tDOM is a Tcl extension for parsing XML.


Rolf Ade has said that the most valuable thing in tDOM is Jochen Loewer's implementation of xpath, which is written in C.

PT: I'll second that. tDOM's XPath processing is extremely competent.


Based on the Expat parser
allows access to the DOM trees as Tcl DOM objects
Includes an HTML reader that reads HTML and generates a DOM tree.
Includes novel mechanisms such as appendFromScript for generating elements.

See Also

Interfacing with XML
which combines tDOM and BWidget - Playing SAX.
Natively accessing XML and Tcllib tree style interface to tDOM
which modify/extend the tDOM API
XML Graph to canvas
uses expat and Tcldot to render directed graphs
XML/tDOM encoding issues with the http package
tDOM and Coroutines
using coroutines with tDOM and Expat to parse a document in SAX mode


Create an in-memory DOM tree from XML
Manipulates an instance of a DOM document object
Manipulates an instance of a DOM node object
Creates an instance of an expat parser object
Functions to create, install and remove expat parser object extensions.
tdom is an expat parser object extension to create an in-memory DOM tree from the input while parsing.
tnc is an expat parser object extension, that validates the XML stream against the document DTD while parsing.

Tutorials and articles

A tDOM tutorial
available here on the Wiki.
tDOM – A fast XML/DOM/XPath package for Tcl written in C (alternate )
by Jochen Loewer, a valuable description of tDOM's origins and uses presented at the first European Tcl Conference.
tclum2001-tdom.pdf (alternates (compressed) 1 2 ), Jochen Loewer, Second European Tcl/Tk Users Meeting, 2001
design, API, usage, eBay web scraping example
Processing XML documents with Tcl and tDOM
Carsten Zerbst, 2003, illustrating how practical and easy tDOM is. And here's the same article in german: XML-Dokumente mit Tcl und tDOM bearbeiten
XMI and UML combine to drive product development , Cameron Laird, 2001
profiles a company (Ideogramic) that uses tDOM for XMI processing in its product.
Using tDOM and tDOM XSLT , Cameron Laird, 2002-02-01
highlights tDOM's performance, while also supplying a recipe for your own start with the package.


tDOM-0.9.2, 26. Aug. 2020:


official repository , maintained by Rolf Ade
To clone with fossil:
fossil clone
irrational-numbers project
A collection of binaries for Win/Linux/Mac in a single package. At runtime the right binary library is selected. Aligned with tdom 0.9.2
Jochem Huhmann: A binary package of tDOM 0.7.4 for Debian

GNU/Linux 3.0 (Woody)

the Yahoo tdom group
Various combinations of mirrors, backups, and experimental work are often

announced here. This is particularly important, as seems relatively erratic in reliability. The authors of tdom announce their new releases here.

provided by Phaseit


issue tracker
yahoo tdom group


RS 2011-02-28:

Since my employer applies stricter license checks now, I was told that I cannot use tdom in software for customers any more, because of a license conflict:

  • The library itself is under MPL (Mozilla Public License)
  • Two of the source files are under LGPL: generic/DOMhtml.c and generic/XMLsimple.c

According to the FSF, these two licenses are contradicting. Can this be helped?

schlenk 2011-02-28: Those two LGPL headers seem to be from drh probably taken from tkhtml2? If yes it should be easy enough to fix, as DRH has release the tkhtml2 code into public domain and tkhtml3 is BSD licensed (was LGPL before). Probably just needs asking drh and Rolf Ade to fix it.

HaO 2022-12-05: I have checked the files mentioned by RS in tdom 0.9.2. They now have a MPL 2.0 licence. So, the issue is gone. They still state, that this is pre-alpha quality ;-).

Also note, that TDOM has changed the MPL licence version from 1.1 to 2.0 with TDOM 0.9.2.

