asn

This is a simple Go program that extracts the subnets associated with a given Autonomous System Number (ASN) from the IP2Location website.

The program takes the ASN as a command-line argument and outputs a list of subnets associated with that ASN.

Installation

To install this program, you must have Go installed on your system. You can install the program using the following command:

go install github.com/melvinsh/asn@latest

This will download the source code, build the program, and install it in your $GOPATH/bin directory. Make sure that $GOPATH/bin is in your $PATH environment variable so that you can run the program from anywhere.

Usage

To run the program and look up the ASN, simply type asn followed by the ASN as the argument. For example, to look up the ASN for 15169 (Google):

The program normalizes the ASN to ensure that it has the correct format, so you can use 15169, AS15169, or as15169 as input.

To print the IP addresses associated with the specified ASN, use the -ips flag. For example:

If the program cannot find the ASN at all, it will output an error message.

If the program cannot find any subnets associated with the specified ASN, it will output nothing.

How it works

The program uses the Go net/http package to make a GET request to the IP2Location website with the specified ASN. It then reads the response and extracts the subnets using regular expressions. Finally, it outputs the subnets to the console.