nslookup-bulk.sh

#!/usr/bin/env bash
set -euo pipefail

if [[ $# -lt 1 ]]; then
    echo "Usage: $0 <file>"
    exit 1
fi

FILE="$1"

if [[ ! -f "$FILE" ]]; then
    echo "File not found: $FILE"
    exit 1
fi

# prefer 'dig' if available, otherwise fall back to 'host'
if command -v dig &>/dev/null; then
    while IFS= read -r line; do
        name="${line#"${line%%[![:space:]]*}"}"  # trim leading whitespace
        name="${name%"${name##*[![:space:]]}"}"  # trim trailing whitespace
        [[ -z "$name" || "$name" == \#* ]] && continue

        ips=$(dig +short A "$name" 2>/dev/null)
        if [[ -n "$ips" ]]; then
            printf "%s -> %s\n" "$name" "$(echo "$ips" | paste -sd ', ')"

        else
            printf "%s -> [no record]\n" "$name"
        fi
    done < "$FILE"
elif command -v host &>/dev/null; then
    while IFS= read -r line; do
        name="${line#"${line%%[![:space:]]*}"}"
        name="${name%"${name##*[![:space:]]}"}"
        [[ -z "$name" || "$name" == \#* ]] && continue

        out=$(host "$name" 2>/dev/null) || true
        if echo "$out" | grep -q "has address"; then
            ips=$(echo "$out" | grep "has address" | awk '{print $NF}' | paste -sd ', ')
            printf "%s -> %s\n" "$name" "$ips"
        else
            printf "%s -> [no record]\n" "$name"
        fi
    done < "$FILE"
else
    echo "Neither 'dig' nor 'host' found — install bind-tools or dnsutils"
    exit 1
fi