MySQL Sandboxで./use_allをrootでやりたい

$ ./use_all "select current_user"
# server: 1:
current_user
msandbox@localhost
# server: 2:
current_user
msandbox@localhost
# server: 3:
current_user
msandbox@localhost
# server: 4:
current_user
msandbox@localhost

$ export MYCLIENT_OPTIONS="-uroot"

$ ./use_all "select current_user"
# server: 1:
current_user
root@localhost
# server: 2:
current_user
root@localhost
# server: 3:
current_user
root@localhost
# server: 4:
current_user
root@localhost