<!doctype linuxdoc system>

<article>

<title>The Linux Tcl and Tk HOWTO
<author>Luca Rossetti <url url="mailto:lukaros@tin.it" name="lukaros@tin.it">
<date>v0.2, 07 November 1998
<abstract>This document describes the Linux approach to Tcl, a scripting langua
ge.
 It is an easy to learn interpreted language that uses a typeless approach to
 achieve a higher level of programming and a rapid application development.
 The Tk toolkit is a programming environment for creating graphical user interf
aces
 (GUI) under X Window System. Their capabilities include the possibility to
 extend and embed in other application, rapid development and ease of use. Toge
ther,
 Tcl and Tk provide many benefits both to application developer and user. Tk-ba
sed
 interfaces tend to be much more customizable and dynamic than those built with
 one of the C or C++ based toolkits. Tk implements the Motif look and feel.
 A great number of interesting X applications are implemented entirely in Tk,
 with no new application-specific commands at all.
<sect>Introduction<label id="introduction">
<p>

This is the Linux Tcl and Tk HOWTO. It is intended as a Linux reference
 covering everything you should know concerning installation, configuration
 and an introduction to development under Tcl and Tk. History and some pros
 and cons about Tcl and Tk under Linux are analized, and references are given
 to many other sources of information on a variety of topics related to this
 simple but powerful scripting language.

If you ever rebuilt your Linux kernel inside X using the command
<code>make xconfig
</code>

you surely managed to face the strenght of this simple but powerful scripting
 language.

After executing the first step of kernel rebuilding, a script called kconfig.tk
 is executed via wish (the Tcl intepreter). The Linux Kernel Configuration wind
ow
 appears. Instead of answering a series of questions, this X-based configuratio
n
 utility allows you to use checkboxes to select which kernel options you want
 to enable.

The system stores your last configuration options so that every time you
 run it, you need only to add or remove some checks and you don't need to reent
er
 the whole set of option. Moreover you can fill the whole (or part of the) list
 of kernel option the order you want. After this simplified step you can rebuil
d
 your kernel in the traditional way.

There's actually another famous case. Have you ever used "printtool"
 ? (Printer Config Tool (C) Copyright 1994 by
<url url="http://www.redhat.com" name="Red Hat Software"> - author: Michael
 Callahan).
If you installed a Red Hat distribution you happily managed to
 use it to set up printing services . Well, printtool front-end is mainly a
 Tcl/Tk script.

For those who don't know Red Hat let me tell you how you can easily configure
 your printers just filling some textboxes and filling in some checkboxes.

The program itself takes care of setting up printing services through the
 creation of spooling directory, writes /etc/printcap file and the printer's
 filter, reloads lpd and tests your filter with ascii or postscript pages. It
 allows you manipulate ghostscript options (i.e. choose up to 8 pages per outpu
t
 page and setting margins), has an help-on-line and many more features.

What is the difference compared to other service-printing implementation?

Everything is achieved by using Tcl/Tk as a "glue" between consolidated
 application and operating with normal Linux configuration files in a visual
 and interactive window under X-Window. No new application-specific commands
 were written at all.
<sect1>Purpose of this document
<p>

Currently the purpose of the document is limited to giving initial references
 to Linux users; in future versions I will try to incorporate a small "Programm
ing
 Tutorial".
Let me state that again: this is not (and doesn't want to substitute)
 an omnicomprehensive "user manual" or "reference" for Tcl and Tk development
 and programming - it's just a starting point for Linux users.

The author's concept of reference manual coincides with the definition
 of man pages and many people learn Tcl/Tk from these basic source of informati
on.
 These files are a part of the source code distribution and are installed on
 your Linux box. You will be able to access the Tcl/Tk manual pages through
 the man command.

Many structured and complete programming tutorials have been written in
 order to let the new user begin hacking with Tcl/Tk; tons of other material
 are available in the Internet. Interpreting Tcl/Tk philosophy I won't try to
 reinvent the wheel, I will manage to glue the huge amount of material already
 available.

I suggest you to have a look at the other documents listed in the
<ref id="references" name="References section"> in order to find where to retri
eve
 specific information about Tcl and Tk.
<sect1>What you should know before reading
<p>

In order to understand the abc of Tcl/Tk you shouldn't be a programming-guru,
 command sintax is very simple. Basically you have to be familiar with:
<itemize>
<item>simple programming concepts;
<item>using very common unix commands and/or utilities;
<item>having access to the Internet;
<item>using ftp.
</itemize>
<sect1>New versions of this document
<p>

Newer versions of this document will be uploaded to ftp site:
<url url="ftp://sunsite.unc.edu/Linux/docs/HOWTO/" name="ftp://sunsite.unc.edu/
pub/Linux/HOWTO/">
 and will be available on all other mirrors.

Hypertext and other versions of this and other Linux HOWTOs are available
 mainly at
<url url="http://sunsite.unc.edu/LDP/lpd.html" name="sunsite.unc.edu/LDP/lpd.ht
ml">
 and <url url="http://www.linux-howto.com" name="www.linux-howto.com"> and on
 many other Mirror World-Wide-Web sites.

