Search notes:

Shell command: free

free reports the amount of free and used physical memory and swap space.

free: grep /proc/meminfo 'MemFree\|SwapFree' (Sometimes slightly different. Because of delay between executing commands?)

shared: used by tmpfs

grep Shmem /proc/meminfo

cache: page cache and slabs.

grep '^Cached:\|Slab /proc/meminfo

buffers: used for kernel buffers

grep Buffers /proc/meminfo

available: An estimation on how much memory a new process might allocate.

grep MemAvailable /proc/meminfo

total: cat /proc/meminfo | grep MemInfo

total = used + free + buffers + cache

Actual free memory

Since cache (and also buffers?) are used to speed up hard disk access, the actual free memory calculates as

free + cache + buffers

-m: megabytes

free -m

-w is the wide option: the buff/cache column is shown separately as buffers and cache.

free -w