When you have installed Tcl, the program you will then call to
utilize it is tclsh. For instance,
if you write some code to a file "hello.tcl", and you want to
execute it, you would do it like so: tclsh hello.tcl.
Depending on the version of Tcl installed, and the operating system
distribution you use, the tclsh program may
be a link to the real executable, which may be named tclsh8.6 or tclsh86.exe on Microsoft Windows.
The tclsh is a simple command-line
interactive interpreter. You can either start it with a script on the
command line, in which case it runs the script to completion and then
exits, or you can start it without any arguments, in which case you will
be presented with an interactive prompt, usually using a %
symbol to prompt for input. In interactive mode, you can type in commands,
which Tcl will then execute and display the result, or any error messages
that result. To exit the interpreter, type exit and press Return. Playing around with the
interactive interpreter is a great way to learn how to use Tcl. Most Tcl
commands will produce a helpful error message explaining how they are used
if you just type in the command with no arguments. You can get a list of
all the commands that your interpreter knows about by typing info
commands.
The tclsh executable is just one way of
starting a Tcl interpreter. Another common executable, which may be
installed on your system, is the wish, or
WIndowing SHell. This is a version of Tcl that automatically loads the Tk
extension for building graphical user interfaces (GUIs). This tutorial does
not cover Tk, and so we will not use the wish
interpreter here. Other options are also available, providing more
functional environments for developing and debugging code than that provided
by the standard tclsh. One very popular choice
is the TkCon enhanced
interpreter, written by Jeff Hobbs. The Eclipse IDE offers good Tcl support,
in the form of the DLTK
extension, and the Tcl'ers Wiki offers a
list of IDEs with Tcl support and a comprehensive catalogue of Tcl source code editors.
Don't panic, though! If you don't know how to use a sophisticated
development environment, it is still very easy to write Tcl code by hand in
a simple text editor (such as Notepad).