TclSpice brings NGspice simulation engine into your Tcl-scripts. All spice directives are available as Tcl functions and it features some new commands that are useful for the integration into the Tcl environment. It includes XSpice. GUI is handled by Tk using BLT vectors.
NGspice is a mixed-level/mixed-signal circuit simulator. Its code is based on three open source software packages: Spice3f5, Cider1b1 and Xspice. . NGspice is part of gEDA project, a full GPL'd suite of Electronic Design Automation tools.