One output or every output

set with no --output replaces every choice, per-output ones included; with --output NAME it sets that output only.

One output or every output

set with no --output replaces every choice, per-output ones included; with --output NAME it sets that output only, and the choice is kept by name, so the monitor shows it again when it is unplugged and plugged back in. A name no output has right now is an error (exit 1) and changes nothing. clear does the same with nothing to show.