* `-h`/`-H`, `--help`:
display help/long help and exit
* `-V`, `--version`:
- display version number and exit.
+ display version number and immediately exit.
+ note that, since it exits, flags specified after `-V` are effectively ignored.
Advanced: `-vV` also displays supported formats.
`-vvV` also displays POSIX support.
- `-q` will only display the version number, suitable for machine reading.
+ `-qV` will only display the version number, suitable for machine reading.
* `-v`, `--verbose`:
verbose mode, display more information
* `-q`, `--quiet`: