mysql> SELECT DISTINCT CONCAT('User: ''',user,'''@''',host,''';') AS query FROM mysql.user;
+---------------------------------------+
| query                                 |
+---------------------------------------+
| User: ;                | 
| User: ;              | 
| User: ;                      | 
| User: ;                     | 
| User: ;                    | 
| User: ;                   | 
| User: ;             | 
| User: ;           | 
| User: ;       | 
| User: ;  | 
| User: ;       | 
| User: ;                 | 
| User: ;            | 
| User: ;        | 
| User: ;              | 
| User: ;          | 
| User: ;         | 
| User: ;             | 
| User: ;           | 
| User: ;     | 
| User: ; | 
+---------------------------------------+
21 rows in set (0.01 sec)

查看数据库中具体某个用户的权限
mysql> show grants for ;    
+-------------------------------------------------------------------------------------------------------------------+
| Grants for                                                                                             |
+-------------------------------------------------------------------------------------------------------------------+
| GRANT PROCESS, SUPER ON *.* TO  IDENTIFIED BY PASSWORD '*DAFF917B80E3314B1ABECBA9DF8785AFD342CE89' | 
| GRANT ALL PRIVILEGES ON `cacti`.* TO                                                               | 
+-------------------------------------------------------------------------------------------------------------------+
2 rows in set (0.00 sec)

mysql> select * from mysql.user where user='cactiuser' \G   
*************************** 1. row ***************************
                 Host: %
                 User: cactiuser
             Password: *DAFF917B80E3314B1ABECBA9DF8785AFD342CE89
          Select_priv: N
          Insert_priv: N
          Update_priv: N
          Delete_priv: N
          Create_priv: N
            Drop_priv: N
          Reload_priv: N
        Shutdown_priv: N
         Process_priv: Y
            File_priv: N
           Grant_priv: N
      References_priv: N
           Index_priv: N
           Alter_priv: N
         Show_db_priv: N
           Super_priv: Y
Create_tmp_table_priv: N
     Lock_tables_priv: N
         Execute_priv: N
      Repl_slave_priv: N
     Repl_client_priv: N
     Create_view_priv: N
       Show_view_priv: N
  Create_routine_priv: N
   Alter_routine_priv: N
     Create_user_priv: N
           Event_priv: N
         Trigger_priv: N
             ssl_type: 
           ssl_cipher: 
          x509_issuer: 
         x509_subject: 
        max_questions: 0
          max_updates: 0
      max_connections: 0
 max_user_connections: 0

查看user表结构　需要具体的项可结合表结构来查询
mysql> desc mysql.user;
+-----------------------+-----------------------------------+------+-----+---------+-------+
| Field                 | Type                              | Null | Key | Default | Extra |
+-----------------------+-----------------------------------+------+-----+---------+-------+
| Host                  | char(60)                          | NO   | PRI |         |       | 
| User                  | char(16)                          | NO   | PRI |         |       | 
| Password              | char(41)                          | NO   |     |         |       | 
| Select_priv           | enum('N','Y')                     | NO   |     | N       |       | 
******************
******************
+-----------------------+-----------------------------------+------+-----+---------+-------+
39 rows in set (0.00 sec)