はじめに
コマンドの出力結果を機械的に抽出や加工したい場合、JSONなどの構造化データだと正規表現を書くことをぐっと減らせて便利です。
たまたま ip コマンドは -j または --json というオプションで json 出力できることを知りました。
-p オプションを併用すると、改行付きで表示されて見やすいです。
試した結果をまとめます。
IP アドレスの表示
（一部ダミーの値にしています）
$ ip -j -p addr
[ {
"ifindex": 1,
"ifname": "lo",
"flags": [ "LOOPBACK","UP","LOWER_UP" ],
"mtu": 65536,
"qdisc": "noqueue",
"operstate": "UNKNOWN",
"group": "default",
"txqlen": 1000,
"link_type": "loopback",
"address": "00:00:00:00:00:00",
"broadcast": "00:00:00:00:00:00",
"addr_info": [ {
"family": "inet",
"local": "127.0.0.1",
"prefixlen": 8,
"scope": "host",
"label": "lo",
"valid_life_time": 4294967295,
"preferred_life_time": 4294967295
},{
"family": "inet6",
"local": "::1",
"prefixlen": 128,
"scope": "host",
"valid_life_time": 4294967295,
"preferred_life_time": 4294967295
} ]
},{
"ifindex": 2,
"ifname": "ens192",
"flags": [ "BROADCAST","MULTICAST","UP","LOWER_UP" ],
"mtu": 1500,
"qdisc": "fq_codel",
"operstate": "UP",
"group": "default",
"txqlen": 1000,
"link_type": "ether",
"address": "00:50:56:xx:xx:xx",
"broadcast": "ff:ff:ff:ff:ff:ff",
"addr_info": [ {
"family": "inet",
"local": "192.168.1.100",
"prefixlen": 24,
"broadcast": "192.168.1.255",
"scope": "global",
"dynamic": true,
"noprefixroute": true,
"label": "ens192",
"valid_life_time": 67514,
"preferred_life_time": 67514
},{
"family": "inet6",
"local": "2001:db8::1",
"prefixlen": 64,
"scope": "global",
"dynamic": true,
"noprefixroute": true,
"valid_life_time": 2591817,
"preferred_life_time": 604617
},{
"family": "inet6",
"local": "fe80::5686:4062:1:1",
"prefixlen": 64,
"scope": "link",
"noprefixroute": true,
"valid_life_time": 4294967295,
"preferred_life_time": 4294967295
} ]
},{
"ifindex": 3,
"ifname": "virbr0",
"flags": [ "NO-CARRIER","BROADCAST","MULTICAST","UP" ],
"mtu": 1500,
"qdisc": "noqueue",
"operstate": "DOWN",
"group": "default",
"txqlen": 1000,
"link_type": "ether",
"address": "52:54:00:xx:xx:xx",
"broadcast": "ff:ff:ff:ff:ff:ff",
"addr_info": [ {
"family": "inet",
"local": "192.168.122.1",
"prefixlen": 24,
"broadcast": "192.168.122.255",
"scope": "global",
"label": "virbr0",
"valid_life_time": 4294967295,
"preferred_life_time": 4294967295
} ]
},{
"ifindex": 4,
"ifname": "virbr0-nic",
"flags": [ "BROADCAST","MULTICAST" ],
"mtu": 1500,
"qdisc": "fq_codel",
"master": "virbr0",
"operstate": "DOWN",
"group": "default",
"txqlen": 1000,
"link_type": "ether",
"address": "52:54:00:xx:xx:xx",
"broadcast": "ff:ff:ff:ff:ff:ff",
"addr_info": [ ]
} ]
通常出力（比較用）
$ ip addr
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: ens192: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
link/ether 00:50:56:xx:xx:xx brd ff:ff:ff:ff:ff:ff
inet 192.168.1.100/24 brd 192.168.1.255 scope global dynamic noprefixroute ens192
valid_lft 67528sec preferred_lft 67528sec
inet6 2001:db8::1/64 scope global dynamic noprefixroute
valid_lft 2591832sec preferred_lft 604632sec
inet6 fe80::5686:4062:1:1/64 scope link noprefixroute
valid_lft forever preferred_lft forever
3: virbr0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN group default qlen 1000
link/ether 52:54:00:xx:xx:xx brd ff:ff:ff:ff:ff:ff
inet 192.168.122.1/24 brd 192.168.122.255 scope global virbr0
valid_lft forever preferred_lft forever
4: virbr0-nic: <BROADCAST,MULTICAST> mtu 1500 qdisc fq_codel master virbr0 state DOWN group default qlen 1000
link/ether 52:54:00:xx:xx:xx brd ff:ff:ff:ff:ff:ff
ルーティングテープルの表示
$ ip -j -p route
[ {
"dst": "default",
"gateway": "192.168.1.1",
"dev": "ens192",
"protocol": "dhcp",
"metric": 100,
"flags": [ ]
},{
"dst": "192.168.1.0/24",
"dev": "ens192",
"protocol": "kernel",
"scope": "link",
"prefsrc": "192.168.1.100",
"metric": 100,
"flags": [ ]
},{
"dst": "192.168.122.0/24",
"dev": "virbr0",
"protocol": "kernel",
"scope": "link",
"prefsrc": "192.168.122.1",
"flags": [ "linkdown" ]
} ]
通常出力（比較用）
$ ip route
default via 192.168.1.1 dev ens192 proto dhcp metric 100
192.168.1.0/24 dev ens192 proto kernel scope link src 192.168.1.100 metric 100
192.168.122.0/24 dev virbr0 proto kernel scope link src 192.168.122.1 linkdown
おわりに
他のコマンド、ツールも意外と標準でJSON出力できるということもありそうです。
今一度ヘルプを見るといいかもしれません。
参考
標準機能ではないですが、主要コマンドのパーサーとして jc というものもあります。
github.com
