TclTk-HOWTO

1.  Introduction


  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

  ______________________________________________________________________
  make xconfig
  ______________________________________________________________________



  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 Red Hat Software
  <http://www.redhat.com> - 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.

  1.1.  Purpose of this document


  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
  ``References section'' in order to find where to retri eve specific
  information about Tcl and Tk.

  1.2.  What you should know before reading


  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:

  ·  simple programming concepts;

  ·  using very common unix commands and/or utilities;

  ·  having access to the Internet;

  ·  using ftp.

  1.3.  New versions of this document


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

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

  I will try to incorporate in my Web-Page
  <http://space.tin.it/computer/tlqhr/> 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.

  1.4.  Revision History


  ·  Version 0.1: 28 October 1998 - first version;

  ·  Version 0.2: 07 November 1998 - deep restyling and lifting.

  1.5.  Feedback and other stuff


  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, ( Luca
  Rossetti <mailto:lukaros@tin.it> ), 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.

  1.6.  Credits


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

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

  1.7.  Distribution Policy


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


  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 LDP COPYRIGHT
  <http://sunsite.unc.edu/LDP/LDP-COPYRIGHT.html> .

  Please read the LDP Manifesto <http://sunsite.unc.edu/LDP/LDP-
  Manifesto.html> for more details.

  2.  Tcl/Tk History


  Tcl/Tk originated with Dr. John Ousterhout
  <mailto:ouster@scriptics.com> (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 words at www.scripti
  cs.com/scripting/tclHistory.html
  <http://www.scriptics.com/scripting/tclHistory.html>.

  2.1.  Cronology


  ·  1989: The first external releases of Tcl and beginning of Tk imp
     lemention;

  ·  1991: First release of Tk;

  ·  1994: Dr. Ousterhout was hired by Sun Microsystems, Inc.: he was a
     Distinguished Engineer and led the Tcl project.

  ·  April/May 1997: 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: Su
     nScript-Story .

  ·  August 1997: a Tcl Consortium was formed.

  ·  February 1998: Dr. Ousterhout left Sun to create Scriptics
     <http://www.scriptics.com/>, a company dedicated to scripting
     tools, applications, and services. According to www.scriptics.com
     /about/news/qa.html < http://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.

  ·  April 23, 1998: the Association for Computing Machinery ACM
     <http://www.acm.org/> awarded the 1997 Software System Award to
     John Ousterhout and Scriptics ( www.acm.org/awards/
     <http://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.

  3.  What is Tcl/Tk


  3.1.  What is Tcl?



  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:

  ·  Tcl provides a standard syntax: once users know Tcl, they will be
     able to issue commands easily to any Tcl-based application.

  ·  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.

  ·  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.

  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 www.NeoSoft.com/tcl
  /whatistcl.html <http://www.NeoSoft.com/tcl/whatistcl.html > .



  3.2.  What is Tk?


  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.

  3.3.  Extensions


  Since Tcl is so easy to extend, many try to share extensions,
  including the popular itcl, [incr Tcl] <http://www.tcltk.com/itcl/>,
  ObjectTcl, TclX, Tix  <http://tix.mne.com/>, and BLT
  <http://www.tcltk.com/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 Expect
  <http://expect.nist.gov>.  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 www.scr
  iptics.com/resource/software/extensions/
  <http://www.scriptics.com/resource/software/extensions/>.

  3.4.  Supported Platforms


  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:


  ·  Windows 95

  ·  Windows NT

  ·  Solaris and SunOS

  ·  Linux

  ·  HP-UX

  ·  SGI

  ·  IRIX

  ·  Digital Unix

  ·  AIX

  ·  SCO Unix

  ·  Most other Unix-like operating systems Macintosh (68K and Power
     Mac)

  ·  Pre-compiled releases are available for different Linux
     distribution.

  4.  Installing and getting started with Tcl and Tk


  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 ``license.terms'' section for complete
  information).


  Many more Tcl/Tk scripts and extensions are also available freely.

  4.1.  Downloading the Core Distributions


  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 ftp.scriptics.com/pub/tcl/
  <ftp://ftp.scriptics.com/pub/tcl/>.


  The primary HTTP site is www.scriptics. com/software/download.html
  <http://www.scriptics.com/software/download.html> .

  4.2.  Installation


  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:

  ______________________________________________________________________
  gunzip -c tcl8.0.3.tar.gz
  ______________________________________________________________________



  or

  ______________________________________________________________________
  tar xf - zcat tcl8.0.3.tar.Z
  ______________________________________________________________________



  or

  ______________________________________________________________________
  tar xf - unzip tcl80.3.zip
  ______________________________________________________________________



  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.

