The "mysql" command and the "mysqladmin" command could both be used to produce this output with a one-liner, but in both cases they're going to prompt you for login credentials, which is I assume what's biting you. The thing to do in this case is to make use of the ~/.my.cnf file containing the appropriate information to automatically log you in -- both mysql and mysqladmin will utilize the credentials found in ~/.my.cnf if it exists.
As the user you want to run the "watch" command with, type "vim ~/.my.cnf" or "nano ~/.my.cnf", whichever editor you prefer, and if it doesn't exist or if it does exist, make it look like this:
user = USERNAME
password = PASSWORD
host = HOSTNAME
USERNAME is the MySQL user you want (could be root if that's what you want), PASSWORD is that user's password, and HOSTNAME is the hostname (if you're on the MySQL box, this is "localhost" w/o the quotes).
If you set up ~/my.cnf properly, it will be noticed by 'mysql' and 'mysqladmin' binaries and used to login if you don't specify a different user or password request with '-u' and '-p' options.