I will try to incorporate in
<url url="http://space.tin.it/computer/tlqhr/" name="my Web-Page"> the most
 recent html and sgml version of the document. Most Linux CD-ROM distributions
 include the HOWTOs, often in a subdir of /usr/doc/ directory, and you can also
 buy printed copies from several vendors.

Sometimes the HOWTOs available from CD-ROM vendors, ftp sites, and in hardcopy
 format are out of date. If the date on this HOWTO is more than six months in
 the past, then a newer copy is probably available on the Internet.

If you make a translation of this document into another language, drop
 me a line and I'll include a reference to it here.
<sect1>Revision History
<p>
<itemize>
<item><bf>Version 0.1</bf>: 28 October 1998 - first version;
<item><bf>Version 0.2</bf>: 07 November 1998 - deep restyling and lifting.
</itemize>
<sect1>Feedback and other stuff
<p>

I rely on you, the reader, to make this HOWTO useful. If you have any suggestio
ns,
 corrections, or comments, please send them to me, (
<url url="mailto:lukaros@tin.it" name="Luca Rossetti"> ), and I will try to
 put them in the next revision.

If any of the links mentioned in this document becomes unavailable or changes,
 please notify me immediately so that I can update and/or remove the link.

I am willing to answer general questions about Tcl/Tk and Linux as best
 as I can. Before doing so, please read all of the information in this HOWTO,
 and send me detailed information about the problem.

If you publish this document on a CD-ROM or in hardcopy form, a complimentary
 copy would be really appreciated. E-mail me and I will send you back my postal
 address.

In many section I mention publishing companies or commercial URL sites:
 I really don't work for these guys.
<sect1>Credits
<p>

Most of the information in this HOWTO comes from Dr. Ousterhout's
<url url="http://www.scriptics.com" name="Scriptics">  and Larry W. Virden
<url url="http://www.tclfaq.wservice.com/tcl-faq/" name="comp.lang.tcl FAQs">
 .

I would like to thank the
<url url="http://www.pluto.linux.it/" name="PLUTO">  Italian Linux User Group
 and the whole volunteers of
<url url="http://www.pluto.linux.it/ildp/" name="ILDP"> (Italian Linux Document
ation
 Project) especially Eugenia Franzoni and Giovanni Bortolozzo for their feedbac
k.
<sect1>Distribution Policy
<p>

This document is Copyright 1998 by
<url url="mailto:lukaros@tin.it" name="Luca Rossetti">.

This document is distributed in the hope that it will be useful to the
 reader: of course it is considered to be without any warranty; without even
 the implied warranty of merchantability or fitness for a particular purpose.
 This HOWTO is free documentation; you can redistribute it and/or modify it
 under the terms of the
<url url="http://sunsite.unc.edu/LDP/LDP-COPYRIGHT.html" name="LDP COPYRIGHT">
 .

Please read the
<url url="http://sunsite.unc.edu/LDP/LDP-Manifesto.html" name="LDP Manifesto">
 for more details.
<sect>Tcl/Tk History
<p>

Tcl/Tk originated with
<url url="mailto:ouster@scriptics.com" name="Dr. John Ousterhout"> (pronounced
 "Oh'-stir-howt") while teaching at University of California, Berkeley, Califor
nia.
 He actually started implementing it when he got back to Berkeley in the spring
 of 1988; by summer of that year it was in use in some internal applications,
 but there was no Tk. Read about the history of Tcl/Tk directly from its author
's
 words at
<url url="http://www.scriptics.com/scripting/tclHistory.html" name="www.scripti
cs.com/scripting/tclHistory.html">.
<sect1>Cronology
<p>
<itemize>
<item><bf>1989:</bf> The first external releases of Tcl and beginning of Tk imp
lemention;
<item><bf>1991</bf>: First release of Tk;
<item><bf>1994:</bf> Dr. Ousterhout was hired by Sun Microsystems, Inc.: he was
 a Distinguished
 Engineer and led the Tcl project.
<item><bf>April/May 1997:</bf> the Sun research group responsible for Tcl devel
opment
 were spun off into a Sun business group called SunScript. However, things chan
ged
 again soon afterwards. You can read more about that evolution selecting "SunSc
ript_story"
 at URL:
<htmlurl url="http://starbase.neosoft.com/&percnt;7Eclaird/comp.lang.tcl/" name="Su
nScript-Story"> .
<item><bf>August 1997:</bf> a Tcl Consortium was formed. 
<item><bf>February 1998:</bf> Dr. Ousterhout left Sun to create
<url url="http://www.scriptics.com/" name="Scriptics">, a company dedicated
 to scripting tools, applications, and services. According to
<url url=" http://www.scriptics.com/about/news/qa.html" name="www.scriptics.com
/about/news/qa.html">,
 core Tcl and Tk remain free, with the team at Sun continuing work right now
 on Tcl/Tk 8.1. After the next release, the intention is that work on the core
 will migrate from Sun to Scriptics, with the Sun team will focus more on Tcl
 extensions and applications.
<item><bf>April 23, 1998:</bf> the Association for Computing Machinery
<url url="http://www.acm.org/" name="ACM"> awarded the 1997 Software System
 Award to John Ousterhout and Scriptics (
<url url="http://www.acm.org/awards/" name="www.acm.org/awards/">). This award
 is given to an institution or individual recognized for developing a software
 system that has had a lasting influence, reflected in contributions to concept
s,
 in commercial acceptance, or both.
</itemize>
<sect>What is Tcl/Tk
<p>
<sect1>What is Tcl?
<p>

