where are the function definitions to the ansi c library on linux?

Where are functions in ANSI C such as strlen() or getchar() defined on a linux system? You are able to look through the header files but there's no definitions. Sometimes you see a declaration. I think someone told me a while back they are in shared object files *.so files in /usr/lib/. If this is correct, I was wondering how someone would make a shared object file like someone did in libpcap or libdnet? Thanks in advance.

To get the source code for standard library functions like strlen, try
http://www.gnu.org/software/libc/libc.html

As for other packages, maybe try the home page of where the package originates, or perhaps sourceforge?

In either case, someone else compiles the source code down to a set of library files, and then these library files are distributed.