ulimit [ -HSacdfmnt ] [ limit ]
          Set or display a resource limit.  The  value  of  limit
          can  be  a  number  in  the unit specified below or the
          value unlimited.  The H and S flags specify whether the
          hard  limit or the soft limit for the given resource is
          set.
          -a   Lists all of the current resource limits.
          -c   The number of 512-byte blocks on the size of  core
               dumps.
          -d   The number of K-bytes on the size of the data seg-
               ment.
          -f   The number of 512-byte blocks on the size of files
               written.
          -m   The number of K-bytes  on  the  size  of  physical
               memory.
          -n   The number of file descriptors.
          -s   The number of K-bytes on the size of the stack.
          -t   The number of CPU seconds to be used.