mysql启动的时参数文件中的[mysql]下的参数没有生效

my.cnf下的参数如下
[mysqld]
此处省略.....

[mysql]
#no-auto-rehash
prompt='\u@\h:\p\d mysql>'
#max_allowed_packet = 1024M ##影响mysql导人的速度
#default_character_set = gbk

启动方式
mysqld --defaults-file=/etc/my.cnf &

启动后prompt没有生效
[root@mysqldb15 ~]# mysql -uroot -p -S /tmp/mysql3306.sock
Enter password:
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 1
Server version: 5.6.29-log MySQL Community Server (GPL)

Copyright (c) 2000, 2016, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql>

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