To fullfill the obligations of the licence, when using the software, one should:

  • Distribute all 3 licence files of the source distribution LICENCE, MPL_2.0.html, expat/COPYING.
  • Give the source code location, e.g. [L1 ]


Downloading your utility usage from Pacific Gas and Electric using TCL

A tDOM tutorial could include these points (proposed by Rolf Ade):

  • how to use the SAX interface (setting up event handler scripts, stacking event handler scripts, error handling etc)
  • how to parse (parse a string, or read the XML data out of a channel, with notes about the encoding problems)
  • how to get a DOM tree representation of XML data
  • the XPointer, DOM 1 and DOM 2 and XPath commands to find or to navigate to some nodes of interest
  • how to use tDOM's XSLT engine (to build an XSLT processor or in server application)
  • how to serialize DOM trees (as XML, HTML or text)
  • how to validate the XML data while parsing
  • how to create DOM trees from scratch
  • how to create additional, tcl scripted DOM methods
  • how to create additional, tcl scripted XPath functions

Example: An XPath query

PS 2004-11-04:

A quick way to get values from XML documents:

set xml {
    <agent id="007">
        <name type="first">James</name>
        <name type="last">Bond</name>
        <age>Still attractive</age>
    <agent id="013">
        <name type="first">Austin</name>
        <name type="last">Powers</name>
        <age>Depends on your timeline</age>
        <sex>Yes, please</sex>

set dom [dom parse $xml]
set doc [$dom documentElement]
puts "Agent: [$doc selectNodes {string(/agents/agent[@id='013']/@id)}]"
puts "First Name: [$doc selectNodes {string(/agents/agent[@id='013']/name[@type='first'])}]"
puts "Last Name: [$doc selectNodes {string(/agents/agent[@id='013']/name[@type='last'])}]"
puts "Age: [$doc selectNodes {string(/agents/agent[@id='013']/age)}]"

Will output:

Agent: 013
First Name: Austin
Last Name: Powers
Age: Depends on your timeline

Example: innerXML as extension to the DOM node methods

heinrichmartin: 2014-06-05

  • initial version

heinrichmartin: 2015-03-26

  • re-use parameter checks from asXML (allows -indentAttrs from trunk)
  • fixed indentation of first line

proc comment in TclDoc format:

% package require tdom
%    # returns the inner XML of a node
   # @param node a DOM node
   # @param -indent the optional indentation (see tdom's <code>asXML -indent</code>). Defaults to use tdom's default
   # @param -indentAttrs the optional attribute indentation (see tdom's <code>asXML -indentAttrs</code>). Defaults to use tdom's default
   # @return the inner XML string
   proc ::dom::domNode::innerXML {node args} {
      # re-use parameter checks from asXML
      set result [$node asXML {*}$args]
      if {[$node hasChildNodes]} {
         # strip element tag
         set result [string replace $result 0 [string first ">" $result]]
         set result [string replace $result [string last "<" $result] end]
         # strip whitespace, but not the indentation
         set indent ""
         regexp {^\s*?\n??([ \t]*?)\S} $result -> indent
         set result $indent[string trim $result]
         return $result
      } else {
         return [$node text]
% % % % % %
% dom parse {<A specialchar="&lt;"><B><C x="y"/></B></A>} doc
% $doc documentElement root
% [$root selectNodes //C] innerXML
% [$root selectNodes //B] innerXML
    <C x="y"/>
% [$root selectNodes //A] innerXML
        <C x="y"/>
% [$root selectNodes //A] innerXML -indent none
<B><C x="y"/></B>
% [$root selectNodes //A] innerXML -indent 0
<C x="y"/>

XML Namespaces

PYK 2019-08-16:

Commands such as createElement and appendFromList are not XML-namespace-aware. They can be used to generate documents with elements that have namespaced tags and attributes, but those tags and attributes aren't bound to a namespace. This is sufficient if the goal is simply to generate a well-formed XML document containing expanded names .

tdomutil , provides an pure-Tcl implementation of appendFromList that uses the intended parent node and its ancestors to resolve the namespace for a given prefix.

An XPath query with a namespace

Trying to retrieve elements from a namespace was confusing me until I found Making XPATH queries against a document w/ namespaces , comp.lang.tcl, 2006-04-27, which demonstrates the use of -namespaces with selectNodes.

skm 2006-12-10

% set fh [open small.gpx]
% set xmldata [read $fh]
<?xml version="1.0"?>
creator="ExpertGPS 1.1 -"
<bounds minlat="42.401051" minlon="-71.126602" maxlat="42.468655" maxlon="-71.102973"/>
<wpt lat="42.438878" lon="-71.119277">
<wpt lat="42.439227" lon="-71.119689">

% close $fh

This is edited down from for brevity's sake.

