In my bash scripts I have been using something like:

until fping -u google.com; do echo "$0[$$] Network/DNS down?? $(date)" 1>&2 && sleep $(($RANDOM%(1 + ++trynum * 1) +1)).222; done

to test for online connectivity.

It halts in place, sleeping growing random intervals, until it can ping google.com again.

Problem: At some sites ICMP pings are blocked altogether, and web pages are still reachable. What's a short way to test for this general case?

Based on that test I will switch over to an http-based test like the exit status of

curl -s google.com >/dev/null

if that is a good one.