  4.3.  The Contributed Archive


  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 ftp.neosoft.com/pub/tcl <ftp://ftp.neosoft.com/pub/tcl>.

  4.4.  Mirror Sites


  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: ftp.scriptics.com/pub/tcl/
  <ftp://ftp.scriptics.com/pub/tcl/> for a list of the mirror sites in
  your country.

  4.5.  Which Releases to Use


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

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

  4.6.  Where to report problems, bugs, or enhancements


  Use comp.lang.tcl < news.comp.lang.tcl> for public communicati ons.

  The alternative would be to send problems, suggestions, new ideas,
  etc.  directly to the author. Email to John Ousterhout
  <mailto:Ouster@scriptics.com> 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
  comp.lang.tcl.announce <news:news.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 comp.lang.tcl.announce
  <news:news.comp.lang.tcl.announce> newsgroup, send email with the
  details to tcl-announce <mailto:tcl-announce@mitchell.org>. Also, feel
  free to just point folk at your own ftp site or WWW site if you have
  one which can be used .

  5.  Just a little bit of Programming


  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:

  ______________________________________________________________________
  wish hello.tcl
  ______________________________________________________________________



  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.)

  5.1.  The one-minute program in Tcl


  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:

  ______________________________________________________________________
  # This is a comment
  button .b -text "Hello World" -command exit
  pack .b
  ______________________________________________________________________



  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:

  ______________________________________________________________________
  #! /usr/local/bin wish -f
  button .b -text "Hello World" -command exit
  pack .b
  ______________________________________________________________________



  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

  ______________________________________________________________________
  chmod 775 Hello
  ______________________________________________________________________



  and run it inside X.

  You will see a button labelled Hello World inside a window: clicking
  it will close (exit) the window.

  6.  Scripting Language: pros and cons


  To understand the importance and the future of Tcl/Tk I strongly
  suggest to point your web browser at the URL www.scriptics
  .com/people/john.ousterhout/
  <http://www.scriptics.com/people/john.ousterhout/> by John K.
  Ousterhout  <mailto:ouster@scriptics.com>. 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 ``the comparison
  discussion''.

  Here's a summary of the most important pros and cons about Tcl/Tk.

  6.1.  Some of the most common complaints about Tcl


  6.1.1.  Tcl is interpreted


  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.

  6.1.2.  Several characteristics are not intuitive


  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.

  6.2.  Some of the most pros about Tcl


  6.2.1.  It is a high-level scripting language


  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.


  6.2.2.  Tcl is free


  You can get the sources for free over the Internet from Scriptics
  Download Page or from the FTP site for Tcl.  The software c ore site
  <http://www.scriptics.com/software/download.html> 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 www.scriptics.com/about/n
  ews/qa.html <www.scriptics.com/about/news/qa.html> .

  6.2.3.  It runs on many platforms


  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.

  6.2.4.  It is interpreted


  You can execute your code directly, without compiling and linking
  (though Tcl compilers are available).

  6.2.5.  It is extensible


  It's easy to add your own commands to extend the Tcl language. You can
  write your commands in C or Tcl.

  6.2.6.  It is embeddable in your applications


  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.

  6.2.7.  Tcl/Tk is Year 2000 (Y2K) compliant


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


  7.  Most Famous Programs using Tcl/Tk


  Apart from the two implementation described in the ``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
  part 4 <http://www.tclfaq.wservice.com/tcl-faq/part4.html> of the
  frequently-asked questions on Tcl/Tk (FAQs). I suggest you to visit

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

  Another good starting point is www.NeoSoft.com/tcl/
  <http://www.NeoSoft.com/tcl/>.

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

  If you're a Tcl/Tk Linux developer, feel free to send me
  <mailto:lukaros@tin.it> a URL (and a description of the work) that I
  can link to in here.

  8.  References


  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.

  8.1.  Books


  Many books concerning Tcl/Tk were written and are to be published. I
  won't even try to list them all (another howto woudn't be enough for
  that : ) ). You can find much more information plus additional notes
  at:

  ·  www.tcltk.com/consortium/resources/books.html

  ·  www.amazon.com/exec/obidos/subst/categories/computer-
     programming/tcl-tk-article/002-8989352-4516417


  ·  Page: tcl_books.html at URL starbase-neosoft-tcl-books

  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.


  8.1.1.  Tcl and the Tk Toolkit


  Author: John K. Ousterhout  <mailto:ouster@scriptics.com>

  WWW book information:
  cseng.aw.com/bookdetail.qry?ISBN=0%2D201%2D63337%2DX&ptype=0

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

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

  The book primarily covers Tcl 7.3 and Tk 3.6.