Get the doc and the root.

% set doc [dom parse $xmldata]
% set root [$doc documentElement]

Try to get a list of waypoints

Define a namespace and use it with selectNodes

% set ns {gpxns}

Sample XPath queries with and without the namespace

% $root selectNodes -namespaces $ns //wpt
% $root selectNodes -namespaces $ns //gpxns:wpt
domNode013B2060 domNode013B2194
% $root selectNodes -namespaces $ns {//gpxns:wpt[1]}

kpv Another approach is to set the namespaces to be searched once in the beginning.

% $doc selectNodesNamespaces $ns
% $root selectNodes gpxns:wpt

Example: Parse HTML

Using tdom to parse some html:

package require tdom
package require http

# html - the source of the html page
proc pullOutTheURLs {html} {

# Parse your HTML document into a DOM tree structure
set doc [dom parse -html $html]

# root will be the root element of your HTML document,
# ie. the HTML element
set root [$doc documentElement]

# The following finds all anchor links <a>. It isn't clear to me,
# if you also interested in the urls of <area>, <link> and <base>
# elements.
set nodeList [$root selectNodes {descendant::a}]

# init the result list
set urlList {}

# Pull out the Values of the href attributes
foreach node $nodeList {
    set attList [$node attributes *]
    foreach attribute $attList {
        if {[string tolower $attribute] == "href"} {
            lappend urlList [$node getAttribute $attribute]

# Get rid of the DOM representation of your HTML document
$doc delete

# finished
return $urlList

# Test it
set urlList [pullOutTheURLs [http::data [http::geturl [lindex $argv 0]]]]

foreach url $urlList {
    puts $url

MHN 2012-11-08: I have not tested the performance, but the nested foreach looks like an overhead (compared to byte-code tdom)... How about the following?

# pull out the values of the href attributes
foreach attr [$root selectNodes {descendant::a/@href}] {
    lappend urlList [lindex $attr 1]

# if case insensitive matching is required, use {descendant::a/@*['href' = translate(name(),'HREF','href')]}

# if no URL matches "href" then it can be achieved in one line
set urlList [lsearch -all -inline -exact -not [concat {*}[$root selectNodes descendant::a/@href]] href]

XSLT Example

I am an XSLT newbie. I didn't find an XSLT example for tDOM on the wiki, so I thought I would provide one. It is almost too easy to warrant one, but I think it helps anyway.

I took the sample XML and simple XSL from What kind of language is XSLT? , Michael Kay, 2005-04-20. For paste here, I will use a shorter version of the xml file.

% package require tdom
% set gamedata {<results group="A">
    <team score="2">Brazil</team>
    <team score="1">Scotland</team>
    <team score="0">Scotland</team>
    <team score="3">Morocco</team>
% set gamedoc [dom parse $gamedata]

xsldata was set to the first xsl example from the What kind of language is XSLT? essay. That is:

% set xsldata {
         <xsl:transform xmlns:xsl="" version="1.0">
            <xsl:template match="results">
                        Results of Group <xsl:value-of select="@group"/>
                                Results of Group <xsl:value-of select="@group"/>
            <xsl:template match="match">
                        <xsl:value-of select="team[1]"/> versus <xsl:value-of select="team[2]"/>
                    <p>Played on <xsl:value-of select="date"/></p>
                            <xsl:value-of select="team[1] "/> 
                            <xsl:value-of select="team[1]/@score"/>,
                            <xsl:value-of select="team[2] "/> 
                            <xsl:value-of select="team[2]/@score"/>

% set soccerstyle [dom parse $xsldata]
% $gamedoc xslt $soccerstyle gamehtml
% $gamehtml asXML
        Results of Group A</title>
        Results of Group A</h1>
        <h2>Brazil versus Scotland</h2>
        <p>Played on 10-Jun-1998</p>
        <h2>Scotland versus Morocco</h2>
        <p>Played on 23-Jun-1998</p>

