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.
