sys/shell/vfs: make output of vfs df human readable

[benpicco]

Contribution description

Currently vfs df outputs size as filesystem blocks. It is not clear how big a filesystem block is, so the output is hard to interpret.

Instead, output the sizes in Bytes like df -h.

Testing procedure

Run e.g. examples/filesystem:

2022-09-04 12:46:51,962 # > vfs df
2022-09-04 12:46:51,967 # Mountpoint              Total         Used    Available     Capacity
2022-09-04 12:46:51,973 # /sd0                   15223M      129912k    15458440k       0%
2022-09-04 12:46:52,006 # /nvm0                     32M         220k       32548k       0%
2022-09-04 12:46:52,011 # /const                     27           27            0     100%

Issues/PRs references

[maribu]

Looks good to me.

Since you are touching the code anyway: Care to replace "Capacity" in the table header by something more sensible? E.g. when capacity is at 100%, I would assume an empty file storage. I think df is showing Use% there, if I recall correctly

[benpicco]

Looks like this now

2022-09-07 22:09:16,902 # Mountpoint              Total         Used    Available     Use%
2022-09-07 22:09:16,908 # /sd0                15223 MiB   131288 kiB 15457064 kiB       0%
2022-09-07 22:09:16,940 # /nvm0                  32 MiB      220 kiB    32548 kiB       0%
2022-09-07 22:09:16,946 # /const                   27 B         27 B          0 B     100%

[maribu]

Thx :)