Bash script to (more or less) reliably check if the Internet is up

Question

I need a Bash (or a plain shell) script to put in a cronjob that every minute checks if the Internet is up.

This is how I did it:

#! /bin/sh

host1=google.com
host2=wikipedia.org
curr_date=`date +"%Y%m%d%H%M"`

echo -n "${curr_date};"
((ping -w5 -c3 $host1 || ping -w5 -c3 $host2) > /dev/null 2>&1) && 
echo "up" || (echo "down" && exit 1)

How would you do it? Which hosts would you ping?

Clarifications:

• By "internet is up", I mean my internet connection.

• By "up", I mean to have usable connection (doesn't really matter if we are talking about the DNS being down or the connection is really really slow [mind the -w for timeout]). That is also why I didn't include any IP but only hosts.

Should I also ping Stack Overflow? I mean, if I can't access Google, Wikipedia or Stack Overflow, I don't want Internet :p

Answer 1

That one seems like a good solution. Just add a few more hosts, and maybe some pure IP hosts so you don't rely on DNS functioning (which in itself depends on your definition of "up").

Answer 2

Thanks for your code, it works great, I've left only one line actually:

((ping -w5 -c3 8.8.8.8 || ping -w5 -c3 4.2.2.1) > /dev/null 2>&1) && echo "up" || (echo "down" && exit 1)