Two simple ways a script can detect if it's online

I didn't want installation of one of TurnKey's components to freeze up too long if it was installed offline so I looked for a nice way to detect that without bringing in additional dependencies.

Two methods stood out...

1. ping Google DNS servers: one second constant delay, regardless if you're online or off:

   # will be true if we're online. Will send 5 packets total.
   is_online() {
       ping -w 1 -i 0.2 8.8.8.8 > /dev/null
   }
   

2. try to resolve a hostname: this will return very quickly if online, 2-3 seconds if we're not, assuming we pass the right args to "host":

   is_online() {
       if 2>&1 host -h | grep -q -- -W; then
               command="host -W 1"
       else
               command="host -s 1"
       fi
   
       $command pool.ntp.org >& /dev/null
   }
   

Since I figured we'd be online more often then not I optimized for that and chose the second method.