Tcl is the acronym for "Tool Command Language" (it is pronounced "tickle").
 Tcl is actually divided into two things: a language and a library.

Tcl is a simple textual programming language, intended for issuing commands
 to interactive programs such as text editors, debuggers and shells. It has
 a simple syntax and it is also programmable.

Tcl users can write command procedures to provide more powerful commands
 than those given in the built-in set.

Second, Tcl is a library package embeddable in applications. The Tcl library
 consists of a parser for the Tcl language, routines to implement the Tcl built
-in
 commands, and procedures which allow each application to extend Tcl with addit
ional
 commands specific to that application. The application program generates Tcl
 commands and passes them to the Tcl parser for execution.

Commands may be generated by reading characters from an input source, or
 by associating command strings with elements of the application's user interfa
ce,
 such as menu entries, buttons, and other widgets. When the Tcl library receive
s
 commands it parses them into component fields and executes built-in commands
 directly.

For commands implemented by the application, Tcl calls back to the application
 to execute the commands. In many cases commands will make recursive invocation
s
 of the Tcl interpreter by passing in additional strings to execute (in fact
 procedures and conditional-looping commands all work in this way). An applicat
ion
 program can obtain many advantages by using Tcl for its command language:
<itemize>
<item>Tcl provides a standard syntax: once users know Tcl, they will be able
 to issue commands easily to any Tcl-based application.
<item>Tcl succeeds to provides programmability. All a Tcl application needs to
 do is to implement a few application-specific low-level commands. Tcl provides
 many utility commands and a general programming interface for building up comp
lex
 command procedures. By using Tcl, applications need not reimplement these feat
ures.

<item>Extensions to Tcl, such as the Tk toolkit, provide mechanisms for communi
cating
 between applications by sending Tcl commands back and forth. The common Tcl
 language framework makes it easier for applications to communicate with one
 another.
</itemize>

It is important to note that Tcl was designed thinking that the programmer
 should actually use two or more languages when designing large software system
s.
 One for manipulating complex internal data structures, or where performance
 is important, and another, such as Tcl, for writing very small scripts that
 glue together the other pieces, providing hooks for the user to extend.

For the Tcl script writer, ease of learning, ease of programming and ease
 of gluing are more important than performance or facilities for complex data
 structures and algorithms.

Tcl was designed to make it easy to drop into a lower language when you
 come across tasks that make more sense at a lower level. In this way, the basi
c
 core functionality can remain small and one need only bring along pieces that
 one particular wants or needs.

One answer to "What is Tcl?" can be found at
<url url="http://www.NeoSoft.com/tcl/whatistcl.html " name="www.NeoSoft.com/tcl
/whatistcl.html">
 .
<sect1>What is Tk?
<p>

Tk (pronounced "tee-kay") is an extension to Tcl which provides the programmer
 with an interface to the X11 windowing system . Note that Tk has been successf
ully
 compiled under X11 R4, X11 R5, X11 R6, as well as Sun's NeWS/X11 environments.


Many users will encounter Tcl/Tk via the "wish" command. Wish is a simple
 windowing shell which permits the user to write Tcl/Tk applications in a proto
typing
 environment.

At present Tcl/Tk cannot handle Japanese, Chinese, Korean, .... language
 fonts.
<sect1>Extensions
<p>

Since Tcl is so easy to extend, many try to share extensions, including
 the popular itcl, <url url="http://www.tcltk.com/itcl/" name="[incr Tcl]">,
 ObjectTcl, TclX, <url url="http://tix.mne.com/" name="Tix ">, and
<url url="http://www.tcltk.com/blt/" name="BLT">.

These extensions, of course, require an extended Tcl interpreter. Moreover,
 many Tcl free applications require a particular Tcl extension to run.

One of the most popular extension is called
<url url="http://expect.nist.gov" name="Expect">.
It allows you to place a
 friendly front-end inside most command-line based UNIX applications, such as
 ftp, telnet, rlogin, passwd, fsck, and so on.

A complete list of Tcl/Tk extensions can be found at URL
<url url="http://www.scriptics.com/resource/software/extensions/" name="www.scr
iptics.com/resource/software/extensions/">.
<sect1>Supported Platforms
<p>

This section contains information about Tcl 8.0 and Tk 8.0, the most recent
 version of Tcl/Tk. They were originally released on August 18, 1997 and the
 most recent patch releases (8.0.3) were made on September 3, 1998.