Loading XML from file with the right encoding settings

tDOM provides some helpers for this in the tdom.tcl lib distributed with the tDOM. Cited from Rolf Ade's answer in tdom again - BOM and/or encoding problems & how to create <?xml ...?> node? , comp.lang.tcl, 2008-05-22

tDOM::xmlOpenFile expects a filename and returns a file channel handle, which
is readily fconfigure'd and seek'ed to get feeded into a dom parse -channel ...
Please note, that the proc opens a channel and returns that. That channel will
not magically go away, if you're done with it. It's your responsibility to
close that channel, if you don't need them anymore. So, a typical use pattern
(sure, not the only) is
set xmlfd [tDOM::xmlOpenFile $filename]
set doc [dom parse -channel $xmlfd]
close $xmlfd

tDOM::xmlReadFile is just a wrapper around tDOM::xmlOpenFile. The pattern is

set doc [dom parse [tDOM::xmlReadFile $filename]]

and you're done. No leaking file channels, filename in, DOM tree out.

Preserving Whitespace

PYK 2014-07-26: I was looking for a way to parse HTML while preserving newline characters in <pre> elements. In my case, -keepEmpties did the trick. See Also:

How to apply an XSLT transformation that includes spaces to an XML doc using tDOM? , 2011-10-26.
asymmetry in tDOM XML parsing and rendering , comp.lang.tcl, 2008-04-11


Uhm, this "full compliant" XSLT support is a little bit to much said - Jochen would have done better, if he had used my "almost compliant".

Don't get this wrong. It is true, that tDOM's XSLT support was greatly improved over the last releases. I'm pretty sure, you could use every 'real live' XSLT stylesheet with it, with correct result. I won't confuse you with outlying nifty difty XSLT details, therefore I omit the list of things that are not quite right.

There are (prominent) tools out there, that don't do it better than tDOM's XSLT engine, due to my extensive testing, but nevertheless claim since a couple of months 100% XSLT compliance, which is simply not completely true, and nobody bothers.

So just use tDOM's XSLT and you will be happy with it. It's only, that I know my business and "full compliant" is not 100% true. Even the missing outlying details will be added, in the next months, for sure. I wonder, what Jochen then will write, in the announcement ;-).

The XPath support is now indeed really very compliant and complete. de.

skm 2005-03-11 Many of the links here in Further Readings are stale. Does anyone have up-to-date locations for these papers? thanks.

LV: Note that even though the web site shows no release since 2004, email on the tdom mail list encourages people to use the CVS to fetch the latest version of code, which developers assure continues to be updated. Note that 64 bit users need to get the cvs version of tdom to get it working properly, according to the developer.

Also note that appears to have the tdom releases that are being performed.

LV 2007-09-11:

Just a note - if you build tdom from source, do a "make test" and see a crash, try rebuilding tdom with the --disable-tdomalloc flag; on my SPARC Solaris 9 system, this resolved the crash.

Getting the Current Namespace Mapping for a Node

DKF: It came up in comp.lang.tcl recently that Gerald Lester needed access to the current namespace mapping for an arbitrary DOM node (parsing XML Schema and WSDL requires this sort of thing). Rolf Ade told us how:

Given that the variable node2 holds the node command, for which you
want to know all prefix-URI mappings in scope, do
$node2 selectNodes namespace::*

This returns a list of two-element lists (i.e. pairs). Of each pair, the first element is either the literal "xmlns" (stating that this is the description of the namespace of unqualified elements) or "xmlns:" followed by a string local namespace name (stating that this is the description of a named namespace and that elements and attributes in that namespace will be using qualified names). The second element of the pair is the URI that characterises the namespace (which need not resolve to anything).

Note (for XML neophytes) that unqualified attributes are always in no namespace at all (unlike unqualified elements).

LV 2007-10-09: Anyone have an example of using tDOM to validate XML using a DTD?

See the page tnc for that.

LV: from comp.lang.tcl, we read:

>  2. I evidently don't understand the domNode man page. For the 
>     "getAttribute" method it says: 

>        getAttribute attributeName ?defaultValue? 
>           Returns the value of the attribute attributeName. If 
>           attribute is not available defaultValue is returned. 

>      It also doesn't give any example(s). 

> Can someone point me to some sample code? 

