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

File handling

Now that we can open, read, write, and close a file, it is time to put this knowledge to work in a real world manner. We will now create a Tcl script that accesses a file, reorders the stored data, and then outputs it to a secondary file. This is similar to a file handling procedure used to clean up user supplied files.

Getting ready

Using the text editor of your choice create a text file containing the following text:


Save the file in your working directory as input.txt.

How to do it…

Using the text editor of your choice create the following Tcl script and save it in your working directory as filehandler.tcl.

# Check that a filename was provided
if { $argc>0 & $argv>0} {
# Assign the filename to a variable
set fname [lindex $argv 0]
# Open the file for read-only access
set fp [open $fname r]
# Read the contents of the file into a variable
set data [read $fp]
#Close the input file
close $fp
# Split the data and create a Tcl list
set input [split $data...