This teacup subcommand brings your locally-installed packages up to date, including fetching those packages that you don't have. Only fetches packages that can be used with Tcl installations it knows about.
Note that the current teacup has the following options that work with teacup update
DKF: If you cancel the update by pressing Control-C while it is running, you may need to use teacup regenerate to fix things before you can update again.