DECLARE
  ex           BOOLEAN;
  file_length  NUMBER;
  blsize       NUMBER;
  date_convert char(250);
  test         char(250);
BEGIN
  date_convert := 'ABC_TEST_' ||
                  to_char(sysdate - 1, '""YYYY-""MM-""DD".csv"');
  test         := 'ABC_TEST_2006-01-11.csv';
  DBMS_OUTPUT.PUT_LINE(date_convert); --shows filename
  DBMS_OUTPUT.PUT_LINE(test); --shows filename
  utl_file.fgetattr('ETL_FOLDER1',
                    date_convert,
                    ex,
                    file_length,
                    blsize);
  IF ex THEN
    dbms_output.put_line('File Exists');
  ELSE
    dbms_output.put_line('File Does Not Exist');
  END IF;
  dbms_output.put_line('File Length: ' || TO_CHAR(file_length));
  dbms_output.put_line('Block Size: ' || TO_CHAR(blsize));
END;
/

date_convert char(250);

sql>declare 
  2    v_filename  char(30) := 'test.txt'; 
  3    f  utl_file.file_type; 
  4  begin 
  5    f := utl_file.fopen('FILES', v_filename, 'r'); 
  6    utl_file.fclose(f); 
  7  end;
  8  /
declare
*
ERROR at line 1:
ORA-29283: invalid file operation
ORA-06512: at "SYS.UTL_FILE", line 449
ORA-29283: invalid file operation
ORA-06512: at line 5

sql>declare 
  2    v_filename  varchar2(30) := 'test.txt'; 
  3    f  utl_file.file_type; 
  4  begin 
  5    f := utl_file.fopen('FILES', v_filename, 'r'); 
  6    utl_file.fclose(f); 
  7  end;
  8  /

PL/SQL procedure successfully completed.