The C library has exploded. The manual page may give an indication where to find a specific function.
Those libraries are essentially split over two directories:
/usr/lib /usr/ccs/lib.
Important libraries:
/usr/lib: libsocket - socket functions libnsl - network services library
/usr/ccs/lib: libgen - regular expression functions libcurses - the SysVR4 curses/terminfo library.In Solaris 7 the contents of /usr/ccs/lib was moved back to /usr/lib.
See Intro(3) for more details.