This is generally useful, but in some cases particularly: when
implementing enumeration calls that use the "more" flag to return
multiple replies then for the first reply we need to return an error in
case the list of objects to enumerate is empty, usually so form of
"NoSuchXYZ" error. In many cases this shouldn't really be treated as
error, as an empty list probably more than not is as valid as a list
with one, two or more entries.
For putting together "varlinkctl call" command lines it's useful to
quickly enumerate all methods implemented by a service. Hence, let's add
a new "list-methods" which uses the introspection data of a service to
quickly list methods.
This is implemented as a special flavour of the "introspect" logic,
and just suppresses all output except for the method names.
let's make it easier to use the introspection functionality of
"varlinkctl": if no interface name is shown, display the introspection
data of all available interfaces. Moreover, allow that multiple
interfaces can be listed, in which case we enumerate them all.
This relieves the user from having to list interfaces first in order to
find the ones which to introspect.
It exposes the varlink_collect() call we internally provide: it collects
all responses of a method call that is issued with the "more" method
call flag. It then returns the result as a single JSON array.
This uses openssh 9.4's -W support for AF_UNIX. Unfortunately older versions
don't work with this, and I couldn#t figure a way that would work for
older versions too, would not be racy and where we'd still could keep
track of the forked off ssh process.
Unfortunately, on older versions -W will just hang (because it tries to
resolve the AF_UNIX path as regular host name), which sucks, but hopefully this
issue will go away sooner or later on its own, as distributions update.
Fedora is still stuck at 9.3 at the time of posting this (even on
Fedora), even though 9.4, 9.5, 9.6 have all already been released by
now.
Example:
varlinkctl call -j ssh:root@somehost:/run/systemd/io.systemd.Credentials io.systemd.Credentials.Encrypt '{"text":"foobar"}'