When you download Tcl and Tk you get two programs, wish and tclsh, supporting
 script libraries, and on-line reference documentation. These programs are gene
ral
 purpose platforms for writing applications with Tcl. Wish includes the graphic
al
 user interface toolkit Tk. The packages are ready to use after installation.


Tcl 8.0 and Tk 8.0 run on most releases of the following operating systems:

<itemize>
<item>Windows 95
<item>Windows NT
<item>Solaris and SunOS
<item>Linux
<item>HP-UX
<item>SGI
<item>IRIX
<item>Digital Unix
<item>AIX
<item>SCO Unix
<item>Most other Unix-like operating systems Macintosh (68K and Power Mac)
<item>Pre-compiled releases are available for different Linux distribution.
</itemize>
<sect>Installing and getting started with Tcl and Tk
<p>

Most modern distribution include Tcl and Tk. Rpm and deb packages with
 precompiled binaries are avalaible for Red Hat, SuSE and Debian distributions
 (that'll make installation easier).

A modern distribution standard installation will include Tcl/Tk as it is
 needed by many configuration tools running mainly under X.

Tcl and Tk are distributed freely in source form via the Internet. There
 are no restrictions on their use and no licenses or royalties are needed (see
 the <ref id="license" name="license.terms"> section for complete information).


Many more Tcl/Tk scripts and extensions are also available freely.
<sect1>Downloading the Core Distributions
<p>

The Tcl/Tk core consists of the Tcl and Tk libraries, plus the wish and
 tclsh applications, associated documentation, script libraries, and demonstrat
ive
 applications. The primary FTP site for this information is
<url url="ftp://ftp.scriptics.com/pub/tcl/" name="ftp.scriptics.com/pub/tcl/">.


The primary HTTP site is
<url url="http://www.scriptics.com/software/download.html" name="www.scriptics.
com/software/download.html"> .
<sect1>Installation
<p>

Unless already available for your Distribution in proprietary packages
 you'll want to download the source release. You'll need both Tcl and Tk source
s.
 This procedure refers to the second case.

Choose between compressed tar and gzipped tar format.

Compressed Tar Files

Tcl sources (tcl8.0.3.tar.Z): compressed tar file (about 2.4 Mbytes). Tk
 sources (tk8.0.3.tar.Z): compressed tar file (about 3.3 Mbytes).

Gzipped Tar Files

Tcl sources (tcl8.0.3.tar.gz): gzipped tar file (about 1.5 Mbytes). Tk
 sources (tk8.0.3.tar.gz): gzip'ed tar file (about 2.1 Mbytes).

When you retrieve one of these files, you will get a compressed tar file
 with a name like tcl8.0.3.tar.gz or tcl8.0.3.tar.Z. The files are identical
 except for the technique used to compress them (.gz files are generally smalle
r
 than .Z files).

To unpack the distribution, invoke shell commands like the following, depending
 on which version of the release you retrieved:
<code>gunzip -c tcl8.0.3.tar.gz
</code>

or
<code>tar xf - zcat tcl8.0.3.tar.Z
</code>

or
<code>tar xf - unzip tcl80.3.zip
</code>

Each of these commands will create a directory named tcl8.0.3, which includes
 the sources for all platforms, documentation, and the script library for Tcl
 8.0. To compile and install the distribution, follow the instructions in the
 README file in the distribution directory. Be sure to compile Tcl before Tk,
 since Tk depends on information in Tcl.
<sect1>The Contributed Archive
<p>

There are many other freely available packages for Tcl and Tk, including
 both scripts written in Tcl and extensions written in C or C++. These packages
 include database applications and network access, a graphical user interface
 builder, the expect program, additional Tk widgets, and dozens of other things
.
 The primary site for the Tcl/Tk archive is
<url url="ftp://ftp.neosoft.com/pub/tcl" name="ftp.neosoft.com/pub/tcl">.
<sect1>Mirror Sites
<p>

Several other sites around the world mirror the whole or part of the material
 from the core site and the contributed archive; you may find more useful to
 retrieve information from a mirror site that is close to you.

Ftp file "0_mirror" at:
<url url="ftp://ftp.scriptics.com/pub/tcl/" name="ftp.scriptics.com/pub/tcl/">
 for a list of the mirror sites in your country.
<sect1>Which Releases to Use
<p>

Always refer to newer recommended version in section "Tcl/Tk Core" of the

<url url="http://www.scriptics.com/software/download.html" name="Scriptics Soft
ware Central page">.

At the time of this writing, recommended releases are the latest (Tcl 8.0.3
 and Tk 8.0.3), which were released in September, 1998. Tcl 8.0 contains a new
 bytecode compiler that can speed up execution by a factor of 2-10x. It also
 provides namespaces, binary I/O, and several other new features.

