Adding custom user options to wordpress

I am trying to add a custom field to the wordpress user profile page. For instance if I wanted to add a field where the user could put in their Linkedin, or Twitter user name, then use that value whenever the user posts a comment, or if the user is an author, to add that value in their posts.

I have a forum (bbpress) integrated so I would also like to use this value to customize the users avatar in the forums.

I am looking at the way Wordpress uses Gravatar. I would like to do something similar. However, I'm not sure where to start. I've written a couple of shortcode plugins in the past, but nothing this complicated.

Any开发者_C百科one have any ideas on where I should begin on this?

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