Map Oracle session to OS process ID

A query to view OS process IDs corresponding to Oracle sessions:

SELECT
  p.spid,
  s.sid,
  s.username,
  s.machine,
  s.osuser,
  s.program,
  s.status,
  s.module,
  s.client_info
FROM
  v$session s,
  v$process p
WHERE
  s.paddr = p.addr
ORDER BY
  7, 4, 5;

The first column is the process ID on the database server operating system.