Question

trying to check whether the file I want to read exists or not.

Answer 1

Here are another approaches:

1. Using BFILE and fileexists function of dbms_lob package:

   create or replace function FileExists(
      p_DirName in varchar2,     -- schema object name
      p_FileName in varchar2
    ) return number
   is
     l_file_loc bfile;
   begin
     l_file_loc := bfilename(upper(p_DirName), p_FileName);
     return dbms_lob.fileexists(l_file_loc);  -- 1 exists; 0 - not exists
   end;
   

2. Using fgetattr function of utl_file package:

   create or replace function FileExists(
     p_DirName in varchar2,     -- schema object name
     p_FileName in varchar2
   ) return number
   is
     l_fexists boolean;
     l_flen   number;
     l_bsize  number;
     l_res    number(1);
   begin
     l_res := 0;
     utl_file.fgetattr(upper(p_DirName), p_FileName, l_fexists, l_flen, l_bsize);
     if l_fexists
     then
       l_res := 1;
     end if;  
     return l_res;
   end;