awk — IPv6

Extract IPv6 addresses from ip -6 addr show

ip -6 addr show | awk '/inet6/{split($2,a,"/"); print $NF, a[1], "/"a[2]}'

Extract only global-scope IPv6 addresses — skip link-local

ip -6 addr show scope global | awk '/inet6/{split($2,a,"/"); print a[1]}'

Parse ip -6 route — destination, via, device

ip -6 route | awk '{
    dst=$1; dev=""; via=""
    for(i=2;i<=NF;i++){
        if($i=="dev") dev=$(i+1)
        if($i=="via") via=$(i+1)
    }
    printf "%-40s via %-30s dev %s\n", dst, (via?via:"-"), dev
}'

Extract remote IPv6 and port from ss -6 -tn

ss -6 -tn | awk 'NR>1 {
    peer=$5
    n=split(peer,a,":")
    port=a[n]
    addr=substr(peer,1,length(peer)-length(port)-1)
    gsub(/^\[|\]$/,"",addr)
    printf "%-40s port %s\n", addr, port
}'

Count IPv6 connections per remote address

ss -6 -tn | awk 'NR>1 {
    peer=$5
    n=split(peer,a,":")
    port=a[n]
    addr=substr(peer,1,length(peer)-length(port)-1)
    gsub(/^\[|\]$/,"",addr)
    count[addr]++
} END{for(a in count) printf "%-40s %d\n", a, count[a]}' | sort -k2 -rn

Classify IPv6 — link-local vs global vs ULA vs loopback

ip -6 addr show | awk '/inet6/{
    split($2,a,"/"); addr=a[1]
    if(addr ~ /^fe80/)       type="link-local"
    else if(addr ~ /^fd/)    type="ULA"
    else if(addr ~ /^fc/)    type="ULA"
    else if(addr == "::1")   type="loopback"
    else                     type="global"
    printf "%-8s %s\n", type, addr
}'

Classify arbitrary IPv6 list from heredoc

awk '{
    addr=$1
    if(addr ~ /^fe80/)       type="link-local"
    else if(addr ~ /^f[cd]/) type="ULA"
    else if(addr == "::1")   type="loopback"
    else if(addr ~ /^ff/)    type="multicast"
    else                     type="global"
    printf "%-10s %s\n", type, addr
}' <<'EOF'
fe80::1a2b:3c4d:5e6f:7890
2607:f8b0:4004:800::200e
fd12:3456:789a::1
::1
ff02::1
2001:db8::42
EOF

Parse IPv6 neighbor table — address, device, state

ip -6 neigh | awk '{
    addr=$1; dev=""; lladdr=""; state=$NF
    for(i=2;i<=NF;i++){
        if($i=="dev") dev=$(i+1)
        if($i=="lladdr") lladdr=$(i+1)
    }
    printf "%-40s dev %-8s mac %-18s %s\n", addr, dev, (lladdr?lladdr:"-"), state
}'

Extract AAAA records from dig output

dig AAAA google.com +short | awk '/^[0-9a-f:]+$/{print}'

Extract AAAA from dig full output — answer section only

dig AAAA google.com | awk '/^;; ANSWER SECTION:/{p=1; next} /^;;/{p=0} p && /AAAA/{print $1, $5}'

Expand compressed IPv6 to full 8-group notation

echo "2001:db8::42" | awk -F: '{
    # Count existing groups and find :: position
    n=NF; expand=0
    for(i=1;i<=n;i++) if($i=="") expand=i
    # Build full 8 groups
    g=0
    for(i=1;i<=n;i++){
        if($i=="" && !done){
            need=9-n  # groups to insert (9 because :: splits into 2 empty fields)
            for(j=1;j<=need;j++) group[++g]="0000"
            done=1
        } else if($i!=""){
            group[++g]=sprintf("%04s",$i)
            gsub(/ /,"0",group[g])
        }
    }
    for(i=1;i<=8;i++) printf "%s%s", group[i], (i<8?":":"\n")
}'

Compress full IPv6 — strip leading zeros (partial compression)

echo "2001:0db8:0000:0000:0000:0000:0000:0042" | awk -F: '{
    for(i=1;i<=NF;i++){
        v=$i+0  # force numeric to strip leading zeros
        printf "%x%s", v, (i<NF?":":"\n")
    }
}'