Linux Command - free

The Linux command free displays the memory usage for the system. It shows how much is free and used. It shows space used by buffers and caches. It also shows swap space usage. All info is parsed out of /proc/meminfo.

It is important to note that much free memory is used for caching and buffering. That memory is still available to be used if needed. If you want to know how much memory is actually available, look at available and not free.

Most common usage, shows usage in human readable format:

free -h

Using -h will display using these units as appropriate:

B	byte
Ki	kibibyte
Mi	mebibyte
Gi	gibibyte
Ti	tebibyte
Pi	pebibyte

Some Options:

-b	bytes
-k	kibibytes
-m	mebibytes
-g	gibibytes
–tebi	tebibytes
–pebi	pebibytes
–kilo	kilobytes
–mega	megabytes
–giga	gigabytes
–tera	terabytes
–peta	petabytes
-h	human readable
-w	wide mode
-c	display count times
-l	low and hi mem stats
-s	continously display every n seconds
–si	power of 1000 units ( kilo, mega, giga )
-t	show total line
-v	show comitted/uncommitted and commit limit

Note:

Power of 1000 - kilo, mega, giga power of 1024 - kibi, mebi, gibi