  8.1.2.  Practical Programming in Tcl and Tk, II ed.


  Author: Brent Welch <mailto:welch@acm.org>

  WWW book information: www.beedub.com/book/
  <http://www.beedub.com/book/>

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

  Book promotion info at section_50000.html of the URL
  www.borders.com/sections/ <http://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!

  8.1.3.  Tcl and Tk Reference Manual


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

  WWW book information: www.lsl.com/catalog/bo oks/tcltk/
  <http://www.lsl.com/catalog/books/tcltk/>

  8.1.4.  The Visual TCL Handbook, 1/e


  Author: David Young <mailto:david@inforef.com>

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

  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.

  8.1.5.  Running LINUX


  Author: Matt Welsh and Lar Kaufman

  WWW book information: www.ora.com/ca talog/runux2/noframes.html
  <http://www.ora.com/catalog/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++).

  8.1.6.  Tcl/Tk for Dummies (For Dummies)


  Author: Timothy Webster, with Alex Francis

  WWW book information: www.dummies.com/ <http://www.dummies.com/>

  Another one of the series of the paperback programming books. This one
  focuses on the Tcl plugin as a programming environment.

  8.1.7.  Interactive Web Applications With Tcl/Tk


  Authors: Michael Doyle Hattie Schroeder

  WWW book information: www.eolas.com/tcl/ < http://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,

  8.2.  Manual and On-line Tutorials


  ·  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 ftp.script ics.com/pub/tcl/doc/engManual.tar.Z
     <ftp://ftp.scriptics.com/pub/tcl/doc/engManual.tar.Z>

  ·  A second style guide, covering the writing of Tcl scripts, can be
     found at ftp.scr iptics.com/pub/tcl/docs/styleGuide.tar.gz
     <ftp://ftp.scriptics.com/pub/tcl/docs/styleGuide.tar.gz>.  Other
     versions of it can be found at sunscript.su
     n.com/techcorner/styleGuide.ps
     <http://sunscript.sun.com/techcorner/styleGuide.ps>.

  ·  A  brief introduction to TCL/TK
     <http://http2.brunel.ac.uk:8080/~csstddm/TCL2/TCL2.html>by David
     Martland  < mailto:csstddm@brunel.ac.uk>


  ·  Another tutorial untitled User interfaces with Tcl/T k
     <http://www.scism.sbu.ac.uk/tkteach/>was written by Fintan Culwin
     <mailto:fintan@sbu.ac.uk>.

  ·  Although you should have your Tcl/Tk manual pages on your system,
     here's another place where to look for TCL Manual Pa ges (from
     TCL7.4)-Tk Manual Pages (from TK4.0)
     <http://cuiwww.unige.ch/eao/www/TclTkMan/Man.html>.

  ·  The Tcl/Tk Cookbook <http://www.cis.rl.ac.uk/proj/TclTk/> offe rs a
     lot of getting-started information.

  8.3.  World Wide Web sites


  There are a great number of WWW resources which provide additional
  information about many aspects of Tcl and its extensions.

  ·  Refer to Tcl-FAQs (pa rt2) <http://www.tclfaq.wservice.com/tcl-
     faq/part2.html> for a great number of pointers to Tcl/Tk
     documentation and web sites.

  ·  Point your web browser at Tcl/Tk Information <http://www.tcltk.com>
     : a site with many links to TclTk resources on the web
     (Information, Extensions, Tools, Training and Events).

  ·  Point your Web browser at The Official Contributed Sources A rchive
     <http://www.NeoSoft.com/tcl/> for the Tool Command Language (Tcl)
     and the Tk Toolkit, hosted by NeoSoft, Inc.

  ·  For a discussion dealing with the pros and cons of the major
     scripting languages : article in SunWorld
     <http://www.sun.com/sunworldonline/swol-10-1997/swol-10-scripting.html
     > by Cameron Laird  < mailto:claird@Starbase.NeoSoft.com>

  ·  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.: Comparison
     <http://icemcfd.com/tcl/comparison.html> by Wayne Christopher
     <mailto:wayne@icemcfd.com>.

  ·  E.J. Friedman-Hill's Tcl/Tk Course
     <http://herzberg.ca.sandia.gov/TclCourse/>: 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).

  8.4.  Other documents & Frequently Asked Questions


  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 Tcl-FAQs
  <http://www.tclfaq.wservice.com/tcl-faq/> .

  8.5.  Newsgroup


  comp.lang.tcl <news: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
  comp.lang.tcl.announce <news:comp.lang.tcl.announce> : you will find
  release announcement, patches, new application and so on.

  Again, faq could be retrieved at Tcl-FAQs
  <http://www.tclfaq.wservice.com/tcl-faq/>.

  9.  Tcl/Tk License Terms


  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.