Golang : Check whether a network interface is up on your machine

Problem:

You have multiple network interfaces on your machine and you need to know the status of a particular network interface is actually up before routing command to it.

Solution:

The code example that follows will use the net package's InterfaceByName() function to probe the interface status for a given interface name. If the given network interface is not available, the program will list out the available network interfaces.

Here you go!

 package main

 import (
 "fmt"
 "net"
 "os"
 "strings"
 )

 func availableInterfaces() {

 interfaces, err := net.Interfaces()

 if err != nil {
 fmt.Print(err)
 os.Exit(0)
 }

 fmt.Println("Available network interfaces on this machine : ")
 for _, i := range interfaces {
 fmt.Printf("Name : %v \n", i.Name)
 }
 }

 func main() {

 if len(os.Args) != 2 {
 fmt.Printf("Usage : %s <interface name>\n", os.Args[0])
 os.Exit(0)
 }

 ifName := os.Args[1]

 byNameInterface, err := net.InterfaceByName(ifName)

 if err != nil {
 fmt.Println(err, "["+ifName+"]")
 fmt.Println("-----------------------------")
 availableInterfaces()
 os.Exit(0)
 }

 if strings.Contains(byNameInterface.Flags.String(), "up") {
 fmt.Println("Status : UP")
 } else {
 fmt.Println("Status : DOWN")
 }

 }

Sample output for my own machine. Your machine will show different results.

$ ./getifacestatus stf0

Status : DOWN

$ ./getifacestatus en3

Status : UP

$ ./getifacestatus eth0

route ip+net: no such network interface [eth0]

-----------------------------

Available network interfaces on this machine :

Name : lo0

Name : gif0

Name : stf0

Name : en3