在Linux下怎樣讓top命令啟動之後就按記憶體使用排序（或CPU使用排序）？

NAME
       top - display Linux tasks

SYNOPSIS
       top -hv | -bcHisS -d delay -n iterations -p pid [, pid ...]

       The traditional switches ’-’ and whitespace are optional.

       -b : Batch mode operation
       -c : Command line/Program name toggle
       -d : Delay time interval as:  -d ss.tt (seconds.tenths)
       -h : Help
       -H : Threads toggle
       -i : Idle Processes toggle
       -n : Number of iterations limit as:  -n number
       -u : Monitor by user as:  -u somebody
       -U : Monitor by user as:  -U somebody
       -p : Monitor PIDs as:  -pN1 -pN2 ...  or  -pN1, N2 [,...]
       -s : Secure mode operation
       -S : Cumulative time mode toggle
       -v : Version
       -M : Detect memory units

         W :Write_the_Configuration_File
              This  will save all of your options and toggles plus the current
              display mode and delay  time.   By  issuing  this  command  just
              before  quitting  top, you will be able restart later in exactly
              that same state.

         1 :Toggle_Single/Separate_Cpu_States  --  On/Off
              This command affects how the ’t’ command’s Cpu States portion is
              shown.  Although this toggle  exists  primarily  to  serve  mas-
              sively-parallel SMP machines, it is not restricted to solely SMP
              environments.

       SORTING of task window
         For  compatibility,  this  top  supports  most of the former top sort
         keys.  Since this is primarily a service to former top  users,  these
         commands do not appear on any help screen.
            command   sorted field                  supported
              A         start time (non-display)      No
              M         %MEM                          Yes
              N         PID                           Yes
              P         %CPU                          Yes
              T         TIME+                         Yes