Simple Bash script to collect, deduplicate, and maintain fresh DNS resolvers for recon workflows.

dns-resolvers-fetcher.sh

#!/usr/bin/env bash

# Directory setup (portable & clean)
BASE_DIR="$HOME/.dns-resolvers"
TEMP_DIR="$BASE_DIR/temp"
FINAL_FILE="$BASE_DIR/resolvers.txt"

# Resolver sources
URLS=(
  "https://gist.githubusercontent.com/sirkirby/2e83de47cef930baddedfb12e80a5558/raw/public-dns-resolvers.txt"
  "https://public-dns.info/nameservers.txt"
  "https://public-dns.info/nameservers-all.txt"
  "https://raw.githubusercontent.com/BonJarber/fresh-resolvers/main/resolvers.txt"
  "https://raw.githubusercontent.com/cxosmo/dns-resolvers/main/resolvers.txt"
  "https://raw.githubusercontent.com/kh4sh3i/Fresh-Resolvers/master/resolvers.txt"
  "https://raw.githubusercontent.com/phasip/resolvers/master/resolvers.txt"
  "https://raw.githubusercontent.com/proabiral/Fresh-Resolvers/main/resolvers.txt"
  "https://raw.githubusercontent.com/rix4uni/resolvers/main/resolvers.txt"
  "https://raw.githubusercontent.com/trickest/resolvers/main/resolvers.txt"
  "https://www.cambus.net/files/public-dns-servers.txt"
)

# Create directories
mkdir -p "$TEMP_DIR"

# Cleanup old data
rm -f "$FINAL_FILE"
rm -f "$TEMP_DIR"/* 2>/dev/null

echo "[+] Fetching DNS resolvers from multiple sources..."

# Download resolver lists
i=0
for url in "${URLS[@]}"; do
  ((i++))
  file="$TEMP_DIR/resolver_$i.txt"
  curl -s "$url" -o "$file"
done

echo "[+] Combining & deduplicating resolvers..."

# Merge, filter IPv4 (+ optional port), deduplicate
cat "$TEMP_DIR"/* 2>/dev/null |
  tr -d '\r' |
  grep -E '^[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+(:[0-9]+)?$' |
  sort -u >"$FINAL_FILE"

# Cleanup temp files
rm -rf "$TEMP_DIR"

# Result
if [[ -f "$FINAL_FILE" ]]; then
  COUNT=$(wc -l <"$FINAL_FILE")
  echo "[✓] Resolvers saved to $FINAL_FILE ($COUNT unique)"
else
  echo "[✗] Failed to generate resolver list"
fi

This is a great work, thanks for you effort
but i have notices several source URLs ended in resolvers.txt. The script used basename, which caused downloads to overwrite each other in the temporary directory
here is a slight modification to address this issue

#!/usr/bin/env bash

# Directory setup (portable & clean)
BASE_DIR="$HOME/.dns-resolvers"
TEMP_DIR="$BASE_DIR/temp"
FINAL_FILE="$BASE_DIR/resolvers.txt"

# Resolver sources
URLS=(
  "https://gist.githubusercontent.com/sirkirby/2e83de47cef930baddedfb12e80a5558/raw/public-dns-resolvers.txt"
  "https://public-dns.info/nameservers.txt"
  "https://public-dns.info/nameservers-all.txt"
  "https://raw.githubusercontent.com/BonJarber/fresh-resolvers/main/resolvers.txt"
  "https://raw.githubusercontent.com/cxosmo/dns-resolvers/main/resolvers.txt"
  "https://raw.githubusercontent.com/kh4sh3i/Fresh-Resolvers/master/resolvers.txt"
  "https://raw.githubusercontent.com/phasip/resolvers/master/resolvers.txt"
  "https://raw.githubusercontent.com/proabiral/Fresh-Resolvers/main/resolvers.txt"
  "https://raw.githubusercontent.com/rix4uni/resolvers/main/resolvers.txt"
  "https://raw.githubusercontent.com/trickest/resolvers/main/resolvers.txt"
  "https://www.cambus.net/files/public-dns-servers.txt"
)

# Create directories
mkdir -p "$BASE_DIR"
mkdir -p "$TEMP_DIR"

# Cleanup old data
rm -f "$FINAL_FILE"
rm -f "$TEMP_DIR"/* 2>/dev/null

echo "[+] Fetching DNS resolvers from multiple sources..."

# Download resolver lists
i=0
for url in "${URLS[@]}"; do
  ((i++))
  file="$TEMP_DIR/resolver_$i.txt"
  curl -s "$url" -o "$file"
done

echo "[+] Combining & deduplicating resolvers..."

# Merge, filter IPv4 (+ optional port), deduplicate
cat "$TEMP_DIR"/* 2>/dev/null |
  tr -d '\r' |
  grep -E '^[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+(:[0-9]+)?$' |
  sort -u >"$FINAL_FILE"

# Cleanup temp files
rm -rf "$TEMP_DIR"

# Result
if [[ -f "$FINAL_FILE" ]]; then
  COUNT=$(wc -l <"$FINAL_FILE")
  echo "[✓] Resolvers saved to $FINAL_FILE ($COUNT unique)"
else
  echo "[✗] Failed to generate resolver list"
fi

Great catch! You’re absolutely right about the basename overwrite issue.
Thanks for the clean fix and for adding CR cleanup — really appreciate it 🙌
I’ll update the script with this improvement.