Tk 8.0 is the first release to provide native look and feel on Macintoshes
 and PCs. Tk 8.0 also supports application embedding and has a new portable
 font mechanism. Both Tcl 8.0 and Tk 8.0 provide additional features in the
 Safe-Tcl security model.
<sect1>Where to report problems, bugs, or enhancements
<p>

Use <url url=" news.comp.lang.tcl" name="comp.lang.tcl"> for public communicati
ons.

The alternative would be to send problems, suggestions, new ideas, etc.
 directly to the author. Email to
<url url="mailto:Ouster@scriptics.com" name="John Ousterhout"> will reach the
 author of Tcl and Tk.

When reporting problems or bugs, be sure to mention all the details needed
 for a correct diagnosis. Basically you will have to describe what hardware,
 operating system and version of Tcl/Tk you are using, if you have made any
 modification or add on and provide, if possible, either a small piece of code,
 or a URL to some code which demonstrates the problem.

If you have software from which you think the community might benefit (either
 a program, function, extension, or simple example), or you have a document,
 magazine or journal article, thesis, project, or even commercial advertisement
,
 be sure to let the appropriate guys know.

There are FAQ maintainers for each of these areas as well as a
<url url="news:news.comp.lang.tcl.announce" name="comp.lang.tcl.announce">
 newsgroup you can use.

It is always worthwhile to submit your contributions directly to the ftp
 site so more folk in the future can benefitthanks to your experience.

To make announcements to the
<url url="news:news.comp.lang.tcl.announce" name="comp.lang.tcl.announce">
 newsgroup, send email with the details to
<url url="mailto:tcl-announce@mitchell.org" name="tcl-announce">. Also, feel
 free to just point folk at your own ftp site or WWW site if you have one which
 can be used .
<sect>Just a little bit of Programming
<p>

Since Tcl is an interpreted language, to run a Tcl program (also called
 a script), you normally pass the script file to the Tcl interpreter, wish,
 for example:
<code>wish hello.tcl
</code>

You can also use wish in interactive mode and type in commands at the command
 line.

There's another standard Tcl interpreter, tclsh, which only understands
 the Tcl language. Tclsh does not have any of the Tk user interface commands,
 so you cannot create graphical programs in tclsh.

Some Tcl freeware applications extend the Tcl language by adding new commands
 written as C functions. If such is the case, you need to compile the applicati
on
 instead of just passing its Tcl code to the wish interpreter. This application
 program, from a Tcl perspective, is really a new version of the wish interpret
er,
 which the new C commands linked in. Of course, the application program may
 be a lot more than merely a Tcl interpreter. (Note: you can also use Tcl's
 auto-loading capability on systems that support it.)
<sect1>The one-minute program in Tcl
<p>

Tcl has a simple structure. Each line starts out with a command, such as
 button and a number of arguments. Each command is implemented as if it was
 a C function. This function is responsible for handling all the arguments.


As a very standard example, the following is the Hello World program in
 Tcl/Tk:
<code>&num; This is a comment
button .b -text "Hello World" -command exit
pack .b
</code>

In this case you have to type the commands interactively to tclsh or wish.

You can also place command into script files and invoke these just like
 shell scripts. To do this for the previous example, rewrite the Hello World
 program as follows:
<code>&num;! /usr/local/bin wish -f
button .b -text "Hello World" -command exit
pack .b
</code>

Put the text inside a file called Hello and make sure that wish is installed
 in /usr/local/bin (otherwise you will have to change opportunely the path).

Make the file Hello executable issuing the command
<code>chmod 775 Hello
</code>

and run it inside X.

You will see a button labelled Hello World inside a window: clicking it
 will close (exit) the window.
<sect>Scripting Language: pros and cons
<p>

To understand the importance and the future of Tcl/Tk I strongly suggest
 to point your web browser at the URL
<url url="http://www.scriptics.com/people/john.ousterhout/" name="www.scriptics
.com/people/john.ousterhout/">
 by <url url="mailto:ouster@scriptics.com" name="John K. Ousterhout ">. You
 will read about the importance and the comparison between scripting (in langua
ges
 such as Tcl) and system programming (in languages such as C and Java).

To read a document about comparisons see
<ref id="prosandcons" name="the comparison discussion">.

Here's a summary of the most important pros and cons about Tcl/Tk.
<sect1>Some of the most common complaints about Tcl
<p>
<sect2>Tcl is interpreted
<p>

The data is primarily treated as strings, programs written in Tcl are slow.
 Tcl 8.x attempts to address this by doing some degree of compilation as well
 as permitting additional variable types.
<sect2>Several characteristics are not intuitive
<p>

Comments are commands rather than traditional comments, numbers beginning
 with 0 are octal, proper use of quoting mechanisms, etc. These aspects are
 covered in the various FAQs.
<sect1>Some of the most pros about Tcl
<p>
<sect2>It is a high-level scripting language
<p>

You need to write a lot less code to get your job done, especially when
 compared to Motif or Win32 applications. In general, the number of Line Of
 Code (LOC) of a software project is one of the most important complexity index
es.

