upsdrvctl would benefit from CLI options to list known devices, and their current health #2567
Description
Note that the related upsdrvsvcctl script (for systemd/SMF unit management) already has such options as:
usage: ./scripts/upsdrvsvcctl/upsdrvsvcctl [OPTIONS] list [<ups>]
list call /usr/local/ups/libexec/nut-driver-enumerator.sh
to list the mapping of service instances to device sections
list <ups> (optionally return the service instance name for one device)
usage: ./scripts/upsdrvsvcctl/upsdrvsvcctl [OPTIONS] show-config [<ups>]
show-config <ups> output config section from ups.conf for device <ups>
show-config ...or all devices if no <ups> argument was passed
which can also be used to probe a device name (is one defined?) without changing the system state.
NOTE: It can be helpful to also add an option (to both) to check if the driver is running, perhaps test that it is alive (e.g. request a data dump via socket protocol, see #1918 #1922 and others).
A loosely related precedent can be seen in scripts/installer/common/ipp-status.