Truncate email address in username field?

[Ken Statham]

Hi,

I imported a bunch of users using their email address as the username. I need to update every user who has an email address in the username field, to convert the username to just what is before the @ symbol.

Example:

[e-mail] becomes user

and

[e-mail] becomes user.name

Can anybody help with this?

Thanks in advance!
Ken