Dont know about tru64 unix
but if I had to do it, I would do one of the following
1. Read the information from the /proc files
2. find the man pages of the commands corresponding to the system call
eg, if ps is the command, in its man pages, it says that ps uses certain files. Also the see also section of the man page tells me to see for sysconf (HP-UX), so now I have got the library which I can use to simulate the ps command
Further the See also section of the sysconf has a tressure for me.
However, some one else might certainly have a better approach.