If I have a Dom Document $doc Which has an element somewhere:

<Foo Bar="baz">Stuff</Foo> 
set $node [$doc getElementsByTagName "Foo"] 
puts [$node getAttribute "Bar"] 

will print:


male 2010-02-24 - Sorting nodes in tdom

CMcC 2010-04-13 21:05:27:

I was having some confusion with [$node attributes] and xml namespaces. evilotto helped me decode what it returns, and I record the findings for posterity.

attributes may return a singleton. In that case, the attribute name is just that.

attributes may return a three-element list. In that case it may be approximated as [lassign $a name namespace uri] ... however: the uri may be empty and the name and namespace equal. In that case, the attribute appears to be a definition of the uri for the namespace given by $name, although the uri thus defined is not returned in the uri field, the uri-defining attribute is named as if it were $ns:$ns. Finally, the {xmlns {} {}} form appears to be special, and to indicate that the xmlns namespace's uri is being defined.

There. Clear as mud. No wonder XML is so popular (?)

aricb 2010-06-17:

An XML declaration is a processing instruction along the lines of <?xml version="1.0" encoding="UTF-8" standalone="no" ?> at the beginning of an XML document. As nearly as I can determine, the recommended way to put this line in a tDOM-generated XML file is something along the lines of:

puts $xmlfile "<?xml version=\"1.0\" encoding=\"UTF-8\" standalone=\"no\" ?>"

In other words, tDOM doesn't provide any facilities for outputting XML declarations (see [L2 ] and [L3 ]).

However, when parsing an XML file with tDOM, you can capture the value of the XML declaration's encoding attribute using:

dom parse [tDOM::xmlReadFile $filename encStr]

the value will be stored in $encStr (see this google thread ).

DKF: Note that the XML declaration is not formally a processing instruction, though it uses the same basic syntax.

Historical was terminated around 2010-11

bovine set up the github project with a mirror of the old website and a fork from the repository.

makr kept as mirror of the old CVS repository.


I recently compiled tdom 0.8.0 on Windows XP successfully with threads enabled, but when doing a package require from within Tcl 8.4.7 I get the following error, "too many nested evaluations (infinite loop?)" when doing the package require tdom command. Any ideas? Thanks in advance.

RS: Oh yes, a silly bug - in the file tdom.tcl, comment out the line

package require tdom

a file can't require a package during providing it :)

snichols: Thank you very much. That fixed the issue.

AK 2006-08-02: When was recently ? According to Rolf Ade this problem was fixed Sep 29, 2004. Both the package index generated by the TEA Makefile, and the one found in the 'win' directory load the shared library (i.e. DLL) first, then source tdom.tcl. As the DLL runs the C equivalent of 'package provide tdom' the 'package require tdom' executed by 'tdom.tcl' is satisfied and will not loop.


escargo 2008-02-38: The "official home" does not provide any way to submit bug reports. I did report a problem to the Yahoo group (now defunct), since seemed to be the only resort available.

HaO 2014-09-16: Rolf Ade said in a private conversation on the 2014 European TCL User meeting that he maintains tdom actively (thank you) and asked if there is something missing... The fossil repository [L4 ] offers a ticket system which might be on his radar.


This tightly-coded extension emphasizes speed and memory economy. In contrast to the "Pure Tcl" TclDOM, it bests leading Java DOM implementations by an order of magnitude (!) in both processing speed and memory demand. Jochen also exploits tDOM's expressivity to offer a nice HTML reader, XML validator--called tnc--and XSLT engine. tDOM is in production at several commercial installations.

0.8.3 doesn't compile for Tcl version 8.6. Use trunk or a later version instead.

MSW: now understands why tDOM crashed for him ... obviously you shouldn't be generating variables more than once (like two consecutive [<domDoc> documentElement root] in different functions make tDOM trip). He's still intrigued by appended nodes not being addressable (no localName, no URI, not reachable via [selectNodes]).


set doc [dom createDocument foo]
set root [$doc documentElement]
# append a node
set node [$root appendChild [$doc createElement bar]]
# all of the following return a value == $node
$root firstChild
lindex [$root selectNodes /foo/bar] 0
lindex [$root selectNodes //bar] 0
lindex [$root selectNodes /*/*] 0
lindex [$root getElementsByTagName bar] 0

