Awk as an ifconfig filter

Question

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

Answer 1

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
}'

Answer 2

$ cat tst.awk
/^[[:alnum:]]/ {
    f = ($1 == "lo:" ? 0 : 1)
    if (f) {
        print sep $1
        sep = ORS
    }
}
f && ($1 ~ /^(ether|inet)$/) {
    print $1, $2
}

$ awk -f tst.awk file
enp2s0f1:
ether xx:xx:xx:xx:xx:xx

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

Answer 3

ifconfig | awk '/^lo/,/\n\n/{ e=1 }!e && $1!~/^(RX|TX)$/{ print $1,$1~/:/?"":$2}'

• The /^lo/,/\n\n/ will set e to 1 for the loopback part.

• We only print something if e equals 0 and

  if the first element does not start with an R or T.

• Finally, only print $2 is $1 does not contain a :

Answer 4

I found this command to be more helpful to filter unwanted stuff from the ifconfig command:

/sbin/ifconfig/ eth0 | grep 'inet' | cut -d: -f2 |awk '{print $2}'

eth0 - to get eth0 ip details inet - shows only strings containing inet cut -d: this will convert all inet containing string into a list -f2 to access 2nd string/line awk '{print $2}' to get the desire output where $2- for string index at 2nd position