<sect2>Tcl is free
<p>

You can get the sources for free over the Internet from Scriptics Download
 Page or from the FTP site for Tcl.
<url url="http://www.scriptics.com/software/download.html" name="The software c
ore site">
 includes the source code version, as well as binary versions for Windows and
 Macintosh platforms; or, you can get Tcl on a number of CD-ROMs for a nominal
 cost.

Read about Tcl and Tk core free at
<url url="www.scriptics.com/about/news/qa.html" name="www.scriptics.com/about/n
ews/qa.html"> .
<sect2>It runs on many platforms
<p>

Versions exist for UNIX (Linux... of course), Windows and Macintosh. Except
 for a few platform differences, your Tcl scripts will run the same way on all
 systems.
<sect2>It is interpreted
<p>

You can execute your code directly, without compiling and linking (though
 Tcl compilers are available).
<sect2>It is extensible
<p>

It's easy to add your own commands to extend the Tcl language. You can
 write your commands in C or Tcl.
<sect2>It is embeddable in your applications
<p>

The Tcl interpreter is merely a set of C functions that you can call from
 your code. This means you can use Tcl as an application language, much like
 a macro language for a spreadsheet application.
<sect2>Tcl/Tk is Year 2000 (Y2K) compliant
<p>

Read what the creator of the Tcl and Tk core tells about this topic
<url url="http://www.scriptics.com/Y2K.html" name="www.scriptics.com/Y2K.html">
.

<sect>Most Famous Programs using Tcl/Tk
<p>

Apart from the two implementation described in the
<ref id="introduction" name="Introduction">, there are many applications writte
n
 in Tcl/Tk or a combination of Tcl and C. A complete list where to look for
 these implementation is the
<url url="http://www.tclfaq.wservice.com/tcl-faq/part4.html" name="part 4">
 of the frequently-asked questions on Tcl/Tk (FAQs). I suggest you to visit

<url url="http://www.scriptics.com/resource/software/" name="Scriptics' Softwar
e Central">.

Another good starting point is
<url url="http://www.NeoSoft.com/tcl/" name="www.NeoSoft.com/tcl/">.

One of the best Tcl applications running under Linux is called
<url url="http://people.mainz.netsurf.de/&tilde;bolik/tkdesk/" name="TkDesk">
 a window manager and application launcher that works very well.

If you're a Tcl/Tk Linux developer, feel free to
<url url="mailto:lukaros@tin.it" name="send me"> a URL (and a description of
 the work) that I can link to in here.
<sect>References<label id="references">
<p>

For many reasons people often like having a hard-copy manual as a reference
 or like to be helped by other folks online.

Here you can find a selection of reference books, tutorials, www-sites
 and newsgroup.
<sect1>Books
<p>

Many books concerning Tcl/Tk were written and are to be published. I won't
 even try to list them all (<bf>another howto woudn't be enough for that</bf> :
) ). You
 can find much more information plus additional notes at:
<itemize>
<item>
<htmlurl url="http://www.tcltk.com/consortium/resources/books.html" name="www.tcltk.com/consortium/resources/books.html">
<item>
<htmlurl url="http://www.amazon.com/exec/obidos/subst/categories/computer-programming/tcl-tk-article/002-8989352-4516417" name="www.amazon.com/exec/obidos/subst/categories/computer-programming/tcl-tk-article/002-8989352-4516417">
<item>Page: tcl_books.html at URL
<htmlurl url="http://starbase.neosoft.com/&percnt;7Eclaird/comp.lang.tcl/" name="starbase-neosoft-tcl-books">
</itemize>

Here I will try to summarize with some notes the book I know concerning
 the subject, they're all at a basic-medium level. Again, people who know the
 subject, have enough information about where to find advanced level books.

<sect2>Tcl and the Tk Toolkit
<p>

Author:
<url url="mailto:ouster@scriptics.com" name="John K. Ousterhout ">

WWW book information:
<htmlurl url="http://cseng.aw.com/bookdetail.qry?ISBN=0&percnt;2D201&percnt;2D63337&percnt;2DX&amp;ptype=0" name="cseng.aw.com/bookdetail.qry?ISBN=0&percnt;2D201&percnt;2D63337&percnt;2DX&amp;ptype=0">

Book's examples:
<url url="ftp://ftp.scriptics.com/pub/tcl/doc/book.examples.Z" name="ftp.script
ics.com/pub/tcl/doc/book.examples.Z">

Book suppliment:
<url url="http://www.scriptics.com/doc/tk4.0.ps" name="www.scriptics.com/doc/tk
4.0.ps">

The book primarily covers Tcl 7.3 and Tk 3.6.
<sect2>Practical Programming in Tcl and Tk, II ed.
<p>

Author: <url url="mailto:welch@acm.org" name="Brent Welch">

WWW book information:
<url url="http://www.beedub.com/book/" name="www.beedub.com/book/">

Book's table of contents:
<url url="http://www.beedub.com/book/" name="www.beedub.com/book/">

Book promotion info at section_50000.html of the URL
<url url="http://www.borders.com/sections/" name="www.borders.com/sections/">

