ulimit [ -SHacdflmnpstv [ limit ] ... ]
       Set or display resource limits of the shell and the
       processes started by the shell.  The value of limit
       can be a number in the unit specified below or  the
       value  `unlimited'.   By  default, only soft limits
       are manipulated. If the -H flag is given  use  hard
       limits  instead  of soft limits.  If the -S flag is
       given together with the -H flag set both  hard  and
       soft limits.  If no options are used, the file size
       limit (-f) is assumed.  If  limit  is  omitted  the
       current   value  of  the  specified  resources  are
       printed.  When more than one  resource  values  are
       printed  the  limit name and unit is printed before
       each value.

       -a     Lists all of the current resource limits.
       -c     512-byte blocks on the size of core dumps.
       -d     K-bytes on the size of the data segment.
       -f     512-byte blocks on the size of  files  writ-
              ten.
       -l     K-bytes on the size of locked-in memory.
       -m     K-bytes on the size of physical memory.
       -n     open file descriptors.
       -s     K-bytes on the size of the stack.
       -t     CPU seconds to be used.
       -u     processes available to the user.
       -v     K-bytes on the size of virtual memory.
