Tcl/Tk quick start - Free

Presented by developerWorks, your source for great tutorials
ibm.com/developerWorks
Section 3. The Tcl language
What makes Tcl tick?
In the following listing, you'll find a common first
example program, as implemented in Tcl. This is a
complete script: the first line invokes the tclsh
environment, and the second does the actual work.
Create the script with a text editor of your
choosing, make it executable by typing chmod +x
hello.tcl, then execute it to test your
handiwork.
~/tcltk$ cat hello.tcl
#!/usr/bin/tclsh
puts stdout {Hello, World!}
~/tcltk$ ./hello.tcl
Hello, World!
Tcl and Tk are interpreted, extensible scripting
languages. The license, which is very similar to the
BSD license, permits free use under any
circumstances, as long as the copyright is retained
in all copies and notices pass verbatim in any
distribution. The license terms make Tcl/Tk free
software.
Tcl/Tk is an interpreted environment. The Tcl
interpreter can be extended by adding
pre-compiled C functions, which can be called from
within the Tcl environment. These extensions can
be custom for a specific purpose, or generic and
widely useful. We'll look at a number of extensions
later in the tutorial, with special attention given to
the first extension, the very popular Expect.
In next few panels, we'll review the major features
of the Tcl language, from metacharacters and
global variables, to operators, mathematical
functions, and core commands. After all, the
Tcl/Tk quick start Page 4 of 29