How to redirect the output of DBMS_OUTPUT.PUT_LINE to a file?

Question

I need to debug in pl/sql to figure times of procedures, I want to use:

SELECT systimestamp FROM dual INTO time_db;
DBMS_OUTPUT.PUT_LINE('time before procedure ' || time_db);

but I don't understand where the output goes to and how can I redirect it to a log file that will contain all the data I want to collect?

Answer 1

DBMS_OUTPUT is not the best tool to debug, since most environments don't use it natively. If you want to capture the output of DBMS_OUTPUT however, you would simply use the DBMS_OUTPUT.get_line procedure.

Here is a small example:

SQL> create directory tmp as '/tmp/';

Directory created

SQL> CREATE OR REPLACE PROCEDURE write_log AS
  2     l_line VARCHAR2(255);
  3     l_done NUMBER;
  4     l_file utl_file.file_type;
  5  BEGIN
  6     l_file := utl_file.fopen('TMP', 'foo.log', 'A');
  7     LOOP
  8        EXIT WHEN l_done = 1;
  9        dbms_output.get_line(l_line, l_done);
 10        utl_file.put_line(l_file, l_line);
 11     END LOOP;
 12     utl_file.fflush(l_file);
 13     utl_file.fclose(l_file);
 14  END write_log;
 15  /

Procedure created

SQL> BEGIN
  2     dbms_output.enable(100000);
  3     -- write something to DBMS_OUTPUT
  4     dbms_output.put_line('this is a test');
  5     -- write the content of the buffer to a file
  6     write_log;
  7  END;
  8  /

PL/SQL procedure successfully completed

SQL> host cat /tmp/foo.log

this is a test