Forward

 

Tcl is a scripting language something like Perl but extensible and somewhat cleaner. Many extensions are available. Tk is an extension developed by the creator of Tcl and used for creating scripts that interact with users through windows. Tcl can act as a Unix shell and Tk was originally developed to create windows for the X Windows environment. Tcl was meant to be portable and Tcl/Tk has been ported to versions of Microsoft Windows and to the MacIntosh.

Some advantages of Tcl:

• Tcl/Tk runs in essentially the same form on Windows, MacIntosh, and X Windows (Unix) platforms. With version 8.0, the same script will produce menus that are native to the platform on which the script runs.

• Tcl/Tk runs as a plugin from web browsers made by Netscape and Microsoft. It provides a very flexible mechanism for creating a unique security policy to fit unique intranet and extranet needs.

• Tcl/Tk is flexible and interpreted. You can tweak it to do what you want. You can write tools to help you with repetitive programming tasks.

• Tcl/Tk is extensible. You can add language features that support the kinds of programming you must do.

• You can use Tcl/Tk for fast high-level scripting that reuses code written in C/C++.

• Although Tcl/Tk has a strong C/C++ connection, you can use Tcl/Tk without knowing any C/C++.

• Tcl is a scripting language for running other programs.

• Tk's GUI environment has been adopted into other languages, notably Perl and Python. Using it from Tcl keeps you up-to-date with its changes.

• Tcl is the basis for Expect which is a useful language for controlling interactive applications.

This book is aimed at programmers who want to learn Tcl/Tk because they find these advantages attractive. It is a self-teaching book with more than 200 solved exercises. All exercises run on both Windows and Unix versions of Tcl/Tk. Only a couple require code variations to accomplish this. The material in this book comes close to being platform independent.

Programmers and systems administrators with other interests may wish to learn from this book as well:

• Tcl/Tk is valuable to Unix systems administrators who want to provide their users with scripts accessible through a GUI front end. (The examples in this book do not illustrate systems administration topics because these tend to vary with the platform.)

• Tcl/Tk is valuable to C/C++ programmers who want to learn a high-level scripting language for their user interfaces or for integrating pieces of a large system.

Although this book is meant to be studied sequentially by someone who works on the exercises, it can serve the purpose of an "introductory manual" as well. The index is designed to send you to the main place for any given topic. At that place you find cross references to other places.

The material is detailed but not inclusive. I have been concerned that descriptions not be so long or so detailed that few people would wish to study them and that descriptions not be so short that many people would need to go to another source before accomplishing anything useful.

This book is not a simple-minded introduction, not a comprehensive manual, and not a collection of production-quality scripts. It bridges the gaps between those things.

Here is the background I suggest you will need. My suggestions are based on the assumption that you are studying the material on your own. A good instructor can fill in some gaps so that you could study the material with less preparation.

• Four successful semesters of a solid four year computer science degree or all of any technical bachelor's degree that is combined with a year's experience as a programmer doing a variety of things in a general-purpose language.

• Some experience with the GUI environment that you will be using to run the Tk exercises, for example, with Windows or X Windows. If you only study the Tcl part of the book, this is not needed.

• For Chapters 22, 23, 24, and 25, a basic knowledge of C or C++. You do not need to read these chapters.

• For Chapters 10 and 21, some experience using the world-wide web. You need not read these chapters.

Ways to write maintainable, reusable code have long been an interest of mine. You will see this interest reflected in the way I have solved some of the exercises.