appending to files in lisp?

[Wilson.Harvey@CMU-CS-IUS]

Does anyone have a function that will allow them to append to a file?  I
need to open a file and write some data to it then, at a later time, reopen
the same file and add some more data to it.  The only things that I could
find in Franz were "infile" and "outfile", and "outfile" truncates the file
when called.  It would be nice if the function would create the file if it
didn't already exist, but that is not necessary.

Thanks. --Wilson

P.S. I tried writing a C-function to handle this, but I didn't have any luck
passing the FILE pointer back into Franz.  It didn't recognize the pointer
as a port, and I don't know how to set it straight.