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From: David Welton <davidw@master.debian.org>
Subject: mod_dtcl 0.4.2 - server parsed tcl for apache
Date: 1 Feb 1999 20:56:46 -0800
Hello,
I have, as the version number would indicate, made several releases of
mod_dtcl in the past, but I would like more people to use, test, and
comment on it, so I am publicizing it more openly. I welcome all
comments, suggestions, ideas and thoughs, and would appreciate it if
they were directed to the mailing list.
I am including the text version of mod_dtcl's readme:
WHAT IS mod_dtcl ?:
* mod_dtcl is a free/open source implementation of server parsed
[1]Tcl, under [2]Apache, distributed under the terms of the GNU
GPL. It allows you to tightly integrate html with Tcl, a widely
used scripting language with many years of development invested in
it. This is an ideal combination, allowing you to greatly extend
what you could do with plain html. Because Tcl is such a widely
used language, there is a large amount of documentation for it,
both on the net and books. There are also many external Tcl
modules that you can load into mod_dtcl, to create images, access
databases, etc. Apache, is, of course, the world's most popular
web server. If you aren't reading this from the web pages, they
are available at [3]"http://comanche.com.dtu.dk/dave/.
[4]Install mod_dtcl!
EXAMPLES:
* The [5]examples.ttml file has a few very limited examples of what
is possible with mod_dtcl. You need to make it accessable to the
web server in order to be able to view it. Put it in your
public_html directory or something. Have a look at my rough
[6]benchmarks - although they are unscientific, the results are
interesting.
COMMANDS:
Special mod_dtcl commands
* hputs ?-error? - like puts, but to the client instead of stdout.
The error option permits you to send an 'error message' to the
apache log file, at the NOTICE level.
* hgetvars - get the environmental vars. This is in a seperate
command so as not to make the server do this every time you load a
.ttml file. ENVS and VARS are the two associative arrays loaded.
ENVS contains environmental variables, VARS contains all the 'cgi'
variables. Look in the examples.ttml file to see how these work.
* include filename - include a flat file. Useful for including HTML
files.
SUPPORT:
There is a mailing list at [7]mod_dtcl@lists.prosa.it. Mod_dtcl is
currently alpha software (meaning that it is subject to change),
however, due to the relative simplicity of the design, it is fairly
stable, and performs well. If you have any questions or comments,
please send them to the mailing list, or to me.
TODO:
* Decide whether to create a new interpreter for each page, or use a
seperate namespace for each one. The namespace solution is faster,
and allows things like global configs, however, it is possible to
create global variables that are persistant within one apache
process. The Tcl_Create method seems cleaner, but does not permit
global config files, and might be slower.
* Decide on standard opening and closing tokens - currently using <+
and +> for no particular reason.
* Security review.
* There ought to be a way to make it so things like while {1}
doesn't go ape and make the process run away. I.e., create a limit
on the maximum execution time.
* Lots more commands.. like php, to make life easier. Some things
will have to be done in the module itself, I think, like cookie
things, because they deal with headers. Other things could
probably be implemented in tcl, if the speed loss isn't too great.
PHP would be a good place to look for examples.
* Make file uploads work. Once again, PHP has some code which does
this, but it looks like a hairy mime mess. It's a pity that Apache
doesn't have a standard way of getting stuff out of headers,
without doing most of the parsing yourself.
* Configurations options: safe mode, ???.
* Use flex as a lexer instead of my own, handwritten one? Not much
of a point, I guess, but it might be informative/interesting/fun.
* Long term: it would be neat to build something that could use any
one of a variety of languages, like Perl, Python, Guile..whatever.
* Long term: maybe have a seperate process running somewhere that
all the different server processes could talk to, similiar to how
java servlets work (ridruejo@esi.us.es).
WHY:
Why mod_dtcl when there are already so many other server parsed
implementations?
* Because it was fun to do:-)
* Because Tcl is a common and relatively well known language.
[8]PHP, while nice, is not really used much outside the web. It's
easier, and more practical, to learn a more general language, that
can be used outside of the web, for many other applications. Also,
Tcl has had many more years than PHP to mature, and it has a large
user base.
* Because mod_perl is a big heavy chunk of Perl that seems like
overkill for many things. I didn't really investigate it all that
thoroughly though:-) Mod_dtcl aims to be more lightweight - it
doesn't get involved in the server config files, for instance. If
someone were interested, they could write a companion module
"mod_tcl_config". Just an idea...
INTERNALS:
A brief description of how it works. For each page requested, a new
tcl namespace is created within the global namespace. The module then
reads through the page, aggregating plain HTML into big "hputs"
statements, and anything between the delimiters ( <+ and +> ) as
regular tcl. After this is done, the whole script is eval'ed and sent
to the client. After it is eval'ed, the namespace that it was run in
is destroyed, so as to destroy local variables. Read the code for more
info:-)
THANKS:
I would like to thank Daniel Ridruejo for furnishing me with the web
space, Rolf Ade, and the various people subscribed to the mod_dtcl
mailing list for ideas, comments and suggestions.
[9]Send me mail about mod_dtcl!
mod_dtcl is Copyright [10]David Welton 1998
$Id: readme.html,v 1.4 1999/01/30 22:01:19 davidw Exp $
References
1. http://www.scriptics.com/
2. http://www.apache.org/
3. http://comanche.com.dtu.dk/dave/
4. file://localhost/home/davidw/web/mod_dtcl/INSTALL.html
5. file://localhost/home/davidw/web/mod_dtcl/examples.ttml
6. file://localhost/home/davidw/web/mod_dtcl/benchmark.html
7. mailto:mod_dtcl@lists.prosa.it
8. http://www.php.net/
9. mailto:davidw@debian.org
10. http://www.efn.org/~davidw
Thankyou,
--
David Welton http://www.efn.org/~davidw
www.prosa.it - Debian GNU/Linux - www.debian.org
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