Book Image

Tcl/Tk 8.5 Programming Cookbook

Book Image

Tcl/Tk 8.5 Programming Cookbook

Overview of this book

With Tcl/Tk, you can create full-featured cross-platform applications in a simple and easy-to-understand way without any expensive development package; the only tools required are a simple text editor and your imagination. This practical cookbook will help you to efficiently interact with editors, debuggers, and shell type interactive programs using Tcl/Tk 8. This cookbook will comprehensively guide you through practical implementation of Tcl/Tk 8.5 commands and tools. This book will take you through all the steps needed to become a productive programmer in Tcl/Tk 8. Right from guiding you through the basics to creating a stand-alone application, it provides complete explanation of all the steps along with handy tips and tricks. The book begins with an introduction to the Tcl shell, syntax, variables, and programming best practices in the language. It then explores procedures and the flow of events with control constructs followed by advanced error trapping and recovery. From Chapter 4, a detailed study of string expressions and handling enables you to handle various string functions and use lists to expand the string functionality. The book then discusses in-depth the Tcl Dictionary and how to utilize it to store and retrieve data. File operations and Tk GUI handling are covered extensively along with a developing a real-world address book application to practice the concepts learned.
Table of Contents (20 chapters)
Tcl/Tk 8.5 Programming Cookbook
About the Author
About the Reviewers

Determining the size of a string

The size of a string can be an invaluable piece of information. Imagine if you will, loading data to a database where the field sizes are fixed at 25 characters. Trying to load a string of 50 characters into a field designed for 25 will, at best, result in a truncation of the data. Keep in mind that the byte-length of a string may be greater if multibyte characters exist. To assist us in this, Tcl has provided the length keyword.

The syntax of the string command is as follows:

string length string

The only values passed to the string command in this instance are the length keyword and the string to be checked.

How to do it…

In the following example, we will determine the length of a character string that contains whitespace, as you might encounter in the database scenario I mentioned earlier. The return value from the command is provided for clarity. Enter the following command:

% string length "123 Any Street"

How it works…

As you can see, the command has...