Imagine you want to test a web service/site secured by SSL and a password. Here is how to do that from the commandline:
In this example these values are used:
Generate the base64 encoded username and password combination:
echo -n "username:password" | openssl base64 -base64
The output will be something like dXNlcm5hbWU6cGFzc3dvcmQ=. Paste that string into a file called "input.txt".
GET /some/directory/some-file.html HTTP/1.1
Authentication: basic dXNlcm5hbWU6cGFzc3dvcmQ=
N.B. The two empty lines are required.
Next, throw that file into openssl:
(cat input.txt ; sleep 3) | openssl s_client -connect example.com:443
The output will show all headers and HTML content so you can grep all you want.