Logging into an application using shell?

I'm working on a small side project for myself. One of the features of it is being able to login into battle.net using shell.

I know how to run the application using shell, but I'm not sure how input info into specific fields. I.e. the login and password.

How can I do this?

You can write it in pure shell commands, I'm hoping to translate this into a script which will log you into a specific account.