8.1. Static Libraries Static libraries are simply collections of object files arranged by the ar (archiver) utility. ar collects object files into one archive file and adds a table that tells which object files in the archive define what symbols. The linker, ld, then binds references to a symbol in one object file to the definition of that symbol in an object file in the archive. Static libraries use the suffix .a. You can convert a group of object files into a static library with a command like ar rcs libname.a foo.o bar.o baz.o
You can also add one object file at a time to an existing archive. ar rcs libname.a foo.o ar rcs libname.a bar.o ar rcs libname.a baz.o
In either case, libname.a will be the same. The options used here are: r | Includes the object files in the library, replacing any object files already in the archive that have the same names. | c | Silently create the library if it does not already exist. | s | Maintain the table mapping symbol names to object file names. |
There is rarely any need to use other options when building static libraries. However, ar has other options and other capabilities; the ar man page describes them in detail. | 
