When the mysql command line client errors out during an import, the import stops. So I would first recommend running any imports you do in a screen session, which will help prevent the import form being killed due to inactivity or your session being terminated.
As for how to tell when the import is complete, your command will finish, and you will see your command prompt again with no error messages. To verify that the import is still running, connect to MySQL in another session and run “show processlist;” a few times to see the inserts from your import. To see how far along the import is, you could do a COUNT of the rows in a table being imported (with the understanding that anything you do may slow down the import further).