# do it again
set node1 [$root appendChild [$doc createElement bar]]
# all of the following return a value == $node1
[$root firstChild] nextSibling
lindex [$root selectNodes /foo/bar] 1
lindex [$root selectNodes {/foo/bar[2]}] 0
lindex [$root selectNodes //bar] 1
lindex [$root selectNodes /*/*] 1
lindex [$root getElementsByTagName bar] 1

return of "$node attributes" (and xmlns:xxx attributes)

oehhar 2018-05-14: Rolf wrote on the chat of the return value of the $node attributes ?attributeNamePattern? command:

In case of an "ordinary" namespaced attribute, the sublist elements are {<localname> <prefix> <namespace_uri>}.

In the special case of an xml namespace declaration it is {<the prefix defined> <localname> <namespace_uri>}. Of course, the prefix defined and the localname are equal. And some of the (somewhat ... special) recommendations say, that namespace declaration attributes are not in any namespace.

My example for xml namespace declarations

The issue arised within tcl ws bug 584bfb77 .

Example script (real example in the upper ticket):

<?xml version="1.0" encoding="utf-8"?>
<ps1:t1 xmlns:ps1="uri1" xmlns:ps2="uri2">
  <ps1:t2 type="ps2:type"></ps1:t2>

How do I get the attributes "xmlns:*" from the node "ps1:t1" ?

Here is the example script:

set xml {<?xml version="1.0" encoding="utf-8"?>
<ps1:t1 xmlns:ps1="uri1" xmlns:ps2="uri2">
  <ps1:t2 type="ps2:type"></ps1:t2>
dom parse $xml doc
$doc documentElement top
foreach attributelist [$top  attributes] {
    lassign $attributelist localname prefix uri

    # ignore attributes in namespaces and with different local names
    if {$uri ne "" || $prefix ne $localname} {continue}

    # Attribute name of a namespace prefix
    set attributename "xmlns:[lindex $attributelist 0]"

    # This will filter out any non-namespace declaration attributes
    if {![$top hasAttribute $attributename]} {continue}

    puts "$attributename = [$top getAttribute $attributename]"

with the output:

xmlns:ps1 = uri1
xmlns:ps2 = uri2

Here is the implementation in client.tcl of tclws: client.tcl line 2187 - 2203

XPath version

AMG: tDOM implements XPath 1.0. Here is the relevant quote from the documentation:

The selectNodes method implements the "XML Path Language (XPath) Version 1.0" W3C recommendation 16 November 1999 ( ). Look at these documents for a deeper understanding of the functionality.

Are there any plans to implement XPath 2.0, 3.0, or 3.1?

Parameterized XPath

AMG: tDOM directly supports parameterizing XPath using Tcl variables. Since the caller doesn't have to perform string concatenation, performance and security are improved. See also: Brace your expr-essions and Injection Attack.

Two different variable reference syntaxes are available, the choice of which depends on context. In places where a value is expected, use $var. In places where an element name is expected, use %var.

What if the Tcl variable contains the name of an attribute? @$var and @%var do not work, since an attribute name is neither a value nor an element name. The solution is to use attribute::%var.

Easier XPath attributes

AMG: In the common case, you already know what your attribute names are, since you're putting them directly in your XPath query. (If you're using @* or similar, please look away.) Getting the attribute values back from [$doc selectNodes] is a nuisance step which could be avoided by not including the already-known attribute names in the return value. Here's a simple wrapper that makes XPath attribute lookup easier:

proc xmlAttrs {origin xpath} {
    lmap node [uplevel 1 [list $origin selectNodes $xpath]] {lindex $node 1}
proc xmlAttr {origin xpath} {
    if {[set attrs [uplevel 1 [list xmlAttrs $origin $xpath]]] eq {}} {
        return -code error "XPath query failed to match: $xpath"
    } elseif {[llength $attrs] > 1} {
        return -code error "XPath query matched multiple: $xpath"
    } else {
        lindex $attrs 0

For example, the following returns all the ID attribute values throughout the whole document:

xmlAttrs $doc {//@id}

Contrast with either of the following:

lmap node [$doc selectNodes {//@id}] {lindex $node 1}
lmap node [$doc selectNodes {//@id}] {dict get $node id}