http://purl.org/tcl/home/man/tcl8.4/TkCmd/console.htm
It is my understanding that, for some strange reason, Tk does not yet support console on Unix. That seems very anti-Tk to me - why waste so much time being cross platform and then break it by not offering something so simple?
RS I think it was the other way round: on Unixes, where Tcl originated, you'd start wish at a console and be able to use its stdin/out/err from inside Tcl. Windows apps typically don't have these channels, so the Windows wish console was added to compensate for the loss. That WinTk's console grew more powerful (e.g. you can interact with the interpreter while a script is running, which you can't by default on Unix) justifies your wish to re-implant the original "bugfix" into generic Tk - or pull tkcon into the core?
Tk syntax help - Arts and crafts of Tcl-Tk programming - Category Command