PL/SQL file I/O HELP

 Hi there:

        I came cross one problem using fopen procedure within oracle PL/SQL UTL_FILE package. I kept getting exception indicating invalid path. I'm accessing the ORACLE server through a UNIX machine. Does anyone can give me some suggestion on this. THANKS a lot. The followig is the procedure I used to open a file:
 UTL_FILE.FOPEN('dir path', 'filename' 'r');

--
========================================================================
Weixing Chen
c581534_at_showme.missouri.edu
Weixing_Chen_at_muccmail.missouri.edu
=======================================================================