DBMS_SESSION.SESSION_TRACE_ENABLE(TRUE,TRUE,'ALL_EXECUTIONS');
alter session set events '10046 trace name context forever, level 12';
-- invoke the SQL code
DBMS_SESSION.SESSION_TRACE_ENABLE(FALSE,FALSE,NULL);
DBMS_MONITOR.SESSION_TRACE_ENABLE(
    session_id   IN  BINARY_INTEGER DEFAULT NULL,
    serial_num   IN  BINARY_INTEGER DEFAULT NULL,
    waits        IN  BOOLEAN DEFAULT TRUE,
    binds        IN  BOOLEAN DEFAULT FALSE,
    plan_stat    IN  VARCHAR2 DEFAULT NULL);
Oracle recommends that you use the DBMS_MONITOR and DBMS_SESSION packages instead. 
SQL_TRACE is retained for backward compatibility only.

bcm@bcm-laptop:~$ tkprof
Usage: tkprof tracefile outputfile [explain= ] [table= ]
              [print= ] [insert= ] [sys= ] [sort= ]
  table=schema.tablename   Use 'schema.tablename' with 'explain=' option.
  explain=user/password    Connect to ORACLE and issue EXPLAIN PLAN.
  print=integer    List only the first 'integer' SQL statements.
  aggregate=yes|no
  insert=filename  List SQL statements and data inside INSERT statements.
  sys=no           TKPROF does not list SQL statements run as user SYS.
  record=filename  Record non-recursive statements found in the trace file.
  waits=yes|no     Record summary for any wait events found in the trace file.
  sort=option      Set of zero or more of the following sort options:
    prscnt  number of times parse was called
    prscpu  cpu time parsing
    prsela  elapsed time parsing
    prsdsk  number of disk reads during parse
    prsqry  number of buffers for consistent read during parse
    prscu   number of buffers for current read during parse
    prsmis  number of misses in library cache during parse
    execnt  number of execute was called
    execpu  cpu time spent executing
    exeela  elapsed time executing
    exedsk  number of disk reads during execute
    exeqry  number of buffers for consistent read during execute
    execu   number of buffers for current read during execute
    exerow  number of rows processed during execute
    exemis  number of library cache misses during execute
    fchcnt  number of times fetch was called
    fchcpu  cpu time spent fetching
    fchela  elapsed time fetching
    fchdsk  number of disk reads during fetch
    fchqry  number of buffers for consistent read during fetch
    fchcu   number of buffers for current read during fetch
    fchrow  number of rows fetched
    userid  userid of user that parsed the cursor

--
set pages 1000
--
set tim on
--
-- Test how long a query takes.
--
exec dbms_session.session_trace_enable(true,true,'ALL_EXECUTIONS');
--
alter session set events '10046 trace name context forever, level 12';
--
-- invoke the SQL code
--
select * from all_tables where owner = 'my_user';
--
exec dbms_session.session_trace_enable(false,false,null);
--
exec DBMS_MONITOR.SESSION_TRACE_ENABLE;
--