Display the amount of free and used memory in the system.
-b displays memory in number of bytes.
-k displays memory in kilobytes (default).
-m displays memory in megabytes.
-s n repeats the command every n seconds.
-t displays a line containing a summary of the total amounts.
The free command displays information about the physical memory (RAM) and the swap area (on the disk). The output shows the total amount of memory, as well as the amount used and the amount free.