[adunsmoor]

Tcl and the Tk Toolkit by J. Osterhout is an old reference but very useful for getting started with the C API to Tcl including embedding an interpreter. The last 1/3rd of the book is on writing Tcl applications in C.

Also look at the the source files for the Tcl (tclsh) or Tk (wish) shells. They are fairly concise.

[davidw]

There is also an updated version out (with my name on the cover, to boot:-)

http://amzn.to/1LQrLTK

Although even that is not super recent.

Tcl's C API is very pleasant to work with, and its C code is a good read - except for the regex stuff, which are the first few files you'd see in an alphabetical listing.

[mzs]

Yep that was the book I was lent.