Doesn't work with busybox

[Nathaniel Hill]

Just for the record, this doesn't seem to work with the output from busybox's ping, which is quite common in Docker setups these days with so many alpine images.

For anyone coming across this trying to get this working on your alpine Docker image, try:

RUN apk add iputils

[Mond WAN]

Update the README to include your solution. THanks

[Weihong Guan]

It is interesting though. ping command is workable in alpine shell.