How to debug url request
$ curl -L -I -v fedex.com
-L makes it follow redirections, otherwise you can only reach the
-I can hide all response body, which is very very verbose.
-v makes the progress talkative, shows details of this request including DNS CA and so on.
or you can:
$ curl -L -s -o /dev/null -v fedex.com
Which send the response body output to the hell.