Question

Why can I write the command

ping www.google.com

but not

ping www.google.com/

or

ping http://www.google.com

The latter two yield an “unknown host” error.

Answer 1

Ping is used to tell if a host (hostname or IP address) is alive. It uses the ICMP protocol to do so. It does not know anything about URLs or web servers.

What you probably want is a http ping utility, like http-ping. Or you can use tools like curl, or wget to retrieve website index pages and measure the latency that way.

Example with curl (this does a HEAD request):

$ time curl -I http://www.cnn.com >/dev/null

real    0m0.242s    <== 242 milliseconds
user    0m0.015s
sys     0m0.016s

Example with curl for GET request:

$ time curl http://www.cnn.com >/dev/null

real    0m0.783s    <== 783 milliseconds
user    0m0.031s
sys     0m0.030s

This will give you a crude idea of how responsive the web server is from your host.