What is the difference between ping -w and ping -W?

From man ping:

   -w deadline
          Specify a timeout, in seconds, before ping exits regardless of how many packets have been sent or received. In this case ping does not stop after count packet are sent, it waits either for deadline expire or until count probes are answered or for some error
          notification from network.

   -W timeout
          Time to wait for a response, in seconds. The option affects only timeout in absense of any responses, otherwise ping waits for two RTTs.

That is, -w sets the timeout for the entire program session. If you set -w 30, ping (the program) will exit after 30 seconds.

-W on the other hand sets the timeout for a single ping. If you set -W 1, that particular ping attempt will time out.

As for how to set an individual ping timeout of 200ms, I don't believe this can be done with iputils' version of ping. You might want to try directly programming with an ICMP library.

All good answers, but watch out for this quirk if (like me) you're porting code between platforms. The text below is from the respective 'man ping' documentation.

On Mac OS X:

-W waittime

Time in milliseconds to wait for a reply for each packet sent.

On Raspberry Pi:

-W timeout

Time to wait for a response, in seconds.

I coded on the Mac to wait 1 second (1,000 ms) as -W 1000, but when this code moved to the Pi, it waited for up to 1,000 secs!