Compile multiple C files with make

Question

(I am running Linux Ubuntu 9.10, so the extension for an executable is executablefile.out) I am just getting into modular programming (programming with multiple files) in C and I want to know how to compile multiple files in a single makefile. For example, what would be the makefile to compile these files: main.c, dbAdapter.c, dbAdapter.h? (By the way, If you haven't figured it out yet, the main function is in main.c) Also could someone post a link to the documentation of a makefile?

Answer 1

The links posted are all good. For you particular case you can try this. Essentially all Makefiles follow this pattern. Everything else is shortcuts and macros.

program: main.o dbAdapter.o
   gcc -o program main.o dbAdapter.o

main.o: main.c dbAdapter.h
   gcc -c main.c

dbAdapter.o dbAdapter.c dbAdapter.h
   gcc -c dbAdapter.c

The key thing here is that the Makefile looks at rules sequentially and builds as certain items are needed.

It will first look at program and see that to build program, it needs something called main.o and dbAdapter.o.

It will then find main.o. However, to build main.o, it will need main.c and dbAdapter.h (I assume dbAdapter.h is included in main.c).

It will use those sources to build main.o by compiling it using gcc. The -c indicates the we only want to compile.

It does the same thing with dbAdapter.o. When it has those two object files, it is ready to link them. It uses the gcc compiler for this step as well. The -o indicates that we are creating a file called program.