Returns available disk space
With the various APFS features the value for free disk space returned from
tools such as du or df will not be accurate. This tool uses system
functions to get various measures of available disk space.
The 'Important' value matches the free disk space value shown in Finder.
You can get the details from Apple's documentation:
https://developer.apple.com/documentation/foundation/urlresourcekey/checking_volume_storage_capacity
USAGE: diskspace [--human-readable] [--available] [--important] [--opportunistic] [--total] [<volume-path>]
ARGUMENTS:
<volume-path> path to the volume (default: /)
OPTIONS:
-H, --human-readable Human readable output using unit suffixes
-a, --available Print only the value of the Available Capacity
-i, --important Print only the value of the Important Capacity
-o, --opportunistic Print only the value of the Opportunistic Capacity
-t, --total Print only the value of the Total Capacity
--version Show the version.
-h, --help Show help information.