hi pongpang,
with regards to your question, you should include the full path of your of the database and the text (backup file), the root and the password in order to execute the dumping without errors.
ex.
/usr/local/mysql/bin/mysql -u root -p /usr/local/mysql/var/worldroomevents < /usr/local/mysql/var/worldroomevents.sql
cheers,
jojit