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.   On
              some systems this refers to the limit called
              `address space'.