This updated edition describes Tcl / Tk 8.0 as it was during the beta period.
 Along with the material from the first edition, it also covers sockets, packag
es,
 namespaces, a great section describing the changes in Tcl 7.4, 7.5, 7.6, and
 8.0 (and Tk as well), Safe Tk and the Plugin!
<sect2>Tcl and Tk Reference Manual
<p>

Editors: Donald Barnes,
<url url="mailto:marc@redhat.com" name="Marc Ewing">, Erik Troan

WWW book information:
<url url="http://www.lsl.com/catalog/books/tcltk/" name="www.lsl.com/catalog/bo
oks/tcltk/">
<sect2>The Visual TCL Handbook, 1/e
<p>

Author: <url url="mailto:david@inforef.com" name="David Young">

WWW book information:
<url url="http://www.amazon.com/exec/obidos/ISBN=013461674X/u/7141-5908756-1074
81" name="www.amazon.com/exec/obidos/ISBN=013461674X/u/7141-5908756-107481">

A comprehensive guide to Visual TCL. This book leads reader from basic
 graphical user interface development concepts to meaningful application develo
pment.
 The book focuses on the TCLX and VT extensions, addressing many fundamental
 TCL topics. VT is a Motif based graphical interface, incompatible with Tk.
 The entire TCL language is documented in a separate Commands section. Comes
 with a CD-ROM that includes SGI, Solaris, HP-UX, AIX and Unixware versions
 of Visual Tcl.
<sect2>Running LINUX
<p>

Author: Matt Welsh and Lar Kaufman

WWW book information:
<url url="http://www.ora.com/catalog/runux2/noframes.html" name="www.ora.com/ca
talog/runux2/noframes.html">

Running Linux is a really well written basic book. It has a chapter on
 programming using Tcl/Tk. (and Perl, C, C++).
<sect2>Tcl/Tk for Dummies (For Dummies)
<p>

Author: Timothy Webster, with Alex Francis

WWW book information:
<url url="http://www.dummies.com/" name="www.dummies.com/">

Another one of the series of the paperback programming books. This one
 focuses on the Tcl plugin as a programming environment.
<sect2>Interactive Web Applications With Tcl/Tk
<p>

Authors: Michael Doyle Hattie Schroeder

WWW book information:
<url url=" http://www.eolas.com/tcl/" name="www.eolas.com/tcl/">

This is a learning by example book, for people who know a bit of programming,
 but are not experts. It covers developing applets as well as stand-alone appli
cations
 and simple server applications. The book comes with the Spynergy toolkit, whic
h
 adds a variety of pure Tcl/Tk procedures for distributed processing, URL retri
eval,
 HTML rendering, database management and platform independent file managment,
 Ed, a Tcl editor and testing environment, an image conversion tool, a demo
 of Tk features, a client/server version of a rolodex application, a pure Tcl
 web server, a client/server push application, a tcl web browser,
<sect1>Manual and On-line Tutorials
<p>
<itemize>
<item>John Ousterhout has written an engineering style guide that describes the
 coding, documentation, and testing conventions that will be used at Sun in
 the coding of the C code in the Tcl core and has made it available to other
 Tcl and Tk developers. It is located at
<url url="ftp://ftp.scriptics.com/pub/tcl/doc/engManual.tar.Z" name="ftp.script
ics.com/pub/tcl/doc/engManual.tar.Z">
<item>A second style guide, covering the writing of Tcl scripts, can be found
 at
<url url="ftp://ftp.scriptics.com/pub/tcl/docs/styleGuide.tar.gz" name="ftp.scr
iptics.com/pub/tcl/docs/styleGuide.tar.gz">.
 Other versions of it can be found at
<url url="http://sunscript.sun.com/techcorner/styleGuide.ps" name="sunscript.su
n.com/techcorner/styleGuide.ps">.
<item>
<url url="http://http2.brunel.ac.uk:8080/&tilde;csstddm/TCL2/TCL2.html" name="A
 brief introduction to TCL/TK ">by
 <url url=" mailto:csstddm@brunel.ac.uk" name="David Martland ">
<item>Another tutorial untitled
<url url="http://www.scism.sbu.ac.uk/tkteach/" name="User interfaces with Tcl/T
k">was
 written by <url url="mailto:fintan@sbu.ac.uk" name="Fintan Culwin ">.
<item>Although you should have your Tcl/Tk manual pages on your system, here's
 another place where to look for
<url url="http://cuiwww.unige.ch/eao/www/TclTkMan/Man.html" name="TCL Manual Pa
ges (from TCL7.4)-Tk Manual Pages (from TK4.0)">.
<item>
<url url="http://www.cis.rl.ac.uk/proj/TclTk/" name="The Tcl/Tk Cookbook"> offe
rs
 a lot of getting-started information.
</itemize>
<sect1>World Wide Web sites
<p>

