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
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
