S
sgfc is the reference implementation and gold-standard implementation of the SGF standard for storing records of Go/Baduk games. A command line program written in ANSI C, it allows you to validate and perform simple transformations on SGF files.
A mature stable implementation which has proved vital to the promotion of the SGF standard. A must if you generate, consume or curate SGF files.
The biggest weaknesses are reflections of weaknesses in the underlying standard, particularly with respect to internationalisation.