How to check if a build is required in Eclipse pre-build script?

I am developing C/C++ code in Eclipse. Does anyone know if there is a way (perhaps some pre-defined variable) that would let me know during the pre-build step (to be passed to a pre-build script) if a build will be required (i.e. if the project has changed)?

I am writing a script to automatically update a version number but only want it to do so if there have been changes.

Thanks!

Solution

You can add a builder which does the task instead of putting it in a pre-build step. This version incrementing builder has its own dependencies (which can be the the complete project or an interface folder if you want to limit the scope of changes) and is thus executed only if there is a demand for a new version.