Whoami in SharePoint

One of the nicest things in SharePoint is that you can access it not only through the web interface, but through its web services as well. Combining this with AJAX, you can build pretty good user interfaces with a SharePoint backend.
When doing this you’ll definitely be interested in knowing who is currently logged in.
So if you are modifying a SharePoint generated page (like NewForm.aspx, EditForm.aspx or a page associated with a view) and add (D)HTML code to it, you can easily access the _spUserId variable which holds the current logged in user ID in SharePoint.
From this point on if you’re interested in more details you just simply run a query against the user list using SharePoint web services.
If you want to have these information in a page of your own, you can simply run that query using the CAML tag UserID.

<Query>
  <Where>
    <Eq>
      <FieldRef Name="ID"/>
      <Value Type="Integer"><UserID Type="Integer"/></Value>
    </Eq>
  </Where>
</Query<

Just as a note, don’t forget to put Type="Integer" in there.

If you wonder how I got over this, you should read my other article.