Tcl Environment

When a Tcl script is started, the standard set of Tcl and, if running with the Tk widgets support, Tk variables is available in the interpreter.

In addition, the toolkit provides access to internal toolkit status information via the global array variable cactvs . It is automatically present both in the top-level interpreter and in slave and thread interpreters. Many of the elements in the array may be modified by script commands. If they are manipulated this way, their effects are immediate, but not persistent, and visible in all interpreters.

In case the current application includes a Python interpreter, it contains an equivalent global dictionary. Changes made in any language to the control variable are visible in the other.

Parameter changes are forgotten the next time the interpreter is executed.