Introduce ifconfig -a -g groupname

[Ian Lepore]

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 !.

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.

-- Ian