There are a great number of WWW resources which provide additional information
 about many aspects of Tcl and its extensions.
<itemize>
<item>Refer to
<url url="http://www.tclfaq.wservice.com/tcl-faq/part2.html" name="Tcl-FAQs (pa
rt2)">
 for a great number of pointers to Tcl/Tk documentation and web sites.
<item>Point your web browser at
<url url="http://www.tcltk.com" name="Tcl/Tk Information"> : a site with many
 links to TclTk resources on the web (Information, Extensions, Tools, Training
 and Events).
<item>Point your Web browser at
<url url="http://www.NeoSoft.com/tcl/" name="The Official Contributed Sources A
rchive">
 for the Tool Command Language (Tcl) and the Tk Toolkit, hosted by NeoSoft,
 Inc.
<item><label id="prosandcons">For a discussion dealing with the pros and cons
 of the major scripting languages :
<url url="http://www.sun.com/sunworldonline/swol-10-1997/swol-10-scripting.html
" name="article in SunWorld">
 by <url url=" mailto:claird@Starbase.NeoSoft.com" name="Cameron Laird ">
<item>A web page that contains a variety of comparisons between Tcl/Tk and othe
r
 similar systems. Most of them are taken from "comp.lang.tcl", the author would
 be happy to add any other important article that you folks want to send to
 him.: <url url="http://icemcfd.com/tcl/comparison.html" name="Comparison">
 by <url url="mailto:wayne@icemcfd.com" name="Wayne Christopher">.
<item>
<url url="http://herzberg.ca.sandia.gov/TclCourse/" name="E.J. Friedman-Hill's
Tcl/Tk Course">:
 this document is available only in PowerPoint source form and in low-quality
 HTML form (in HTML format all the figures and some of the text is missing).
</itemize>
<sect1>Other documents &amp; Frequently Asked Questions
<p>

A lot of material is available on the Internet: introductory papers, white
 papers, tutorials, slides, postscript versions of published books in draft
 and many more.

For a complete reference please give a look at the excellent
<url url="http://www.tclfaq.wservice.com/tcl-faq/" name="Tcl-FAQs"> .
<sect1>Newsgroup
<p>

<url url="news:comp.lang.tcl" name="comp.lang.tcl"> is an unmoderated Usenet
 newsgroup, created for the discussion of the Tcl programming language and tool
s
 that use some form of Tcl, such as the Tk toolkit for the X window system,
 Extended Tcl, and expect.

For Tcl/Tk related announcements always refer to
<url url="news:comp.lang.tcl.announce" name="comp.lang.tcl.announce"> : you
 will find release announcement, patches, new application and so on.

Again, faq could be retrieved at
<url url="http://www.tclfaq.wservice.com/tcl-faq/" name="Tcl-FAQs">.
<sect>Tcl/Tk License Terms<label id="license">
<p>

The following terms apply to the all versions of the core Tcl/Tk releases,
 the Tcl/Tk browser plug-in version 2.0, and TclBlend and Jacl version 1.0.
 Please note that the TclPro tools are under a different license agreement.
 This agreement is part of the standard Tcl/Tk distribution as the file named
 "license.terms".

TCL/TK LICENSE TERMS

This software is copyrighted by the Regents of the University of California,
 Sun Microsystems, Inc., Scriptics Corporation, and other parties. The followin
g
 terms apply to all files associated with the software unless explicitly discla
imed
 in individual files.

The authors hereby grant permission to use, copy, modify, distribute, and
 license this software and its documentation for any purpose, provided that
 existing copyright notices are retained in all copies and that this notice
 is included verbatim in any distributions. No written agreement, license, or
 royalty fee is required for any of the authorized uses. Modifications to this
 software may be copyrighted by their authors and need not follow the licensing
 terms described here, provided that the new terms are clearly indicated on
 the first page of each file where they apply.

IN NO EVENT SHALL THE AUTHORS OR DISTRIBUTORS BE LIABLE TO ANY PARTY FOR
 DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES ARISING OUT
 OF THE USE OF THIS SOFTWARE, ITS DOCUMENTATION, OR ANY DERIVATIVES THEREOF,
 EVEN IF THE AUTHORS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

THE AUTHORS AND DISTRIBUTORS SPECIFICALLY DISCLAIM ANY WARRANTIES, INCLUDING,
 BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR
 A PARTICULAR PURPOSE, AND NON-INFRINGEMENT. THIS SOFTWARE IS PROVIDED ON AN
 "AS IS" BASIS, AND THE AUTHORS AND DISTRIBUTORS HAVE NO OBLIGATION TO PROVIDE
 MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.

GOVERNMENT USE: If you are acquiring this software on behalf of the U.S.
 government, the Government shall have only "Restricted Rights" in the software
 and related documentation as defined in the Federal Acquisition Regulations
 (FARs) in Clause 52.227.19 (c) (2). If you are acquiring the software on behal
f
 of the Department of Defense, the software shall be classified as "Commercial
 Computer Software" and the Government shall have only "Restricted Rights" as
 defined in Clause 252.227-7013 (c) (1) of DFARs. Notwithstanding the foregoing
,
 the authors grant the U.S. Government and others acting in its behalf permissi
on
 to use and distribute the software in accordance with the terms specified in
 this license.

</article>