[SOLVED] Awk as an ifconfig filter

Awk as an ifconfig filter

I'm new to the whole awk tool, it's seems really complicated to me.

Sample ifconfig output:

enp2s0f1: flags=4099<UP,BROADCAST,MULTICAST>  mtu 1500
        ether xx:xx:xx:xx:xx:xx  txqueuelen 1000  (Ethernet)
        RX packets 0  bytes 0 (0.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 0  bytes 0 (0.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
        inet 127.0.0.1  netmask 255.0.0.0
        inet6 ::1  prefixlen 128  scopeid 0x10<host>
        loop  txqueuelen 1000  (Local Loopback)
        RX packets 338  bytes 27536 (26.8 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 338  bytes 27536 (26.8 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

wlp3s0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet xxx.xxx.xxx.xxx  netmask xxx.xxx.xxx.x  broadcast xxx.xxx.xxx.xxx
        inet6 xxxx::xxxx:xxxx:xxxx:xxxx  prefixlen 64  scopeid 0x20<link>
        ether xx:xx:xx:xx:xx:xx  txqueuelen 1000  (Ethernet)
        RX packets 143296  bytes 172270775 (164.2 MiB)
        RX errors 0  dropped 5  overruns 0  frame 0
        TX packets 32786  bytes 6774762 (6.4 MiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

So far I got a command for ifconfig filter that throws away loopback as well as other unwanted stuff.

ifconfig | awk 'BEGIN{ORS=RS="\n\n"} !/^lo/{print}' | awk '{print $1, $2}' | awk '!/^RX/{print}' | awk '!/^TX/{print}'

And here's an output:

enp2s0f1: flags=4099<UP,BROADCAST,MULTICAST>
ether xx:xx:xx:xx:xx:xx
 
wlp3s0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>
inet xxx.xxx.xxx.xxx
inet6 xxxx::xxxx:xxxx:xxxx:xxxx
ether xx:xx:xx:xx:xx:xx

I researched similar problems, but I want to know how to cut from middle of the line using awk

I already tried a line like: awk '!/flags=/{print}' but it removes whole line that include flags

Desired output:

enp2s0f1:
ether xx:xx:xx:xx:xx:xx

wlp3s0:
inet xxx.xxx.xxx.xxx
ether xx:xx:xx:xx:xx:xx

Solution

You may try this awk:

ifconfig |
awk '
/^[[:alnum:]]+: / { # if we encounter an interface name
   n = $1           # save name in variable n
   p = 1            # set flag p=1
}
# interface does not start with "lo" and protocols are inet or ether
n !~ /^lo/ && /^[[:blank:]]+(inet|ether) / {
   if (p) {         # if flag is set
      print n       # print interface name
      p = 0         # reset flag p=0
   }
   print $1, $2     # print protocol and address
}'