Secrets in This Chapter
Using Control-Flow Commands in Tcl
Using the switch Command
Writing Tcl Procedures
Manipulating Strings in Tcl
Accessing Environment Variables in Tcl
Performing File Operations in Tcl
Executing Linux Commands in Tcl
Learning Tk Widget Basics
Defining Widget Hierarchies in Tk
Binding Actions to Events
Understanding Keyboard Events
Understanding Mouse Events
If you are already a C and X Window system programmer, you will be surprised by the ease with which you can create graphical applications with Tcl (Tool Command Language) and its associated X toolkit, Tk-collectively referred to as Tcl/Tk (pronounced 'tickle/tee kay'). Tcl is a scripting language like Perl. The biggest strength of Tcl is its X toolkit, Tk, which enables you to develop scripts with GUIs.
When I started using Tcl/Tk, I was pleasantly surprised by how few lines of Tcl/Tk it takes to create a functioning graphical interface. To a newcomer, a Tcl/Tk script still looks rather complicated, but if you have used C-based toolkits, such as Xt and Motif, to write programs, you can appreciate the high-level abstractions of Tk. Creating a user-interface component such as a button is much simpler in Tk than in Motif. In Tk, you still have to tend to many details, such as how to lay out the components of the user interface, but you can see results faster than you can with a C program that calls the Motif library.
If you have never programmed, don't avoid this chapter out of fear. The examples in this chapter teach you the basics of Tcl and Tk. You are bound to become a believer in Tcl/Tk after you see how quickly you can use Tcl/Tk's interpreter to create applications with graphical interfaces.