How to get file path when using MOD PLSQL

CREATE OR REPLACE Function GETFILEPATH return varchar2 is
script_name varchar2(255) default owa_util.get_cgi_env(‘SCRIPT_NAME’);
path_info varchar2(255) default owa_util.get_cgi_env(‘PATH_INFO’);
pos number;
BEGIN
script_name := script_name || path_info;
pos := instr(script_name,’docs’);
script_name := substr(script_name,pos+5,length(script_name)-pos-4);
return script_name;
END;
/