Display statistics about memory usage: total free, used, physical, swap, shared, and buffers used by the kernel.
Calculate memory in bytes.
Default. Calculate memory in kilobytes.
Calculate memory in megabytes.
Do not display “buffer adjusted” line. The -o switch disables the display “-/+ buffers” line that shows buffer memory subtracted from the amount of memory used and added to the amount of free memory.
Check memory usage every time seconds.
Display all totals on one line at the bottom of output.
Display version information.