command-line API for manipulation of solution files

I want to write a command line tool for manipulating solution files.  Is there an API for this purpose? The command-line tool itself doesn't matter (perl, python, etc.), I can pick whichever is compatible with available API .  Or, related question, can Visual Studio commands be executed somehow without opening the IDE? 

The use case is, I occasionally have to deal with solution files with 100s of projects in it, and opening Visual Studio is very time consuming. I know how to build from the command-line (via devenv), but occasionally I need to:

1. disable certain projects
2. remove or add new projects
3. adjust project dependencies
4. adjust build mode (solution default, or project specific), Release, Debug etc.

Thanks