IfInfo

To create a program in Go that lists all available network interfaces and their IP addresses, you need to create a few files: main.go for the main logic, and optionally, a interfaces.go file for the interface-handling functionality. Here is a step-by-step guide:

Step 1: Initialize the Go Module

First, create a new directory for your project and initialize the Go module.

mkdir ifinfo
cd ifinfo
mkdir lib
go mod init github.com/username/ifinfo

Step 2: Create the `interfaces.go` File

Create a lib/interfaces.go file in to handle the functionality of listing network interfaces.

package lib

import (
	"fmt"
	"net"
)

// ListInterfaces retrieves all network interfaces and their IP addresses.
func ListInterfaces() {
	interfaces, err := net.Interfaces()
	if err != nil {
		fmt.Printf("Error retrieving interfaces: %v\n", err)
		return
	}

	fmt.Println("Available Network Interfaces:")
	for _, iface := range interfaces {
		fmt.Printf("Name: %s, MTU: %d, HardwareAddr: %s, Flags: %s\n", iface.Name, iface.MTU, iface.HardwareAddr, iface.Flags)

		addrs, err := iface.Addrs()
		if err != nil {
			fmt.Printf("  Error retrieving addresses: %v\n", err)
			continue
		}

		for _, addr := range addrs {
			fmt.Printf("  Address: %s\n", addr.String())
		}
		fmt.Println()
	}
}

Step 3: Create the `main.go` File

Create a main.go file to use the network interface listing functionality.

package main

import (
	"github.com/username/ifinfo/lib"
)

func main() {
	lib.ListInterfaces()
}

Step 4: Run the Program

Run the program using the go run command.

go run main.go

The program will retrieve and display:

All available network interfaces on the system.
The associated IP addresses for each interface.

Example Output

For a machine with several interfaces:

Available Network Interfaces:
Name: lo
  Address: 127.0.0.1/8
  Address: ::1/128

Name: eth0
  Address: 192.168.1.100/24
  Address: fe80::1a2b:3c4d:5e6f:7g8h/64

Name: wlan0
  Address: 10.0.0.100/24
  Address: fe80::1234:5678:abcd:ef12/64

Notes

The program uses the net package, which provides tools to list interfaces and their details.
IP addresses include both IPv4 and IPv6, displayed with their subnet masks.
If an interface has no assigned IP address, it will still be listed, but without any associated address output.

Extensions

You can modify the program to filter interfaces (e.g., only show interfaces with an active connection or only display IPv4 addresses).
Add error handling to improve robustness in environments with unusual network configurations.

Last modified: 08 January 2025