Calculate the compression ratio of a set of files on a btrfs filesystem. See also
btrfs filesystem
for recompressing a file by defragmenting it. More information: https://github.com/kilobyte/compsize.
sudo compsize path/to/file_or_directory
sudo compsize --one-file-system path/to/file_or_directory
sudo compsize --bytes path/to/file_or_directory