Let's say you have a string that contains forward slash, like this.

http://www.example.com/foo/bar

I find awk to be the easiest tool to cut this string apart. $1 will print the protocol (http in this example).

~]# echo "http://www.example.com/foo/bar" | awk -F'/' '{print $1}'
http

$3 will print the hostname (www.example.com).

~]# echo "http://www.example.com/foo/bar" | awk -F'/' '{print $3}'
www.example.com

$4 will print the first part of the context root (foo in this example).

~]# echo "http://www.example.com/foo/bar" | awk -F'/' '{print $4}'
foo