Tornado

Tornado 2.0
User’s Guide
5.7 Tcl: Shell Interpretation
The shell has a Tcl interpreter interface as well as the C interpreter interface. This
section illustrates some uses of the shell Tcl interpreter. If you are not familiar with
Tcl, we suggest you skip this section and return to it after you have gotten
acquainted with Tcl. (For an outline of Tcl, see B. Tcl.) In the interim, you can do a
great deal of development work with the shell C interpreter alone.
To toggle between the Tcl interpreter and the C interpreter in the shell, type the
single character ?. The shell prompt changes to remind you of the interpreter state:
the prompt -> indicates the C interpreter is listening, and the prompt tcl> indicates
the Tcl interpreter is listening. 7 For example, in the following interaction we use the
C interpreter to define a variable in the symbol table, then switch into the Tcl
interpreter to define a similar Tcl variable in the shell itself, and finally switch back
to the C interpreter:
-> hello="hi there"
new symbol "hello" added to symbol table.
hello = 0x3616e8: value = 3544824 = 0x3616f8 = hello + 0x10
-> ?
tcl> set hello {hi there}
hi there
tcl> ?
->
If you start windsh from the Windows command line, you can also use the option
-Tclmode (or -T) to start with the Tcl interpreter rather than the C interpreter.
Using the shell’s Tcl interface allows you to extend the shell with your own
procedures, and also provides a set of control structures which you can use
interactively. The Tcl interpreter also acts as a host shell, giving you access to UNIX
command-line utilities on your development host.
For example, you can call stty from the Tcl interpreter to change the special
characters in use—in the following, to specify the quit character as CTRL+B and
verify the new setting (the quit character is normally CTRL+X; when you type it in
the shell, it reboots the target, restarts the target server, and resets all attached
tools):
tcl> stty quit \002
tcl> stty
speed 9600 baud; line = 0;
quit = ^B; eof = ^A; status = ; min = 1; time = 0;
-icanon -echo
7. The examples in this book assume you are using the default shell prompts, but you can
change the C interpreter prompt to whatever string you like using shellPromptSet( ).
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