Introduce ifconfig -a -g groupname

[Rodney W. Grimes]

> On Fri, 2020-05-29 at 19:57 +0700, Eugene Grosbein wrote:
> > Hi!
> > 
> > Currently "ifconfig -a" command that shows status of network
> > interfaces
> > may be combined with flags -d or -u to limit the list to interfaces
> > that are down or up.
> > 
> > The change https://reviews.freebsd.org/D25029 allows it to filter the
> > list
> > by name of interface group with additional flag -g groupname, or -g
> > ^groupname to negate condition
> > (this is different from "ifconfig -g groupname" that shows interface
> > names only
> > and that behaviour is not affected with the change).
> > 
> > I chose caret symbol (^) was choosen to ease both scripted and
> > interactive usage
> > so it does not require extra quotation/escaping, but was told
> > that caret would require escaping in the zsh.
> > 
> > So I ask for suggestions which symbol to choose instead of caret.
> > Benedict Reuschling suggested @ and I'm fine with it
> > if we don't care about Perl code that would require escaping it when
> > running shell code.
> > 
> > For thouse who interested, these are supposed usage examples:
> > 
> > to exclude loopback from the list:
> > 	ifconfig -a -g ^lo
> > to show vlan interfaces only:
> > 	ifconfig -a -g vlan
> > to show tap interfaces that are up:
> > 	ifconfig -aug tap
> > 
> 
> An @ to express negation is insane.  The only characters that have some
> precedent for meaning negation are ~ and !.

And perhaps the original ^, for me anyway.

> Escaping is a fact of life, asking people to remember crazy things like
> @ meaning not is far more onerous than occasionally needing to put
> quotes or escapes on something.

Agree with that fully.

I actually do not like special tokens in arguments to options,
and prefer the suggested use of a different option for exclude,
as in -G vlan to exclude gruop vlan.

I can not think of a command of the top of my head that does
exclusion by special token in option argument and can think
of many with --include --exclude type options.

> -- Ian
-- 
Rod Grimes                                                 rgrimes at freebsd.org