The in-depth version:
We use libraries to organize information, which often simplifies access to that information. The same can be said for C libraries, in which a library could house many small functions and scripts, rather than having a huge collection of files in a directory.
Once the library is built, the program main.o can be compiled to an executable with the following command:
cc main.o -L. -lyourlibraryname -o prog
where -L tells the linker to look for the library in the current directory and where -l indicates that this is the name of the library.
But what about the “ranlib” command?
The ranlib command is used to index the library so that symbol look-up is faster in the library. It’s easier to find a book in a shelf when the collection is in alphabetical order. It’s similar with finding code in a collection of scripts.
Finally, please note that libraries are compiled different on mac laptops with M1 chips.