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<module> defines the include (.h) and library (.a and .so) search directories.  "include" and "lib/<arch>" are appended to what this macro is defined to be.  Yes, this is confusing.

EPICS_BASE defines the version of the EPICS base library behind the directory $EPICS_SITE_TOP/base you want to link your application with.

Application

src Directory

If you're building an app (not a module, not a library), your app will have a Makefile in its src directory.

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