free

Display amount of free and used memory in the system. More information: https://manned.org/free.

Display system memory:

free

Display memory in Bytes/KB/MB/GB:

free -{{b|k|m|g}}

Display memory in human-readable units:

free {{[-h|--human]}}

Refresh the output every 2 seconds:

free {{[-s|--seconds]}} {{2}}