UNIX for Dummies Questions & Answers

       ulimit [-SHacdflmnpstuv [limit]]
              Provides control over the resources available to the  shell  and
              to  processes started by it, on systems that allow such control.
              The -H and -S options specify that the hard or soft limit is set
              for  the  given resource.  A hard limit cannot be increased once
              it is set; a soft limit may be increased up to the value of  the
              hard  limit.   If  neither -H nor -S is specified, both the soft
              and hard limits are set.  The value of limit can be a number  in
              the unit specified for the resource or one of the special values
              hard, soft, or unlimited,  which  stand  for  the  current  hard
              limit,  the  current soft limit, and no limit, respectively.  If
              limit is omitted, the current value of the  soft  limit  of  the
              resource  is  printed, unless the -H option is given.  When more
              than one resource is specified, the  limit  name  and  unit  are
              printed before the value.  Other options are interpreted as fol-
              lows:
...
              -n     The maximum number of open file descriptors (most systems
                     do not allow this value to be set)