hostsfile

README

Hostsfile

The /etc/hosts parsing and resolver library for golang

Hostsfile is a go (golang) package for parsing hosts files and performing reverse IP -> hostname lookups which are file-based (e.g. via /etc/hosts).

This can be helpful to determine if there is a prettier (or known) hostname available for an IP address.

These lookups are "extremely inexpensive" compared to normal IP reverse DNS lookups because no network communication is required, as these lookups are all file-based! Naturally, the (obvious) tradeoff/downside is that this only works in cases where the IP mapping exists in the hostsfile.

Get it

go get -u github.com/jaytaylor/go-hostsfile

Usage

package main

import (
    "fmt"

    "github.com/jaytaylor/go-hostsfile"
)

func main() {
    res, err := hostsfile.ReverseLookup("127.0.0.1")
    if err != nil {
        panic(err)
    }
    fmt.Printf("%v maps 127.0.0.1 to the following names: %v", hostsfile.HostsPath, res)
}

Output:

/etc/hosts maps 127.0.0.1 to the following names: [localhost]

Supported Operating Systems

Tested and verified working on:

• Linux
• Mac OS X
• Windows

It should also support Plan9, though admittedly I don't have a plan9 installation available to verify that one ;)

Unit-tests

Running the unit-tests is straightforward and standard:

go test

License

Permissive MIT license.

Contact

You are more than welcome to open issues and send pull requests if you find a bug or want a new feature.

If you appreciate this library please feel free to drop me a line and tell me! It's always nice to hear from people who have benefitted from my work.

Email: jay at (my github username).com

Twitter: @jtaylor

Documentation

Index

• Variables
• func ParseHosts(hostsFileContent []byte, err error) (map[string][]string, error)
• func ReadHostsFile() ([]byte, error)
• func ReverseLookup(ip string) ([]string, error)

Variables

var HostsPath = `/etc/hosts`

Functions

func ParseHosts

func ParseHosts(hostsFileContent []byte, err error) (map[string][]string, error)

ParseHosts takes in hosts file content and returns a map of parsed results.

func ReadHostsFile

func ReadHostsFile() ([]byte, error)

ReadHostsFile reads the hosts file.

func ReverseLookup

func ReverseLookup(ip string) ([]string, error)

ReverseLookup takes an IP address and returns a slice of matching hosts file entries.