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 written.
       -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'.
