODE CommFlag="0"/> 174<NODE CommFlag="1"/> 175</PLAN></pre> 176 <p><em>after parsing it with the function 177 pxmlDoc=xmlParseFile(...);</em></p> 178 <p><em>I want to the get the content of the first node (node with the 179 CommFlag="0")</em></p> 180 <p><em>so I did it as following;</em></p> 181 <pre>xmlNodePtr pnode; 182pnode=pxmlDoc->children->children;</pre> 183 <p><em>but it does not work. If I change it to</em></p> 184 <pre>pnode=pxmlDoc->children->children->next;</pre> 185 <p><em>then it works. Can someone explain it to me.</em></p> 186 <p></p> 187 <p>In XML all characters in the content of the document are significant 188 <strong>including blanks and formatting line breaks</strong>.</p> 189 <p>The extra nodes you are wondering about are just that, text nodes with 190 the formatting spaces which are part of the document but that people tend 191 to forget. There is a function <a href="http://xmlsoft.org/html/libxml-parser.html">xmlKeepBlanksDefault 192 ()</a> to remove those at parse time, but that's an heuristic, and its 193 use should be limited to cases where you are certain there is no 194 mixed-content in the document.</p> 195 </li> 196 <li><em>I get compilation errors of existing code like when accessing 197 <strong>root</strong> or <strong>child fields</strong> of nodes.</em> 198 <p>You are compiling code developed for libxml version 1 and using a 199 libxml2 development environment. Either switch back to libxml v1 devel or 200 even better fix the code to compile with libxml2 (or both) by <a href="upgrade.html">following the instructions</a>.</p> 201 </li> 202 <li><em>I get compilation errors about non existing 203 <strong>xmlRootNode</strong> or <strong>xmlChildrenNode</strong> 204 fields.</em> 205 <p>The source code you are using has been <a href="upgrade.html">upgraded</a> to be able to compile with both libxml 206 and libxml2, but you need to install a more recent version: 207 libxml(-devel) >= 1.8.8 or libxml2(-devel) >= 2.1.0</p> 208 </li> 209 <li><em>XPath implementation looks seriously broken</em> 210 <p>XPath implementation prior to 2.3.0 was really incomplete. Upgrade to 211 a recent version, there are no known bugs in the current version.</p> 212 </li> 213 <li><em>The example provided in the web page does not compile.</em> 214 <p>It's hard to maintain the documentation in sync with the code 215 <grin/> ...</p> 216 <p>Check the previous points 1/ and 2/ raised before, and please send 217 patches.</p> 218 </li> 219 <li><em>Where can I get more examples and information than provided on the 220 web page?</em> 221 <p>Ideally a libxml2 book would be nice. I have no such plan ... But you 222 can:</p> 223 <ul><li>check more deeply the <a href="html/libxml-lib.html">existing 224 generated doc</a></li> 225 <li>have a look at <a href="examples/index.html">the set of 226 examples</a>.</li> 227 <li>look for examples of use for libxml2 function using the Gnome code. 228 For example the following will query the full Gnome CVS base for the 229 use of the <strong>xmlAddChild()</strong> function: 230 <p><a href="http://cvs.gnome.org/lxr/search?string=xmlAddChild">http://cvs.gnome.org/lxr/search?string=xmlAddChild</a></p> 231 <p>This may be slow, a large hardware donation to the gnome project 232 could cure this :-)</p> 233 </li> 234 <li><a href="http://cvs.gnome.org/bonsai/rview.cgi?cvsroot=/cvs/gnome&dir=gnome-xml">Browse 235 the libxml2 source</a> , I try to write code as clean and documented 236 as possible, so looking at it may be helpful. In particular the code 237 of xmllint.c and of the various testXXX.c test programs should 238 provide good examples of how to do things with the library.</li> 239 </ul></li> 240 <li>What about C++ ? 241 <p>libxml2 is written in pure C in order to allow easy reuse on a number 242 of platforms, including embedded systems. I don't intend to convert to 243 C++.</p> 244 <p>There is however a C++ wrapper which may fulfill your needs:</p> 245 <ul><li>by Ari Johnson <ari@btigate.com>: 246 <p>Website: <a href="http://libxmlplusplus.sourceforge.net/">http://libxmlplusplus.sourceforge.net/</a></p> 247 <p>Download: <a href="http://sourceforge.net/project/showfiles.php?group_id=12999">http://sourceforge.net/project/showfiles.php?group_id=12999</a></p> 248 </li> 249 <!-- Website is currently unavailable as of 2003-08-02 250 <li>by Peter Jones <pjones@pmade.org> 251 <p>Website: <a 252 href="http://pmade.org/pjones/software/xmlwrapp/">http://pmade.org/pjones/software/xmlwrapp/</a></p> 253 </li> 254 --> 255 </ul></li> 256 <li>How to validate a document a posteriori ? 257 <p>It is possible to validate documents which had not been validated at 258 initial parsing time or documents which have been built from scratch 259 using the API. Use the <a href="http://xmlsoft.org/html/libxml-valid.html#xmlValidateDtd">xmlValidateDtd()</a> 260 function. It is also possible to simply add a DTD to an existing 261 document:</p> 262 <pre>xmlDocPtr doc; /* your existing document */ 263xmlDtdPtr dtd = xmlParseDTD(NULL, filename_of_dtd); /* parse the DTD */ 264 265 dtd->name = xmlStrDup((xmlChar*)"root_name"); /* use the given root */ 266 267 doc->intSubset = dtd; 268 if (doc->children == NULL) xmlAddChild((xmlNodePtr)doc, (xmlNodePtr)dtd); 269 else xmlAddPrevSibling(doc->children, (xmlNodePtr)dtd); 270 </pre> 271 </li> 272 <li>So what is this funky "xmlChar" used all the time? 273 <p>It is a null terminated sequence of utf-8 characters. And only utf-8! 274 You need to convert strings encoded in different ways to utf-8 before 275 passing them to the API. This can be accomplished with the iconv library 276 for instance.</p> 277 </li> 278 <li>etc ...</li> 279</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> 280
