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🔍 PTRex 🦖 Reverse DNS Lookup Script This Bash script performs reverse DNS (PTR) lookups on a given IP, CIDR range, or a list of IPs from a file. It efficiently resolves hostnames using getent hosts, tracks progress, and runs queries in parallel for speed.

🚀 Features ✅ Accepts a single IP, CIDR range, or file with multiple IPs ✅ Uses getent hosts for reverse DNS (PTR) lookups 🔄 ✅ Parallel execution (up to 50 requests at a time) for faster results ⚡ ✅ Tracks progress dynamically 📊 ✅ Filters and outputs only successful PTR lookups (hostnames only) 🛠

🚀 Installation Ensure you have prips git installed for CIDR expansion:

bash
sudo apt install prips git
git clone https://github.com/povzayd/ptrex.git
cd ptrex && chmod +x *
./ptrex

🚀 Usage Run the script and enter an IP, CIDR range, or a file path when prompted:

bash
./ptrex

🚀 Global Package Making this shell script global will alow you to execute this in any directory For that just move the file ptrex to bin or sbin

bash
mv ptrex /usr/bin
or
mv ptrex /usr/sbin

📌 Example Inputs 1️⃣ Single IP: 8.8.8.8 2️⃣ CIDR Range: 192.168.1.0/24 3️⃣ File with IPs: /path/to/ips.txt

📜 Output Example

[+] Processing IPs from file: ips.txt
[+] Requests made: 12 / 100
[+] Completed!
✅ -> example.com
✅ -> mail.google.com
✅ -> somehost.net

🔎 How It Works 1️⃣ User Input

  • Prompts user to enter an IP, CIDR, or file path
  • Determines input type (single IP, CIDR, or file)

2️⃣ IP Expansion (if CIDR)

  • Uses prips to generate a list of IPs from the CIDR range

3️⃣ Parallel Reverse DNS Lookups

  • Uses getent hosts to fetch PTR records 🕵️
  • Runs up to 50 parallel lookups using xargs -P 50
  • Displays live progress updates

4️⃣ Output Processing

  • Saves only successful hostname lookups 🎯
  • Hides IPs, displaying hostnames only

5️⃣ Cleanup

  • Deletes temporary files after execution 🧹

⚠️ Notes ⚡ Only successful lookups (resolved hostnames) are displayed ⚡ Parallel execution speeds up large queries ⚡ If prips is missing, CIDR expansion will fail

🔮 Future Improvements ✨ Add logging for debugging ✨ Implement timeouts for slow DNS responses ✨ Support custom concurrency levels

This script is great for security assessments, network mapping, and passive reconnaissance when identifying hostnames associated with an IP range. 🌍

*PLEASE NOTE THAT THE SCRIPT GIVES OUTPUT IN THE FORM OF

-> some.pointer.record.abc.com

IF YOU WANT TO REMOVE IT FROM YOUR TXT FILE JUST USE THE COMMAND

sed -i 's/->//g' file.txt

THIS WILL REMOVE -> FROM EACH & EVERY LINE OF YOUR FILE.