ifconfig v2

[David Young <dyoung%pobox.com@localhost>]

I was just reminded what improvements can be made to ifconfig output
when I read this ifconfig output that appeared on current-users today:

wm0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
        capabilities=7ff80<TSO4,IP4CSUM_Rx,IP4CSUM_Tx,TCP4CSUM_Rx>
        capabilities=7ff80<TCP4CSUM_Tx,UDP4CSUM_Rx,UDP4CSUM_Tx,TCP6CSUM_Rx>
        capabilities=7ff80<TCP6CSUM_Tx,UDP6CSUM_Rx,UDP6CSUM_Tx,TSO6>
        enabled=0
        ec_capabilities=7<VLAN_MTU,VLAN_HWTAGGING,JUMBO_MTU>
        ec_enabled=0
        address: 00:26:2d:f3:c8:c7
        media: Ethernet none (none)
        inet 169.254.162.222 netmask 0xffff0000 broadcast 169.254.255.255
        inet6 fe80::226:2dff:fef3:c8c7%wm0 prefixlen 64 scopeid 0x1

The ALL-CAPITALS text is really hard to read.  Let's change that to
lower:

wm0: flags=8843<up,broadcast,running,simplex,multicast> mtu 1500
        capabilities=7ff80<tso4,ip4csum_rx,ip4csum_tx,tcp4csum_rx>
        capabilities=7ff80<tcp4csum_tx,udp4csum_rx,udp4csum_tx,tcp6csum_rx>
        capabilities=7ff80<tcp6csum_tx,udp6csum_rx,udp6csum_tx,tso6>
        enabled=0
        ec_capabilities=7<vlan_mtu,vlan_hwtagging,jumbo_mtu>
        ec_enabled=0
        address: 00:26:2d:f3:c8:c7
        media: Ethernet none (none)
        inet 169.254.162.222 netmask 0xffff0000 broadcast 169.254.255.255
        inet6 fe80::226:2dff:fef3:c8c7%wm0 prefixlen 64 scopeid 0x1

Hmm.  Better, but not by much.

The capability keywords really should be printed in the same form as the
input is typed---i.e., with dashes instead of underscores---and dashes
are easier to type, besides.  So I change the underscores to dashes.  (A
nice property of ifconfig that I miss in other command-line environments
is that a lot of its output is directly reusable in ifconfig command
sentences.)  The hex isn't of much use, so I omit it.  I alphabetize the
capabilities so that if I know which capability I'm looking for, I can
find it without an exhaustive search.  We can afford to use some more
whitespace, and it provides some texture that helps to find and identify
the keywords, so I add some:

wm0: flags < up, broadcast, running, simplex, multicast > mtu 1500
        capabilities:   ip4csum-rx, ip4csum-tx, tcp4csum-rx, tcp4csum-tx,
                        tcp6csum-rx tcp6csum-tx, tso4, tso6,
                        udp4csum-rx, udp4csum-tx, udp6csum-rx, udp6csum-tx
        enabled: <none>
        ether capabilities: vlan-mtu, vlan-hwtagging, jumbo-mtu
        ether enabled: <none>
        address: 00:26:2d:f3:c8:c7
        media: Ethernet none (none)
        inet 169.254.162.222 netmask 0xffff0000 broadcast 169.254.255.255
        inet6 fe80::226:2dff:fef3:c8c7%wm0 prefixlen 64 scopeid 0x1

Most of the time, that is much more information than I need, so I'm
going to delete the capabilities and many of the flags from the default
display.  I also delete the mtu, which isn't important to me unless it's
different from the default:

wm0: flags < up, running >
        address: 00:26:2d:f3:c8:c7
        media: Ethernet none (none)
        inet 169.254.162.222 netmask 0xffff0000 broadcast 169.254.255.255
        inet6 fe80::226:2dff:fef3:c8c7%wm0 prefixlen 64 scopeid 0x1

Finally, I get more use out of mask lengths than netmasks, and rarely is
the broadcast address useful to me:

wm0: flags < up, running >
        address: 00:26:2d:f3:c8:c7
        media: Ethernet none (none)
        inet 169.254.162.222 prefixlen 16
        inet6 fe80::226:2dff:fef3:c8c7%wm0 prefixlen 64 scopeid 0x1

Finally, for the sake of consistency, let's put all of the addresses,
even the link-layer address, into <family> <address> form:

wm0: flags < up, running >
        media: Ethernet none (none)
        link 00:26:2d:f3:c8:c7
        inet 169.254.162.222 prefixlen 16
        inet6 fe80::226:2dff:fef3:c8c7%wm0 prefixlen 64 scopeid 0x1

That is an efficient and consistent display.  I estimate that it will
meet my information needs more than 95% of the time when I run 'ifconfig
wm0', and it will meet my needs more quickly than the status quo because
it is less cluttered and more compact.

If I need more information, I will ask for it with ifconfig -v wm0:

wm0: flags < up, broadcast, running, simplex, multicast > mtu 1500
        capabilities:   ip4csum-rx, ip4csum-tx, tcp4csum-rx, tcp4csum-tx,
                        tcp6csum-rx tcp6csum-tx, tso4, tso6,
                        udp4csum-rx, udp4csum-tx, udp6csum-rx, udp6csum-tx
        enabled: <none>
        ether capabilities: vlan-mtu, vlan-hwtagging, jumbo-mtu
        ether enabled: <none>
        media: Ethernet none (none)
        link 00:26:2d:f3:c8:c7
        inet 169.254.162.222 prefixlen 16 broadcast 169.254.255.255
        inet6 fe80::226:2dff:fef3:c8c7%wm0 prefixlen 64 scopeid 0x1

Dave

-- 
David Young
dyoung%pobox.com@localhost    Urbana, IL    (217) 721-9981