How to test an Internet connection with bash?

Question

How can an internet connection be tested without pinging some website? I mean, what if there is a connection but the site is down? Is there a check for a connection with the

Answer 1

Ping was designed to do exactly what you're looking to do. However, if the site blocks ICMP echo, then you can always do the telnet to port 80 of some site, wget, or curl.

Answer 2

shortest way: fping 4.2.2.1 => "4.2.2.1 is alive"

i prefer this as it's faster and less verbose output than ping, downside is you will have to install it.

you can use any public dns rather than a specific website.

fping -q google.com && echo "do something because you're connected!"

-q returns an exit code, so i'm just showing an example of running something you're online.

to install on mac: brew install fping; on ubuntu: sudo apt-get install fping

Answer 3

The top answer misses the fact that you can have a perfectly stable connection to your default gateway but that does not automatically mean you can actually reach something on the internet. The OP asks how he/she can test a connection with the world. So I suggest to alter the top answer by changing the gateway IP to a known IP (x.y.z.w) that is outside your LAN.

So the answer would become:

ping -q -w 1 -c 1 x.y.z.w > /dev/null && echo ok || echo error

Also removing the unfavored backticks for command substitution^[1].

If you just want to make sure you are connected to the world before executing some code you can also use:

if ping -q -w 1 -c 1 x.y.z.w > /dev/null; then
    # more code
fi

Answer 4

Without ping

#!/bin/bash

wget -q --spider http://google.com

if [ $? -eq 0 ]; then
    echo "Online"
else
    echo "Offline"
fi

-q : Silence mode

--spider : don't get, just check page availability

$? : shell return code

0 : shell "All OK" code

Without wget

#!/bin/bash

echo -e "GET http://google.com HTTP/1.0\n\n" | nc google.com 80 > /dev/null 2>&1

if [ $? -eq 0 ]; then
    echo "Online"
else
    echo "Offline"
fi

Answer 5

make sure your network allow TCP traffic in and out, then you could get back your public facing IP with the following command

curl ifconfig.co

Answer 6

Pong doesn't mean web service on the server is running; it merely means that server is replying to ICMP echo. I would recommend using curl and check its return value.