dn_expand - Linux

Overview

dn_expand is a utility that transforms a compressed Domain Name (DN) into its expanded form. It reads from standard input or a specified file and prints the expanded representation to standard output. This is useful for converting DNs stored in a compact binary format to a more readable text format.

Syntax

dn_expand [-f] [-r] [-s] [-n sep] [file]

Options/Flags

  • -f: Read a flattened name format (Default).
  • -r: Read a relative name format.
  • -s: Print short names (without the terminating dot).
  • -n sep: Use the specified sep as the separator between label values (Default: space).

Examples

Basic Usage

echo 03www06google03com | dn_expand
www.google.com.

Using Separator

echo 03www06google03com | dn_expand -n :
www:google:com

Read from File

dn_expand -f < input.txt

Common Issues

Incorrect Input Format

Ensure the input is in the correct DN format (flattened or relative). Use -f or -r to specify the format explicitly.

Integration

dn_expand can be integrated with other tools to process DNS data. For example:

dig example.com | grep SOA | awk '{print $4}' | dn_expand -s
ns1.example.com.

Related Commands

  • dig (DNS lookup)
  • nslookup (DNS lookup tool)