Shell Scripting: Proper way to check for internet connectivity?

I found scripts that say they check for internet connectivity. Some check the IP address if the interface is up BUT it does not check for internet connectivity. I found some that uses ping like this: if [ 'ping google.com -c 4 | grep time' != "" ]; then but sometimes this may be unreliable as ping itself may hang for some reason (e.g. waiting for some stuck IO). Any suggestions on the proper/reliable way to check for internet connectivity using scripts? Do I have to use some packages? It needs to be able to check periodically with cron for example, then, do something when the connection goes down like invoke ifup --force [interface]