Files related....

fuser: Identifies processes using a file or file structure
whodo: Lists the jobs being performed by users on the system.
procfiles:list symbols from object files

ar: list library contents (.a)
nm: list symbols from object files (.a, .so, .o)
ldd: Lists dynamic dependencies (XCOFF) ($LD_LIBRARY_PATH)
what: Displays identifying information in files. (.a, .so, .o, XCOFF), work with GET/SCCS