Andy Millar

disown [-ar] [-h] [jobspec ...]
  Without options, each jobspec is removed from the table
  of active jobs. If jobspec is not present, and neither
  -a nor -r is supplied, the shell's notion of the
  current job is used.  If the -h option is given,  each
  job-spec is not removed from the table, but is marked
  so that SIGHUP is not sent to the job if the shell 
  receives a SIGHUP.  If no jobspec is present, and neither
  the -a nor the -r option is supplied, the current job is
  used. If no jobspec is supplied, the -a option means to
  remove or mark all jobs; the -r option without a jobspec
  argument restricts operation to running jobs.  The
  return value is 0 unless a jobspec does not specify a 
  valid job.