Extended Tcl has:
The following variables are set and/or used by the Tcl shell.
argv0
Contains the name of the Tcl program specified on the com-
mand line or the name that the Tcl shell was invoked under
if no program was specified. argc Contains a count of the
number of argv arguments (0 if none). argv A list contain-
ing the arguments passed in from the command line, excluding
arguments used by the Tcl shell. The first element is the
first passed argument, not the program name.
tcl_interactive
Set to 1 if Tcl shell is invoked interactively, or 0 if the
Tcl shell is directly executing a script. Normally checked
by scripts so that they can function as a standalone appli-
cation if specified on the command line, but merely load in
and not execute if loaded during an interactive invocation
of Tcl.
auto_path
Path to search to locate Tcl autoload libraries. Used by
the both the Tcl and TclX library autoloading facility.
tclx_library
Path to the TclX runtime library. If your running the TclX
shell or an application based on it (like wishx). The TclX
initialization file normally adds this to the auto_path.
tkx_library
Path to the TkX runtime library. This is set only if your
application has called Tkx_Init. The TkX initialization
file normally adds this to the auto_path.
tcl_prompt1
Contains code to run to output the prompt used when interac-
tively prompting for commands.
tcl_prompt2
Contains code to run to output the prompt used when interac-
tively prompting for continuation of an incomplete command.
TCLXENV
Array that contains information used internally by various
Tcl procedures that are part of the TclX shell.