domains2ips

This script resolves a list of domains and generates two files, one with the resolved IPv4 addresses and the other with the resolved IPv6 addresses.

Usage

Usage: ./domains2ips.sh
-i, --input <file>  Read file with domains, separated by newline
-h, --help          Print usage

Input

This script expects a file with domains, separated by newline.

security.ubuntu.com
de.archive.ubuntu.com

Output

This script generates three files:

ipv4.out

91.189.91.81
91.189.91.82
91.189.91.83
185.125.190.81
185.125.190.82
185.125.190.83

ipv6.out

2620:2d:4000:1::101
2620:2d:4000:1::102
2620:2d:4000:1::103
2620:2d:4002:1::101
2620:2d:4002:1::102
2620:2d:4002:1::103

logfile

2025-05-02 18:14:29 [DEBUG] security.ubuntu.com: 185.125.190.81
2025-05-02 18:14:29 [DEBUG] security.ubuntu.com: 185.125.190.83
2025-05-02 18:14:29 [DEBUG] security.ubuntu.com: 91.189.91.81
2025-05-02 18:14:29 [DEBUG] security.ubuntu.com: 91.189.91.83
2025-05-02 18:14:29 [DEBUG] security.ubuntu.com: 91.189.91.82
2025-05-02 18:14:29 [DEBUG] security.ubuntu.com: 185.125.190.82
2025-05-02 18:14:30 [DEBUG] security.ubuntu.com: 2620:2d:4000:1::101
2025-05-02 18:14:30 [DEBUG] security.ubuntu.com: 2620:2d:4000:1::102
2025-05-02 18:14:30 [DEBUG] security.ubuntu.com: 2620:2d:4002:1::103
2025-05-02 18:14:30 [DEBUG] security.ubuntu.com: 2620:2d:4002:1::102
2025-05-02 18:14:30 [DEBUG] security.ubuntu.com: 2620:2d:4002:1::101
2025-05-02 18:14:30 [DEBUG] security.ubuntu.com: 2620:2d:4000:1::103

Further Details

If domain can be resolved respectively if ipv4s / ipv6s is not empty, then write each IP address into the output file and set the resolved flag.

if [ -n "$ipv4s" ]; then
    while IFS= read -r ip; do
      log "DEBUG" "$domain: $ip"
      echo "$ip" >> $OUT_FILE_IPV6
    done <<< "$ipv4s"
    resolved=true
fi

If a domain cannot be resolved, then write a log entry.

if [ "$resolved" = false ]; then
  log "DEBUG" "$domain: resolution failed"
fi

Because the IP addresses were appended to the output file, e. g. echo "$ip" >> $OUT_FILE_IPV6, the first line is always empty. Therefore, these lines will be removed.

sed -i '/^$/d' "$OUT_FILE_IPV4"
sed -i '/^$/d' "$OUT_FILE_IPV6"

sort -t . -k1,1n -k2,2n -k3,3n -k4,4n -o "$OUT_FILE_IPV4" "$OUT_FILE_IPV4" sorts the IPv4 addresses in a ascending order and replaces the content of the output file with the sorted list.

In case of some domains, the output without grep includes a domain, too.

feeds.transistor.fm.cdn.cloudflare.net.
104.22.52.147
172.67.13.71
104.22.53.147

Therefore, the output of dig will be filtered to get only the addresses.

ipv4s=$(dig +short A feeds.transistor.fm | grep -Eo '^[0-9.]+$')